WorldWideScience

Sample records for ceramic superconducting bi

  1. Superconducting glass-ceramics in the Bi-Sr-Ca-Cu-O system

    Science.gov (United States)

    De Guire, Mark R.; Kim, Cheol J.; Bausal, Narottam P.

    1990-01-01

    Differential thermal analysis, XRD, SEM, and resistivity measurements, have been used to study the recrystallization during various heat treatments of a Bi1.5SrCaCu2O(z) glass obtained by rapid quenching from the melt. Heating at 450 C formed the Bi(2+x)Sr(2-x)-CuO(z) solid solution designated 'R'. Between 765 and 845 C, R reacts slowly with the glass to form the 80 K superconductor Bi2(Sr,Ca)3Cu2O(z), together with CuO. Heating for 7 days at the higher temperature, followed by slow cooling, raised the temperature of zero resistance to 77 K.

  2. Phase composition and properties of superconducting ceramics based on Bi1.7Pb0.3Sr2Ca2Cu3O y precursors fabricated by melt quenching in a solar furnace

    Science.gov (United States)

    Gulamova, D. D.; Uskenbaev, D. E.; Fantozzi, G.; Chigvinadze, J. G.; Magradze, O. V.

    2009-06-01

    Production of superconducting ceramics based on precursors with rated composition Bi1.7Pb0.3Sr2Ca2Cu3O y is studied. The precursors are synthesized in a solar furnace by melt rapid quenching. The phase composition of the samples is examined by microstructural and X-ray analyses. The temperature dependences of the resistance and magnetic susceptibility are measured. The influence of the composition and crystal structure of the substrate on texturing in the Bi-Sr-Ca-Cu-O system is studied. It is found that the type of quenching plays a significant role, while the type of substrate is of minor significance.

  3. Surface superconductivity in thin cylindrical Bi nanowire.

    Science.gov (United States)

    Tian, Mingliang; Wang, Jian; Ning, Wei; Mallouk, Thomas E; Chan, Moses H W

    2015-03-11

    The physical origin and the nature of superconductivity in nanostructured Bi remains puzzling. Here, we report transport measurements of individual cylindrical single-crystal Bi nanowires, 20 and 32 nm in diameter. In contrast to nonsuperconducting Bi nanoribbons with two flat surfaces, cylindrical Bi nanowires show superconductivity below 1.3 K. However, their superconducting critical magnetic fields decrease with their diameter, which is the opposite of the expected behavior for thin superconducting wires. Quasiperiodic oscillations of magnetoresistance were observed in perpendicular fields but were not seen in the parallel orientation. These results can be understood by a model of surface superconductivity with an enhanced surface-to-bulk volume in small diameter wires, where the superconductivity originates from the strained surface states of the nanowires due to the surface curvature-induced stress.

  4. Low-temperature Sn-119-Moessbauer study of superconducting Bi4Sr(3.5)Ca(2.5)Cu4Sn(0.015)O(16-y) ceramic (2212 phase)

    Science.gov (United States)

    Nishida, Tetsuaki; Katada, Motomi; Miura, Norio; Deshimaru, Yuichi; Yamazoe, Noboru; Matsumoto, Yasukuni; Takashima, Yoshimasa

    1992-04-01

    The Sn-119-Moessbauer spectra of superconducting Bi4Sr(3.5)Ca(2.5)Cu4Sn(0.015)O(16-y) ceramic (2212 phase, Tc, 77 K), measured between 298 K and 7 K, consist of singlet peaks of Sn(4+) with the deltas and Gammas of -0.01-0.07 and 1.05-1.27 mm/s, respectively. The ln A (absorption area)-vs.-T plot shows that the recoil-free fraction f increases with decreasing temperature, and that the Debye and Einstein temperatures are 340 and 185 K, respectively. The Theta(D) of 340 K suggests that the Sn(4+) is in the BiO5 pyramids. The ln A shows a 'normal' lattice vibration, probably because of the long Cu-O(3) distance and the displacement of O(3).

  5. Superconducting Bi(1.5)Pb(0.5)Sr2Ca2Cu3O(x) ceramics by rapid melt quenching and glass crystallization

    Science.gov (United States)

    Bansal, Narottam P.

    1990-01-01

    The preparation of superconducting Bi(1.5)Pb(0.5)Sr2Ca2Cu3O(x) in the glassy state is described, and the results of a study of its crystallization kinetics are presented. The annealing parameters for transforming the glass into a superconductor containing a large fraction of the high-Tc phase were determined. It was found that prolonged annealing (longer than 10 days) in air at 840 C, followed by slow cooling, results in the Tc of 107.2 K and a sharp transition of 2 K.

  6. Intragrain pinning strength depth dependence of 2223 (Bi,Pb)-based high critical Tc superconducting ceramics made by a vitreous route

    Science.gov (United States)

    Dang, An; Godelaine, P. A.; Vanderbemden, Ph.; Cloots, R.; Ausloos, M.

    1995-04-01

    Campbell's method for measuring the critical current in superconductors has been used to obtain the critical current density and the pinning strength in Bi1.7Pb0.3Sr2Ca2Cu3O10-y ceramics synthesized by a vitreous route. The intragrain critical current is much higher than 105 A/cm2 at 40 K in zero dc magnetic field. A large increase of the pinning strength is observed near the grain surface. The decrease with depth is hyperbolic. The role of the precursors in the synthesis route is emphasized for introducing specific pinning centers. The analysis takes into consideration the ceramics granular nature, i.e., the existence of intergrain and intragrain currents.

  7. Superconductivity of Bi1.6Pbo.4Sr2Ca3Cu4O12

    Institute of Scientific and Technical Information of China (English)

    Atilla Coskun; Ahmet Ekicibil; Bekir Ozgelik

    2002-01-01

    The superconducting ceramics Bi1.6Pbo.4Sr2Ca3Cu4O12 have been prepared by the melt-casting method. A zero resistance temperature at 60 K has been observed. It has been found that the superconducting phase temperature Tc increases with increasing sintering temperature. The effect of Pb content on the superconductivity of the ceramic has been studied. The microstructure of the samplehas been investigated by scanning electron microscopy. Phase analysis has been carried out by x-ray diffraction patterns and energy dispersive analysis through x-ray spectroscopy.

  8. Y-Ba Superconducting Ceramics

    Science.gov (United States)

    Shunbao, Tian; Xiaofei, Li; Tinglian, Wen; Zuxiang, Lin; Shichun, Li; Huijun, Yu

    Polycrystalline Y-Ba-Cu-O superconducting materials have been studied. It was found that chemical composition and processing condition may play an important role in the final structure and superconducting properties. The density has been determined and compared with the calculated value according to the structure model reported by Bell Labs. The grain size and the morphology of the materials were observed by SEM.

  9. Manufacturing of superconductive silver/ceramic composites

    DEFF Research Database (Denmark)

    Seifi, Behrouz; Bech, Jakob Ilsted; Eriksen, Morten

    2000-01-01

    Manufacturing of superconducting metal/ceramic composites is a rather new discipline within materials forming processes. High Temperature SuperConductors, HTSC, are manufactured applying the Oxide-Powder-In-Tube process, OPIT. A ceramic powder containing lead, calcium, bismuth, strontium......, and copper oxides is inserted into a silver tube and reduced by multi-step drawing. These single-filaments are packed in a new silver tube thus forming a multi-filament containing e.g. 37 single-filaments, which is subsequently reduced by drawing and rolling to tapes approximately 0.2 mm thick by 3 mm wide...

  10. Scanning SQUID microscopy of local superconductivity in inhomogeneous combinatorial ceramics.

    Science.gov (United States)

    Iranmanesh, Mitra; Stir, Manuela; Kirtley, John R; Hulliger, Jürg

    2014-11-24

    Although combinatorial solid-state chemistry promises to be an efficient way to search for new superconducting compounds, the problem of determining which compositions are strongly diamagnetic in a mixed-phase sample is challenging. By means of reactions in a system of randomly mixed starting components (Ca, Sr, Ba, La, Y, Pb, Bi, Tl, and Cu oxides), samples were produced that showed an onset of diamagnetic response above 115 K in bulk measurements. Imaging of this diamagnetic response in ceramic samples by scanning SQUID microscopy (SSM) revealed local superconducting areas with sizes down to as small as the spatial resolution of a few micrometers. In addition, locally formed superconducting matter was extracted from mixed-phase samples by magnetic separation. The analysis of single grains (d<80 μm) by X-ray diffraction, elemental analysis, and bulk SQUID measurements allowed Tl2Ca3Ba2Cu4O12, TlCaBaSrCu2O(7-δ), BaPb(0.5)Bi(0.25)Tl(0.25)O(3-δ), TlBa2Ca2Cu3O9, Tl2Ba2CaCu2O8, and YBa2Cu3O7 phases to be identified. SSM, in combination with other diagnostic techniques, is therefore shown to be a useful instrument to analyze inhomogeneous reaction products in the solid-state chemistry of materials showing magnetic properties.

  11. Structural properties of superconducting Bi-2223/Ag tapes

    Energy Technology Data Exchange (ETDEWEB)

    Gottschalck Andersen, L.

    2001-05-01

    The structural properties of silver clad high-T{sub c} superconducting ceramic tapes of (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} (Bi-2223) have been investigated by means of synchrotron X-ray diffraction (including the 3DXRD microscope setup), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDS). By synchrotron X-ray diffraction in situ studies of the phase development during the transformation of (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 1}Cu{sub 2}O{sub x} (Bi-2212) into Bi-2223, the stoichiometry changes and the texture have been performed during annealing in 8% O{sub 2} and in air. Furthermore, an annealing with two high temperature cycles has been performed to study the equilibrium phenomena. During heating (Ca,Sr){sub 2}PbO{sub 4} decomposes at temperatures between 700 deg. C and 840 deg.C. Simultaneously, the Bi-2212 lattice contracts, indicating an incorporation of Pb. Moreover, the grain mis-alignment decreases significantly. In air we have observed that Bi-2212 partly dissociates into (Ca,Sr){sub 2}CuO{sub 3} and a liquid at temperatures above 812 deg. C. At the annealing temperature Bi-2212 and (Ca,Sr){sub 2}CuO{sub 3} react with the liquid to form Bi-2223. The transformation mechanism is discussed. During cooling below {approx}750 deg.C (Ca,Sr){sub 2}CuO{sub 3} and the liquid mainly transform into Bi-2201. Below {approx}780 deg. C Bi-2223 decomposes to 3221. In addition, a two-step cooling experiment and a decomposition study have been performed in 8% O{sub 2}. By TEM the grain and colony size in the c-axis direction, the angles of c-axis tilt grain boundaries and the intergrowth content are investigated. A fully processed tape has on average 50% thicker grains than a tape after the 1st annealing. The angles of c-axis tilt grain boundaries are on average 14 deg. and 26 deg. for the fully processed tape and the tape after the 1st annealing, respectively. The intergrowth content (15%) and

  12. Texturing of superconducting Bi-Pb-Sr-Ca-Cu-O ceramics by combining the effect of a magnetic field and hot pressing in one direction; Texturation des ceramiques supraconductrices Bi-Pb-Sr-Ca-Cu-O par combinaison des effets du champ magnetique et de la contrainte uniaxiale a haute temperature

    Energy Technology Data Exchange (ETDEWEB)

    Noudem, J.G.

    1995-10-27

    Superconducting Bi-(Pb)-Sr-Ca-Cu-O (Bi:2223) ceramics have a weak 77 K transport critical current density (Jc) due to porosity and the presence of misaligned platelets. In order to obtain higher critical current densities in these materials, it is necessary to increase their density and induce a preferential crystallographic orientation. We have developed a texturing process using solidification in a magnetic field combined with hot pressing. The experimental set-up provides a uniaxial pressure of 60 MPa and temperature up to 1100 deg C in a magnetic field of 8 T. Magnetic melt texturing (MMT) proved to be very effective in producing bulk oriented samples of polycrystalline Bi:2223 (crystallite c-axis oriented parallel to the field direction). These samples have Jc values of up to 1450 A/cm{sup 2} and a density of 5.1 g/cm{sup 3}. The texturing by hot pressing (HP) gives homogeneous, dense ({approx} 6 g/cm{sup 3}; 95 % of the theoretical limit) ceramics with a Jc of 2500 A/cm{sup 2}. Tapes of Ag/Bi:2223 provided by Alcatel Alsthom were also successful textured using HP. Finally we have demonstrated that the combination of solidification in a magnetic field with hot pressing (MMHPT) improves both the texture and density of the samples. Moreover the samples are very homogeneous and mechanically resistant. The 77 K transport critical current densities have values up to 3800 A/cm{sup 2} and 1100 A/cm{sup 2} along the (ab) and c-axis respectively. We have demonstrated that these samples are of potential use a current limiters. (author) 146 refs.

  13. Ba2ErNbO6: A new perovskite ceramic substrate for Bi(2223) superconducting thick films (c(0) = 110 K)

    Indian Academy of Sciences (India)

    S U K Nair; P R S Warriar; J Koshy

    2005-02-01

    Barium erbium niobate (Ba2ErNbO6) has been developed as a new substrate for (Bi,Pb)2Sr2Ca2Cu3O [Bi(2223)] superconductor film. Ba2ErNbO6 (BENO) has a cubic perovskite structure with lattice constant, = 8.318 Å. The Bi(2223) superconductor does not show any detectable chemical reaction with BENO even under extreme processing conditions. Dip coated Bi (2223) thick film, Ba2ErNbO6 substrate, gave a c (0) of 110 K and current density of ∼ 4 × 103 A cm-2 at 77 K and zero magnetic field.

  14. Superconducting Bi1.5Pb0.5Sr2Ca2Cu3O(x) ceramics by rapid melt quenching and glass crystallization

    Science.gov (United States)

    Bansal, Narottam P.

    1989-01-01

    A glass of nominal Bi(1.5)Pb(0.5)Sr2Ca2Cu3O(x) composition, prepared by rapid quenching of the melt, showed a glass transition temperature of 383 C, crystallization temperature of 446 C, melting temperature of 855 C, and bulk density of 5.69 g/cu cm in air. The activation energy for crystallization of the glass was estimated to be 292kJ/mol from non-isothermal DSC. On heating in oxygen, the glass showed a slow and continuous weight gain starting at approximately 530 C which reached a plateau at approximately 820 C. The weight gained during heating was retained on cooling to ambient conditions indicating an irreversible oxidation step. The influence of annealing conditions on the formation of various phases in the glass has been investigated. The Bi(2)Sr(2)Ca(0)Cu(1)O(6) phase crystallized out first followed by formation of other phases at higher temperatures. The high-T(sub c) phase, isostructural with Bi(2)Sr(2)Ca(2)Cu(3)O(10) was not detected below 840 C, but its fraction increased with the annealing time at 840 C. A sample annealed at 840 C for 243h in air and furnace cooled showed the highest T(sub c)(R=0) of 107.2K and a narrow transition width, delta T(sub c)(10 to 90 percent), of approximately 2 K. The high T(sub c) phase does not seem to crystallize out directly from the glass but is rather produced at high temperature by reaction between the phases formed at lower temperatures. The kinetics of 110K phase formation was sluggish. It appears that the presence of lead helps in the formation and/or stabilization of the 110 K phase.

  15. Effect of CuF2 on the Synthesis and Superconducting Properties of (Bi,Pb)2Sr2Ca2Cu3O10 Bulk Ceramic Samples

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude; Andersen, Niels Hessel

    2013-01-01

    Bulk polycrystalline samples with Bi1.72Pb0.34Sr1.87Ca1.91Cu3.13O9.83−x F x (0.00≤x≤0.51) were prepared by a solid-state route using CuF2 as a fluorine source. CuF2 was introduced in the precursor powders either by direct mixing with the other starting reagents or by addition to precalcined precu...

  16. Role of vanadium in Bi-2223 ceramics

    Indian Academy of Sciences (India)

    D R Mishra; S V Sharma; R G Sharma

    2000-02-01

    The effect of substitution of vanadium in Bi1.6Pb0.4Sr2Ca2Cu3O ceramic at Bi and Cu sites has been investigated for the resistivity, a.c. susceptibility, XRD and a.c. magnetization studies. Enhancement in for the smaller concentrations of V at either of the two sites was observed which followed an expected lattice distortion and decrease in for higher V concentrations. V plays a role of substituting element more than just a sintering agent as reflected in the more rapid decrease in at Cu-site and further in the magnetization values that are higher compared to the values at the Bisite. It indicates higher magnetization scattering at the Cu site. The results were explained keeping in mind the liquid phase mechanism behind the formation of the 2223 phase and the possibility of magnetic scattering.

  17. Superconductivity in cubic noncentrosymmetric PdBiSe Crystal

    Science.gov (United States)

    Joshi, B.; Thamizhavel, A.; Ramakrishnan, S.

    2015-03-01

    Mixing of spin singlet and spin triplet superconducting pairing state is expected in noncentrosymmetric superconductors (NCS) due to the inherent presence of Rashba-type antisymmetric spin-orbit coupling. Unlike low symmetry (tetragonal or monoclinic) NCS, parity is isotropicaly broken in space for cubic NCS and can additionally lead to the coexistence of magnetic and superconducting state under certain conditions. Motivated with such enriched possibility of unconventional superconducting phases in cubic NCS we are reporting successful formation of single crystalline cubic noncentrosymmetric PdBiSe with lattice parameter a = 6.4316 Å and space group P21 3 (space group no. 198) which undergoes to superconducting transition state below 1.8 K as measured by electrical transport and AC susceptibility measurements. Significant strength of Rashba-type antisymmetric spin-orbit coupling can be expected for PdBiSe due to the presence of high Z (atomic number) elements consequently making it potential candidate for unconventional superconductivity.

  18. Superconductivity in the topological semimetal YPtBi

    Science.gov (United States)

    Butch, Nicholas

    2012-02-01

    Superconductivity was recently discovered in the half Heusler compound YPtBi. Electrical resistivity and Hall data provide compelling evidence that supports the idea that band structure calculations are correct and that YPtBi is indeed a semimetal with nontrivial topology. The low-temperature superconductivity emerges from a remarkable normal state with an extremely low carrier density, no crystalline inversion symmetry, and strong band inversion. I will discuss the normal state properties of YPtBi and details of its superconducting state, and compare them to the characteristics of other potential topological superconductors. This research was performed at the University of Maryland, College Park in collaboration with Paul Syers, Kevin Kirshenbaum, Andrew P. Hope, and Johnpierre Paglione.

  19. Tensile properties and probability of filament fracture in Bi-2223 superconducting tapes

    Energy Technology Data Exchange (ETDEWEB)

    Rabara, Michal [School of Engineering, The University of Tokyo, Tokai-mura, Naka-gun, Ibaraki 319-1106 (Japan). E-mail: rabara at tokai.t.u-tokyo.ac.jp; Sekimura, Naoto [School of Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 117-0033 (Japan); Kitaguchi, Hidetoshi [National Research Institute for Metals, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Kovac, Pavol [Institute of Electrical Engineering, Slovak Academy of Sciences, Dubravskacesta 9, 842 39 Bratislava (Slovakia); Demachi, Kazuyuki; Miya, Kenzo [School of Engineering, The University of Tokyo, Tokai-mura, Naka-gun, Ibaraki 319-1106 (Japan)

    1999-07-01

    Investigation of the mechanical properties of Bi-2223 superconducting tapes was performed by tensile tests. The results show rapid degradation of the critical current after exceeding 0.4% strain. The shape of the I{sub c}=f({epsilon}) curves and the so-called irreversible strain remain identical for various magnetic fields (0-8 T) and temperatures (4.2, 20, 77 K), demonstrating independence of the mechanical properties from these parameters. The superconducting tapes were treated as a composite consisting of a plastic matrix with brittle ceramic fibres. Under uniform tensile load, the probability of the filament fracture follows a Weibull distribution. Its inverse function, the probability of the number of unbroken filaments, is compared with the relative degradation of the critical current obtained from experiment. (author)

  20. Superconductivity in BiS2-based compounds

    Science.gov (United States)

    Yazici, Duygu

    2014-03-01

    Polycrystalline samples of Ln O0.5F0.5BiS2 (Ln = La, Ce, Pr, Nd, Yb) were synthesized by solid-state reaction. These compounds form in a tetragonal structure with space group P 4 / nmm conforming to the CeOBiS2 crystal structure. Electrical resistivity, magnetic susceptibility and specific heat measurements were performed on all of the samples. All of the compounds exhibit superconductivity in the range 1.9 K - 5.4 K, and the YbO0.5F0.5BiS2 sample was also found to exhibit magnetic order (probably antiferromagnetic order) at ~2.7 K that appears to coexist with superconductivity below 5.4 K. Electron-doping appears to induce superconductivity in the BiS2-based superconductors as partial substitution of F for O is necessary to observe superconductivity. This was further demonstrated in a study where trivalent La+3 was partially substituted with tetravalent Th+4, Hf+4, Zr+4, and Ti+4, all of which induced superconductivity. We also observed that substitution of divalent Sr+2 for La+3 (hole doping) does not induce superconductivity. Electrical resistivity measurements were also performed under applied pressure on Ln O0.5F0.5BiS2 (Ln = La, Ce, Pr, Nd) up to ~3 GPa and down to 1 K. These studies revealed a universal behavior where the systems are tuned away from semi-conducting behavior towards metallic behavior. The superconducting states were stabilized by applied pressure, so that Tc increased in all of the rare earth members listed. At a critical pressure Pc, Tc increases rapidly from a low Tc phase to a distinct high Tc phase, after which additional pressure no longer suppressed the semiconducting behavior in the normal state [3,4]. In addition, the metallization of NdO0.5F0.5BiS2 also occurs at Pc. Research was supported by the US AFOSR MURI FA9550-09-1-0603, US DOE DE-FG02-04-ER46105 and NNSA DE-NA0001841.

  1. Design and fabrication of a 30 T superconducting solenoid using overpressure processed Bi2212 round wire

    Energy Technology Data Exchange (ETDEWEB)

    Flanagan, Gene [Muons, Inc., Batavia, IL (United States); Johnson, Rolland [Muons, Inc., Batavia, IL (United States)

    2016-02-18

    High field superconducting magnets are used in particle colliders, fusion energy devices, and spectrometers for medical imaging and advanced materials research. Magnets capable of generating fields of 20-30 T are needed by future accelerator facilities. A 20-30 T magnet will require the use of high-temperature superconductors (HTS) and therefore the challenges of high field HTS magnet development need to be addressed. Superconducting Bi2Sr2CaCu2Ox (Bi2212) conductors fabricated by the oxide-powder-in-tube (OPIT) technique have demonstrated the capability to carry large critical current density of 105 A/cm2 at 4.2 K and in magnetic fields up to 45 T. Available in round wire multi-filamentary form, Bi2212 may allow fabrication of 20-50 T superconducting magnets. Until recently the performance of Bi2212 has been limited by challenges in realizing high current densities (Jc ) in long lengths. This problem now is solved by the National High Magnetic Field Lab using an overpressure (OP) processing technique, which uses external pressure to process the conductor. OP processing also helps remove the ceramic leakage that results when Bi-2212 liquid leaks out from the sheath material and reacts with insulation, coil forms, and flanges. Significant advances have also been achieved in developing novel insulation materials (TiO2 coating) and Ag-Al sheath materials that have higher mechanical strengths than Ag-0.2wt.% Mg, developing heat treatment approaches to broadening the maximum process temperature window, and developing high-strength, mechanical reinforced Bi-2212 cables. In the Phase I work, we leveraged these new opportunities to prototype overpressure processed solenoids and test them in background fields of up to 14 T. Additionally a design of a fully superconducting 30 T solenoid was produced. This work in conjunction with the future path outlined in the Phase II proposal would

  2. The insulating-to-superconducting transition in europium high-temperature superconducting ceramics

    CERN Document Server

    Rosenbaum, R

    1997-01-01

    Experiment resistivity data on high-temperature superconducting ceramics of fully oxygenated EuBa sub 2 Cu sub 3 sub - sub x Co sub x O sub y show that the insulating-to-superconducting transitions take place at liquid-helium temperature, provided that the cobalt fraction x exceeds 0.3. The resistivity follows a simple power-law dependence rho propor to T sup - sup 1 sup / sup 2 , attributed to electron-electron interactions. A model based upon intrinsic Josephson tunnelling junctions is suggested to explain the transition from insulating to superconducting states. (author)

  3. Low-temperature [sup 119]Sn-moessbauer study of superconducting Bi[sub 4]Sr[sub 3. 5]Ca[sub 2. 5]Cu[sub 4]Sn[sub 0. 015]O[sub 16-y] ceramic (2212 phase)

    Energy Technology Data Exchange (ETDEWEB)

    Nishida, Tetsuaki (Kyushu Univ., Fukuoka (Japan). Faculty of Science); Katada, Motomi; Miura, Norio; Deshimaru, Yuichi; Yamazoe, Noboru; Matsumoto, Yasukuni; Takashima, Yoshimasa

    1992-04-01

    The [sup 119]Sn-Moessbauer spectra of superconducting Bi[sub 4]Sr[sub 3.5]Ca[sub 2.5]Cu[sub 4]Sn[sub 0.015]O[sub 16-y] ceramic (2212 phase, T[sub c] : 77 K), measured between 298K and 7K, consist of singlet peaks of Sn[sup 4+] with the [delta]'s and [Gamma]'s of - 0.01 - 0.07 and 1.05 - 1.27 mm[center dot]s[sup -1], respectively. The ln A (absorption area)-vs-T plot shows that the recoil-free fraction f increases with decreasing temperature, and that the Debye and Einstein temperatures are 340 and 185 K, respectively. The [Theta][sub D] of 340 K suggests that the Sn[sup 4+] is in the BiO[sub 5] pyramids. The ln A shows a 'normal' lattice vibration probably because of the long Cu-O(3) distance and the displacement of O(3). (author).

  4. Pressure-induced superconductivity in Bi single crystals

    Science.gov (United States)

    Li, Yufeng; Wang, Enyu; Zhu, Xiyu; Wen, Hai-Hu

    2017-01-01

    Measurements on resistivity and magnetic susceptibility have been carried out for Bi single crystals under pressures up to 10.5 GPa. The temperature dependent resistivity shows a semimetallic behavior at ambient and low pressures (below about 1.6 GPa). This is followed by an upturn of resistivity in the low temperature region when the pressure is increased, which is explained as a semiconductor behavior. This feature gradually gets enhanced up to a pressure of about 2.52 GPa. Then a nonmonotonic temperature dependent resistivity appears upon further increasing pressure, which is accompanied by a strong suppression to the low temperature resistivity upturn. Simultaneously, a superconducting transition occurs at about 3.92 K under a pressure of about 2.63 GPa. With further increasing pressure, a second superconducting transition emerges at about 7 K under about 2.8 GPa. For these two superconducting states, the superconductivity induced magnetic screening volumes are quite large. As the pressure further increases to 8.1 GPa, we observe the third superconducting transition at about 8.2 K. The resistivity measurements under magnetic field allow us to determine the upper critical fields μ0Hc 2 of the superconducting phases. The upper critical field for the phase with Tc=3.92 K is extremely low. Based on the Werthamer-Helfand-Hohenberg (WHH) theory, the estimated value of μ0Hc 2 for this phase is about 0.103 T, while the upper critical field for the phase with Tc=7 K is very high with a value of about 4.56 T. Finally, we present a pressure dependent phase diagram of Bi single crystals. Our results reveal the interesting and rich physics in bismuth single crystals under high pressure.

  5. Magnetic field expulsion in superconducting granular ceramics and in polymer/superconductor composites

    Energy Technology Data Exchange (ETDEWEB)

    Benlhachemi, A. [Univ. de Toulon et du Var, La Garde (France). Lab. des Materiaux Multiphases et Interfaces]|[Lab. de Chimie des Solides, Faculte des Sciences, Univ. Ibnou Zohr, Agadir (Morocco); Fremy, M.A.; Breandon, C.; Tatarenko, H.; Gavarri, J.R. [Univ. de Toulon et du Var, La Garde (France). Lab. des Materiaux Multiphases et Interfaces; Benyaich, H. [Lab. de Chimie des Solides, Faculte des Sciences, Univ. Ibnou Zohr, Agadir (Morocco)

    1998-05-01

    The magnetic interaction between a permanent magnet and superconducting ceramics such as YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} and Bi{sub 1.6}Pb{sub 0.4}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub (10+} {sub de} {sub lta)} depend on the superconducting state of each phase and on the junctions between grains. In the case of polymer/superconductor composites, screening effects depend on the volume fraction of superconductor. Measurements of the evolution of the levitation force (F=A/d{sup {gamma}}) as a function of the interaction distance d are used to characterize the effective response of the ceramics or composites to the magnetic flux penetration. Some of the abnormal variations of the exponent {gamma} and of the term A (in F=A/d{sup {gamma}}) could be reinterpreted in terms of a change in superconducting regime. Other observed variations of {gamma} should be due to the variation of the effective field from the cylindrical magnet. (orig.) 19 refs.

  6. Superconductivity of Bi Confined in an Opal Host

    Science.gov (United States)

    Johnson, R. C.; Nieskoski, M. D.; Disseler, S. M.; Huber, T. E.; Graf, M. J.

    2013-02-01

    Superconductivity is observed in a composite of rhombohedral crystalline bismuth nanoparticles imbedded in an insulating porous opal host via electrical transport and AC magnetic susceptibility. The onset of superconductivity in this system occurs in two steps, with upper transition temperature T c, U =4.1 K and lower transition temperature of T c, L =0.7 K, which we attribute to the granular nature of the composite. The transition at T c, U is observed to split into two transitions with the application of a magnetic field, and these have upper critical fields extrapolated to T=0 K of H c2,1(0)=0.7 T and H c2,2(0)=1.0 T, corresponding to coherence lengths of ξ 1(0)=21 nm and ξ 2(0)=18 nm, respectively. We suggest that because of the lack of bulk-like states in the Bi nanoparticles due to confinement effects, superconductivity originates from surface states arising from Rashba spin-orbit scattering at the interface.

  7. Commercial Process of Bi-based 2212 Single Phase Superconducting Precursor Powder

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Laying emphasis on the preparation of Bi-based 2212 single phase superconducting powder, some technological parameters, which effect the single phase degree and uniformity of powder, such as prebaking, sintering and heat treatment were investigated and discussed. Ensuring the powder Tc at 83~85 K, the crucial impurity carbon was reduced to 0.03% and less. Adopting uncommon technique made the powder size to micrometer level, meanwhile the superconducting performance of the powder was unchanged. The fine superconducting powder was characterized. This process of Bi-based 2212 superconducting powder was successful.

  8. Superconductivity in Ba(Pb,Bi,Sb)O 3, Ba(Pb,Bi,Te)O 3 and (Ba,La) (Pb,Bi,Tl)O 3 systems

    Science.gov (United States)

    Nagarajan, R.; Vasanthacharya, N. Y.; Gopalakrishnan, J.; Rao, C. N. R.

    1991-02-01

    It is possible to substitute Bi in the superconducting BaPb 0.75Bi 0.25O 3 by Sb or Te without destroying the superconductivity. With Sb, a continuous series of solid solutions BaPb 0.75Bi 0.25-ySb yO 3 (0 ⩽ y ⩽ 0.25) exists, while with Te, perovskite BaPb 0.75Bi 0.25-yTe yO 3 exists only upto y = 0.15. With increasing substitution by Sb or Te, T c decreases continously in both the systems. Superconductivity with a maximum T c of 8K is found in Ba 0.9La 0.1Pb 0.9-yBi yTl 0.1O 3 for y = 0.25.

  9. Stacking variants and superconductivity in the Bi-O-S system.

    Science.gov (United States)

    Phelan, W Adam; Wallace, David C; Arpino, Kathryn E; Neilson, James R; Livi, Kenneth J; Seabourne, Che R; Scott, Andrew J; McQueen, Tyrel M

    2013-04-10

    High-temperature superconductivity has a range of applications from sensors to energy distribution. Recent reports of this phenomenon in compounds containing electronically active BiS2 layers have the potential to open a new chapter in the field of superconductivity. Here we report the identification and basic properties of two new ternary Bi-O-S compounds, Bi2OS2 and Bi3O2S3. The former is non-superconducting; the latter likely explains the superconductivity at T(c) = 4.5 K previously reported in "Bi4O4S3". The superconductivity of Bi3O2S3 is found to be sensitive to the number of Bi2OS2-like stacking faults; fewer faults correlate with increases in the Meissner shielding fractions and T(c). Elucidation of the electronic consequences of these stacking faults may be key to the understanding of electronic conductivity and superconductivity which occurs in a nominally valence-precise compound.

  10. Intercalated Nanocomposites Based on High-Temperature Superconducting Ceramics and Their Properties

    Directory of Open Access Journals (Sweden)

    Sevan Davtyan

    2009-12-01

    Full Text Available High temperature superconducting (SC nanocomposites based on SC ceramics and various polymeric binders were prepared. Regardless of the size of the ceramics’ grains, the increase of their amount leads to an increase of resistance to rupture and modulus and a decrease in limiting deformation, whereas an increase in the average ceramic grain size worsens resistance properties. The SC, thermo-chemical, mechanical and dynamic-mechanical properties of the samples were investigated. Superconducting properties of the polymer ceramic nanocomposites are explained by intercalation of macromolecule fragments into the interstitial layer of the ceramics’ grains. This phenomenon leads to a change in the morphological structure of the superconducting nanocomposites.

  11. Optimization of Rolling Process for Bi(2223)/Ag Superconducting Tapes by a Statistical Method

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Ag-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox tapes were prepared by the powder-in-tube method. The influences of rolling parameters on superconducting characteristics of Bi(2223)/Ag tapes were analyzed qualitatively with a statistical method. The results demonstrate that roll diameter and reduction per pass significantly influence the properties of superconducting tapes while roll speed does less and working friction the least. An optimized rolling process was therefore achieved according to the above results.

  12. Properties of superconducting Bi-Sr-Ca-Cu-O system remelted under higher gravity conditions

    Science.gov (United States)

    Volkov, M. P.; Melekh, B. T.; Parfeniev, R. V.; Kartenko, N. F.; Regel, L. L.; Turchaninov, A. M.

    1992-04-01

    The structure and magnetic properties of high Tc superconductor Bi-Sr-Ca-Cu-O samples remelted under 1 g0, 8 g0 and 12 g0 gravity levels have been investigated. Superconducting properties make a change along the ingots. The dependence of structural and superconducting properties on the gravity level and their time degradation have been observed.

  13. Effect of pelletization pressure on structural properties and critical current hysteresis of ceramic superconducting Bi sub 1 sub . sub 7 Pb sub 0 sub . sub 3 Sr sub 2 Ca sub 2 Cu sub 3 O sub y

    CERN Document Server

    Tepe, M; Abukay, D

    2003-01-01

    The effect of pelletization pressures on structural properties and critical current hysteresis of Bi sub 1 sub . sub 7 Pb sub 0 sub . sub 3 Sr sub 2 Ca sub 2 Cu sub 3 O sub y samples was investigated. The samples used in this study were prepared by classical solid-state reaction at the pressures from 100 up to 500 MPa. The obtained samples were characterized by resistance vs. temperature, (R-T), critical current density vs. applied magnetic field, (J sub c -H), material density vs. pressure, (rho-P), XRD, SEM, and EDAX. The results of this study showed that the quality of electrical and structural properties of Bi-2223 bulk superconductors strongly depends on the pelletization pressure. Pressing of bulk samples at 400 MPa produces textured grain alignment and associates microstructural modifications in order to enhance flux pinning and thus increases current carrying capacities. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  14. Hydrostatic pressure effect on the superconducting properties of BaBi3 and SrBi3 single crystals

    Science.gov (United States)

    Jha, Rajveer; Avila, Marcos A.; Ribeiro, Raquel A.

    2017-02-01

    We demonstrate the superconducting properties of, and hydrostatic pressure effect on, BaBi3 and SrBi3 superconductors. We measure the dc magnetic susceptibility under hydrostatic pressure for both compounds, which shows a positive pressure coefficient of dT c/dP = 1.22 K GPa-1 for BaBi3 and a negative pressure coefficient of dT c/dP = -0.43 K GPa-1 for SrBi3. The normal state electrical resistivity shows that both compounds are highly metallic in nature. The upper critical fields H c2 evaluated by resistivity under magnetic fields ρ(T,H) are 22 kOe for BaBi3 and 2.9 kOe for SrBi3. A specific heat jump of ΔC e/γT c = 1.05 suggests weak coupling superconductivity in BaBi3, whereas ΔC e/γT c = 2.08 for SrBi3 is higher than the Bardeen-Cooper-Schrieffer theory value of 1.43, indicating a strong coupling superconductor.

  15. Development of a persistent superconducting joint between Bi-2212/Ag-alloy multifilamentary round wires

    Science.gov (United States)

    Chen, Peng; Trociewitz, Ulf P.; Davis, Daniel S.; Bosque, Ernesto S.; Hilton, David K.; Kim, Youngjae; Abraimov, Dmytro V.; Starch, William L.; Jiang, Jianyi; Hellstrom, Eric E.; Larbalestier, David C.

    2017-02-01

    Superconducting joints are one of the key components needed to make Ag-alloy clad Bi2Sr2CaCu2O8+x (Bi-2212) superconducting round wire (RW) successful for high-field, high-homogeneity magnet applications, especially for nuclear magnetic resonance magnets in which persistent current mode operation is highly desired. In this study, a procedure for fabricating superconducting joints between Bi-2212 RWs during coil reaction was developed. Melting temperatures of Bi-2212 powder with different amounts of Ag addition were investigated by differential thermal analysis so as to provide information for selecting the proper joint matrix. Test joints of 1.3 mm dia. wires heat treated in 1 bar flowing oxygen using the typical partial melt Bi-2212 heat treatment (HT) had transport critical currents I c of ˜900 A at 4.2 K and self-field, decreasing to ˜480 A at 14 T evaluated at 0.1 μV cm-1 at 4.2 K. Compared to the I c of the open-ended short conductor samples with identical 1 bar HT, the I c values of the superconducting joint are ˜20% smaller than that of conductor samples measured in parallel field but ˜20% larger than conductor samples measured in perpendicular field. Microstructures examined by scanning electron microscopy clearly showed the formation of a superconducting Bi-2212 interface between the two Bi-2212 RWs. Furthermore, a Bi-2212 RW closed-loop solenoid with a superconducting joint heat treated in 1 bar flowing oxygen showed an estimated joint resistance below 5 × 10-12 Ω based on its field decay rate. This value is sufficiently low to demonstrate the potential for persistent operation of large inductance Bi-2212 coils.

  16. Superconductivity in the high-Tc Bi-Ca-Sr-Cu-O system - Phase identification

    Science.gov (United States)

    Hazen, R. M.; Prewitt, C. T.; Angel, R. J.; Ross, N. L.; Finger, L. W.

    1988-01-01

    Four phases are observed in superconducting Bi-Ca-Sr-Cu-O samples. The superconducting phase, with onset temperature near 120 K, is a 15.4-A-layered compound with composition near Bi2Ca1Sr2Cu2O9 and an A-centered orthorhombic unit subcell 5.41 x 5.44 x 30.78 A. X-ray diffraction and electron microscopy data are consistent with a structure of alternating perovskite and Bi2O2 layers. High-resolution transmission electron microscopy images reveal a b-axis superstructure of 27.2 A, numerous (001) stacking faults, and other defects.

  17. Pressure-induced superconductivity in the giant Rashba system BiTeI

    Science.gov (United States)

    VanGennep, D.; Linscheid, A.; Jackson, D. E.; Weir, S. T.; Vohra, Y. K.; Berger, H.; Stewart, G. R.; Hennig, R. G.; Hirschfeld, P. J.; Hamlin, J. J.

    2017-03-01

    At ambient pressure, BiTeI exhibits a giant Rashba splitting of the bulk electronic bands. At low pressures, BiTeI undergoes a transition from trivial insulator to topological insulator. At still higher pressures, two structural transitions are known to occur. We have carried out a series of electrical resistivity and AC magnetic susceptibility measurements on BiTeI at pressure up to  ∼40 GPa in an effort to characterize the properties of the high-pressure phases. A previous calculation found that the high-pressure orthorhombic P4/nmm structure BiTeI is a metal. We find that this structure is superconducting with T c values as high as 6 K. AC magnetic susceptibility measurements support the bulk nature of the superconductivity. Using electronic structure and phonon calculations, we compute T c and find that our data is consistent with phonon-mediated superconductivity.

  18. Superconductivity in the amorphous phase of topological insulator Bi x Sb100-x alloys

    Science.gov (United States)

    Barzola-Quiquia, J.; Lauinger, C.; Zoraghi, M.; Stiller, M.; Sharma, S.; Häussler, P.

    2017-01-01

    In this work we investigated the electrical properties of rapidly quenched amorphous Bi x Sb{}100-x alloys in the temperature range of 1.2 K to 345 K. The resistance reveals that for a broad range of different compositions, including that for the topological insulator (TI), a superconducting state in the amorphous phase is present. After crystallization and annealing at an intermediate temperature, we found that in pure Bi and Bi x Sb{}100-x alloys with composition corresponding to the TI, the superconductivity persists, but the transition shifts to a lower temperature. The highest superconducting transition temperature {T}{{C}0} was found for pure Bi and those TI’s, with a shift to low temperatures when the Sb content is increased. After annealing at a maximum temperature of T = 345 K, the samples are non-superconducting within the experimental range and the behavior changes from semiconducting-like for pure Bi, to metallic-like for pure Sb. Transition temperature {T}{{C}0} of the amorphous Bi x Sb{}100-x alloys have been calculated in the BCS-Eliashberg-McMillan framework, modified for binary alloys. The results can explain the experimental results and show that amorphous Bi x Sb{}100-x exhibits a strong to intermediate electron-phonon coupling.

  19. Anionic conducting oxide ceramics: Microstructure - property relations of BiCuVOx ceramics. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Berrera, T.P.; Dunn, B.; Fuqua, P.D.; Leininger, J.; Mackenzie, J.D.

    1996-06-14

    The bismuth vanadate composition, Bi4V2O11, is the parent compound for a new family of oxygen ion conductors. The substitution of various metallic ions for vanadium stabilizes the high temperature gamma-phase and leads to a series of compounds which possess the highest oxygen ion conductivities observed for temperatures below 400 deg C. This paper reports the first studies on the processing, densification and transport properties of copper-doped bismuth vanadate ceramics. Phase-pure materials with densities above 95% of theoretical were obtained using standard ceramic processing approaches. Ionic conductivities in the range of 1 x 10(exp {minus}2) S/cm at 400 deg C were observed for a variety of sintered samples.

  20. Bismuthates: BaBiO{sub 3} and related superconducting phases

    Energy Technology Data Exchange (ETDEWEB)

    Sleight, Arthur W., E-mail: arthur.sleight@oregonstate.edu

    2015-07-15

    Highlights: • BaBiO{sub 3} has the perovskite structure, but tilting of the BiO{sub 6} octahedra destroy the ideal cubic symmetry except at temperatures above 820 K. BaBiO{sub 3} is a diamagnetic semiconductor due to a CDW, which is equivalent to a Ba{sub 2}Bi{sup 3+}Bi{sup 5+}O{sub 6} representation. • Recent calculations and experimental results confirm that there is no significant deviation from the oxidation states of 3+ and 5+. • Superconductivity with a T{sub c} as high as 13 K occurs for BaPb{sub 1−x}Bi{sub x}O{sub 3} phases where the 6s band is about 25% filled, and superconductivity with a T{sub c} as high as 34 K occurs for Ba{sub 1−x}K{sub x}BiO{sub 3} phases where the 6s band is about 35% filled. • These two solid solutions can have cubic, tetragonal, or orthorhombic symmetry. • However, superconductivity has only been observed when the symmetry is tetragonal. - Abstract: BaBiO{sub 3} has the perovskite structure, but tilting of the BiO{sub 6} octahedra destroy the ideal cubic symmetry except at temperatures above 820 K. BaBiO{sub 3} is a diamagnetic semiconductor due to a charge density wave (CDW), which is equivalent to a Ba{sub 2}Bi{sup 3+}Bi{sup 5+}O{sub 6} representation. Recent calculations and experimental results confirm that there is no significant deviation from the oxidation states of 3+ and 5+. Superconductivity with a T{sub c} as high as 13 K occurs for BaPb{sub 1−x}Bi{sub x}O{sub 3} phases where the 6s band is about 25% filled, and superconductivity with a T{sub c} as high as 34 K occurs for Ba{sub 1−x}K{sub x}BiO{sub 3} phases where the 6s band is about 35% filled. Structures in these two solid solutions can have cubic, tetragonal, orthorhombic, or monoclinic symmetry. However, superconductivity has only been observed when the symmetry is tetragonal.

  1. SYNTHESIS AND CHARACTERIZATIONS OF PURE AND DOPED NANOCRYSTALLINE BiFeO3 CERAMICS BY SHS

    Directory of Open Access Journals (Sweden)

    YOGESH A. CHAUDHARI

    2014-03-01

    Full Text Available The pure and Zn incorporated BiFeO3 ceramics were synthesized by self-propagating high temperature synthesis (SHS. The X-ray diffractometer (XRD studies revealed that, both BiFeO3 and BiFe0.95Zn0.05O3 ceramics crystallizes in a single phase rhombhohedral structure. The room temperature ferroelectric and magnetic hysteresis loop evidenced coexistence of ferroelectricity and magnetism in single phase undoped and Zn doped BiFeO3. The M-H hysteresis loop of BiFe0.95Zn0.05O3 sample demonstrated a weak ferromagnetism at 300 K and 5 K respectively. The room temperature ferroelectric P-E hysteresis loops of BiFeO3 and BiFe0.95Zn0.05O3 exhibited an unsaturated behavior and suggests a partial reversal of polarization. A variation of dielectric constant with respect to temperature in BiFeO3 and BiFe0.95Zn0.05O3 ceramic delivers a dielectric anomaly around 480 and 450°C which is a consequence of antiferromagnetic to paramagnetic phase transition (TN. Moreover, for BiFeO3 the anomaly manifests a possible coupling between electric and magnetic dipole moments.

  2. Properties of superconducting Bi-Sr-Ca-Cu-O system remelted under higher gravity conditions

    Energy Technology Data Exchange (ETDEWEB)

    Volkov, M.P.; Melekh, B.T.; Parfeniev, R.V.; Kartenko, N.F. (A.F. Ioffe Physical Technical Inst., Academy of Sciences, Moscow (Russia)); Regel, L.L.; Turchaninov, A.M. (Space Research Inst., Academy of Sciences, Moscow (Russia))

    1992-04-01

    The structure and magnetic properties of high Tc superconductor Bi-Sr-Ca-Cu-O samples remelted under 1g{sub 0}, 8g{sub 0} and 12g{sub 0} gravity levels have been investigated. Superconducting properties make a change along the ingots. The dependence of structural and superconducting properties on the gravity level and their time degradation have been observed. (orig.).

  3. Superconductivity with two-fold symmetry in topological superconductor Sr x Bi2Se3

    Science.gov (United States)

    Du, Guan; Li, YuFeng; Schneeloch, J.; Zhong, R. D.; Gu, GenDa; Yang, Huan; Lin, Hai; Wen, Hai-Hu

    2017-03-01

    Topological superconductivity is the quantum condensate of paired electrons with an odd parity of the pairing function. By using a Corbino-shape like electrode configuration, we measure the c-axis resistivity of the recently discovered superconductor Sr x Bi2Se3 with the magnetic field rotating within the basal planes, and find clear evidence of two-fold superconductivity. The Laue diffraction measurements on these samples show that the maximum gap direction is either parallel or perpendicular to the main crystallographic axis. This observation is consistent with the theoretical prediction and strongly suggests that Sr x Bi2Se3 is a topological superconductor.

  4. Dielectric Properties of Bi4Ti3O12 Ceramics by Impedance Spectroscopic Method

    Institute of Scientific and Technical Information of China (English)

    CHEN Yong; SU Huyin; XUE Simin; LI Zhaozhi; ZHANG Cancan; CHEN Qi; XU Lingfang; CAO Wanqiang; HUANG Zhaoxiang

    2016-01-01

    Various lead-free ceramics have been investigated in search for new high-temperature dielectrics. In particular, Bi4Ti3O12 is a type of ferroelectric ceramics, which is supposed to replace lead-containing ceramics for its outstanding dielectric properties in the near future. Ferroelectric ceramics of Bi4Ti3O12 made by conventional mixed oxide route have been studied by impedance spectroscopy in a wide range of temperature. X-ray diffraction patterns show that Bi4Ti3O12 ceramics are a single-phase of ferroelectric Bi-layered perovskite structure whether it is calcined at 800℃ or after sintering production. This study focused on the effect of the grain size on the electric properties of BIT ceramics. The BIT ceramics with different grain sizes were prepared at different sintering temperatures. Grain becomes coarser with the sintering temperature increasing by 50℃, relative permittivity and dielectric loss also change a lot. When sintered at 1 100℃, r values peak can reach 205.40 at a frequency of 100 kHz, the minimum dielectric losses of four different frequencies make no difference, all close to 0.027. The values ofEa range from 0.52 to 0.68 eV. The dielectric properties of the sample sintered at 1 100℃ are relatively better than those of the other samples by analyzing the relationship of the grain, the internal stresses, the homogeneity and the dielectric properties. SEM can better explain the results of the dielectric spectrum at different sintering temperatures. The results show that Bi4Ti3O12 ceramics are a kind of dielectrics. Thus, Bi4Ti3O12 can be used in high-temperature capacitors and microwave ceramics.

  5. Reversibility of Superconductivity in CuxBi2Se3 via Quenching Conditions

    Science.gov (United States)

    Schneeloch, John; Zhong, Ruidan; Xu, Zhijun; Yang, Alina; Gu, Genda; Tranquada, John

    2013-03-01

    We investigated the effect of various growth and annealing conditions on Cu0.3Bi2Se3, a compound proposed to host topological superconductivity. For annealing temperature T >580° C, quenching was found necessary for superconductivity, and the superconductivity loss due to not quenching after annealing was reversible by further annealing and quenching. For T <580° C, annealing was detrimental, even when followed by quenching. Floating zone growth and the annealing of thin (< 1 mm) crystals were found to be detrimental to superconductivity. J. S., Z. X., and R. Z. are supported by the Center for Emergent Superconductivity, an Energy Frontier Research Consortium supported by the Office of Basic Energy Science of the Department of Energy.

  6. SHEAR BOND STRENGTHS BETWEEN CERAMIC CORES AND VENEERING CERAMICS OF DENTAL BI-LAYERED CERAMIC SYSTEMS AND THE SENSITIVITY TO THERMOCYCLING

    Directory of Open Access Journals (Sweden)

    SUN TING, BDS, DDS

    2012-09-01

    Full Text Available The purpose of this study was to investigate the bond strength between various commercial ceramic core materials and veneering ceramics of dental bi-layered ceramic combinations and the effect of thermocycling. The shear bond strength of four dental bi-layered ceramic combinations (white Cercon, yellow Cercon, white Lava, yellow Lava, IPS E.max were tested. Metal ceramic combinations were conducted as a control group. Half of each group was subjected to thermocycling. All specimens were thereafter subjected to a shear force. The initial mean shear bond strength values in MPa ± S.D were 28.02 ± 3.04 for White Cercon Base/Cercon Ceram Kiss, 27.54 ± 2.20 for Yellow Cercon Base/Cercon Ceram Kiss, 28.43 ± 2.13for White Lava Frame/Lava Ceram, 27.36 ± 2.25 for Yellow Lava Frame/Lava Ceram, 47.10 ± 3.77 for IPS E.max Press/IPS E.max Ceram and 30.11 ± 2.15 for metal ceramic control. The highest shear strength was recorded for IPS E.max Press/IPS E.max Ceram before and after thermocycling. The mean shear bond strength values of five other combinations were not significantly different (P < 0.05. Lithium-disilicate based combinations produced the highest core-veneer bonds that overwhelmed the metal ceramic combinations. Thermocycling had no effect on the core-veneer bonds. The core-veneer bonds of zirconia based combinations were not weakened by the addition of coloring pigments.

  7. Superconductivity in the doped topological insulator CuxBi2Se3 under high pressure

    NARCIS (Netherlands)

    Bay, T.V.; Naka, T.; Huang, Y.K.; Luigjes, H.; Golden, M.S.; de Visser, A.

    2012-01-01

    We report a high-pressure single crystal study of the topological superconductor CuxBi2Se3. Resistivity measurements under pressure show superconductivity is depressed smoothly. At the same time the metallic behavior is gradually lost. The upper-critical field data Bc2(T) under pressure collapse ont

  8. Two-Dimensional Superconductivity Emerged at Monatomic Bi(2-) Square Net in Layered Y2O2Bi via Oxygen Incorporation.

    Science.gov (United States)

    Sei, Ryosuke; Kitani, Suguru; Fukumura, Tomoteru; Kawaji, Hitoshi; Hasegawa, Tetsuya

    2016-09-07

    Discovery of layered superconductors such as cuprates and iron-based compounds has unveiled new science and compounds. In these superconductors, quasi-two-dimensional layers including transition metal cations play principal role in the superconductivity via carrier doping by means of aliovalent-ion substitution. Here, we report on a two-dimensional superconductivity at 2 K in ThCr2Si2-type layered oxide Y2O2Bi possessing conducting monatomic Bi(2-) square net, possibly associated with an exotic superconductivity. The superconductivity emerges only in excessively oxygen-incorporated Y2O2Bi with expanded inter-net distance, in stark contrast to nonsuperconducting pristine Y2O2Bi reported previously. This result suggests that the element incorporation into hidden interstitial site could be an alternative approach to conventional substitution and intercalation methods for search of novel superconductors.

  9. Site selectivity on chalcogen atoms in superconducting La(O,F)BiSSe

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Masashi, E-mail: Tanaka.Masashi@nims.go.jp; Matsushita, Yoshitaka; Fujioka, Masaya; Denholme, Saleem J.; Yamaguchi, Takahide; Takeya, Hiroyuki [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Yamaki, Takuma; Takano, Yoshihiko [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577 (Japan)

    2015-03-16

    Single crystals of La(O,F)BiSSe were grown by using a CsCl flux method. Single crystal X-ray structural analysis reveals that the crystal structure is isostructural to the BiS{sub 2}- or BiSe{sub 2}-based compounds crystallizing with space group P4/nmm (lattice parameters a = 4.1110(2) Å, c = 13.6010(7) Å). However, the S atoms are selectively occupied at the apical site of the Bi-SSe pyramids in the superconducting layer. The single crystals show a superconducting transition at around 4.2 K in the magnetic susceptibility and resistivity measurements. The superconducting anisotropic parameter is determined to be 34–35 from its upper critical magnetic field. The anisotropy is in the same range with that of other members of the La(O,F)BiCh{sub 2} (Ch = S, Se) family under ambient pressure.

  10. Dependence of superconductivity in CuxBi2Se3 on quenching conditions

    Science.gov (United States)

    Schneeloch, J. A.; Zhong, R. D.; Xu, Z. J.; Gu, G. D.; Tranquada, J. M.

    2015-04-01

    Topological superconductivity, implying gapless protected surface states, has recently been proposed to exist in the compound CuxBi2Se3 . Unfortunately, low diamagnetic shielding fractions and considerable inhomogeneity have been reported in this compound. In an attempt to understand and improve on the finite superconducting volume fractions, we have investigated the effects of various growth and postannealing conditions. With a melt-growth (MG) method, diamagnetic shielding fractions of up to 56% in Cu0.3Bi2Se3 have been obtained, the highest value reported for this method. We investigate the efficacy of various quenching and annealing conditions, finding that quenching from temperatures above 560∘C is essential for superconductivity, whereas quenching from lower temperatures or not quenching at all is detrimental. A modified floating zone (FZ) method yielded large single crystals but little superconductivity. Even after annealing and quenching, FZ-grown samples had much less chance of being superconducting than MG-grown samples. From the low shielding fractions in FZ-grown samples and the quenching dependence, we suggest that a metastable secondary phase having a small volume fraction in most of the samples may be responsible for the superconductivity.

  11. Thermodynamic evidence for nematic superconductivity in CuxBi2Se3

    Science.gov (United States)

    Yonezawa, Shingo; Tajiri, Kengo; Nakata, Suguru; Nagai, Yuki; Wang, Zhiwei; Segawa, Kouji; Ando, Yoichi; Maeno, Yoshiteru

    2016-10-01

    In condensed matter physics, spontaneous symmetry breaking has been a key concept, and discoveries of new types of broken symmetries have greatly increased our understanding of matter. Recently, electronic nematicity, novel spontaneous rotational-symmetry breaking leading to an emergence of a special direction in electron liquids, has been attracting significant attention. Here, we show bulk thermodynamic evidence for nematic superconductivity, in which the nematicity emerges in the superconducting gap amplitude, in CuxBi2Se3. Based on high-resolution calorimetry of single-crystalline samples under accurate two-axis control of the magnetic field direction, we discovered clear two-fold symmetry in the specific heat and in the upper critical field despite the trigonal symmetry of the lattice. Nematic superconductivity for this material should possess a unique topological nature associated with odd parity. Thus, our findings establish a new class of spontaneously symmetry-broken states of matter--namely, odd-parity nematic superconductivity.

  12. Spin-rotation symmetry breaking in the superconducting state of CuxBi2Se3

    Science.gov (United States)

    Matano, K.; Kriener, M.; Segawa, K.; Ando, Y.; Zheng, Guo-Qing

    2016-09-01

    Spontaneous symmetry breaking is an important concept for understanding physics ranging from the elementary particles to states of matter. For example, the superconducting state breaks global gauge symmetry, and unconventional superconductors can break further symmetries. In particular, spin-rotational symmetry is expected to be broken in spin-triplet superconductors. However, experimental evidence for such symmetry breaking has not been conclusively obtained so far in any candidate compounds. Here, using 77Se nuclear magnetic resonance measurements, we show that spin-rotation symmetry is spontaneously broken in the hexagonal plane of the electron-doped topological insulator Cu0.3Bi2Se3 below the superconducting transition temperature Tc = 3.4 K. Our results not only establish spin-triplet superconductivity in this compound, but may also serve to lay a foundation for the research of topological superconductivity.

  13. Structures, Phase Transformations, and Dielectric Properties of BiTaO4 Ceramics.

    Science.gov (United States)

    Zhou, Di; Fan, Xiao-Qin; Jin, Xiao-Wei; He, Duan-Wei; Chen, Guo-Hua

    2016-11-21

    Low (α)- and high-temperature (β) forms of BiTaO4 have attracted much attention due to their dielectric and photocatalytic properties. In the present work, a third form, the so-called HP-BiTaO4, was synthesized at high temperature and pressure. The phase evolution, phase transformations, and dielectric properties of α- and β-BiTaO4 and HP-BiTaO4 ceramics are studied in detail. β-BiTaO4 ceramics densified at 1300 °C with the microwave permittivity εr ≈ 53, the microwave quality factor Qf ≈ 12070 GHz, and the temperature coefficient of resonant frequency τf ≈ -200 ppm/°C. HP-BiTaO4 ceramics were synthesized at 5 GPa and 1300 °C followed by annealing at 600 °C. In contrast with the α phase, HP-BiTaO4 exhibited εr ≈ 195 at 1 kHz to 10 MHz, accompanied by a low dielectric loss of ∼0.004. The relation between structure and dielectric properties is discussed in the context of Shannon's additive rule and bond theory.

  14. Weak antilocalization effect and noncentrosymmetric superconductivity in a topologically nontrivial semimetal LuPdBi

    KAUST Repository

    Xu, Guizhou

    2014-07-21

    A large number of half-Heusler compounds have been recently proposed as three-dimensional (3D) topological insulators (TIs) with tunable physical properties. However, no transport measurements associated with the topological surface states have been observed in these half-Heusler candidates due to the dominating contribution from bulk electrical conductance. Here we show that, by reducing the mobility of bulk carriers, a two-dimensional (2D) weak antilocalization (WAL) effect, one of the hallmarks of topological surface states, was experimentally revealed from the tilted magnetic field dependence of magnetoconductance in a topologically nontrivial semimetal LuPdBi. Besides the observation of a 2D WAL effect, a superconducting transition was revealed at T c ∼ 1.7â.K in the same bulk LuPdBi. Quantitative analysis within the framework of a generalized BCS theory leads to the conclusion that the noncentrosymmetric superconductivity of LuPdBi is fully gapped with a possibly unconventional pairing character. The co-existence of superconductivity and the transport signature of topological surface states in the same bulk alloy suggests that LuPdBi represents a very promising candidate as a topological superconductor.

  15. Crystalline instability of Bi-2212 superconducting whiskers near room temperature

    Science.gov (United States)

    Cagliero, Stefano; Agostino, Angelo; Khan, Mohammad Mizanur Rahman; Truccato, Marco; Orsini, Francesco; Marinone, Massimo; Poletti, Giulio; Lascialfari, Alessandro

    2009-05-01

    We report new evidences for the thermodynamic instability of whisker crystals in the Bi-Sr-Ca-Cu-O (BSCCO) system. Annealing treatments at 90°C have been performed on two sets of samples, which were monitored by means of X-Rays Diffraction (XRD) and Atomic Force Microscopy (AFM) measurements, respectively. Two main crystalline domains of Bi2Sr2CuCa2O8+ x (Bi-2212) were identified in the samples by the XRD data, which underwent an evident crystalline segregation after about 60 hours. Very fast dynamics of the surface modifications was also described by the AFM monitoring. Two typologies of surface structures formed after about 3 annealing hours: continuous arrays of dome shaped bodies were observed along the edges of the whiskers, while in the central regions a dense texture of flat bodies was found. These modifications are described in terms of the formation of simple oxide clusters involving a degradation of the internal layers.

  16. Topological quantum phase transition and superconductivity induced by pressure in the bismuth tellurohalide BiTeI

    OpenAIRE

    Qi, Yanpeng; Shi, Wujun; Naumov, Pavel G.; Kumar, Nitesh; Sankar, Raman; Schnelle, Walter; Shekhar, Chandra; Chou, F. C.; Felser, Claudia; Yan, Binghai; Medvedev, Sergey A.

    2016-01-01

    A pressure-induced topological quantum phase transition has been theoretically predicted for the semiconductor BiTeI with giant Rashba spin splitting. In this work, the evolution of the electrical transport properties in BiTeI and BiTeBr is investigated under high pressure. The pressure-dependent resistivity in a wide temperature range passes through a minimum at around 3 GPa, indicating the predicted transition in BiTeI. Superconductivity is observed in both BiTeI and BiTeBr while the resist...

  17. Superconductivity and magnetism in intermetallic Bi3Ni1-xFex superconductor

    Science.gov (United States)

    Gonsalves, Silvio Henrique; Opata, Yuri Aparecido; Pinheiro, Lincoln Brum Leite Gusmão; Da Silva Leal, Adriane Consuelo; Monteiro, João Frederico Haas Leandro; Siqueira, Ezequiel Costa; de Andrade, André Vitor Chaves; Jurelo, Alcione Roberto

    2016-09-01

    In this work, we investigated the apparent coexistence of superconductivity and magnetism in polycrystalline Bi3Ni1-xFex samples for low concentrations of iron (0 ≤ x ≤ 0.10). The compound was synthesized by the solid-state reaction method and characterized by X-ray diffraction and magnetic measurements. From X-ray, it was observed that the main phase corresponds to an orthorhombic structure with space group Pnma and shows no dependence on the Fe concentration. From magnetic measurements, it was observed that the critical temperature was not affected by iron doping and that ferromagnetism and superconductivity coexist apparently in an interesting interplay.

  18. Tuning the electronic and the crystalline structure of LaBi by pressure: From extreme magnetoresistance to superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Tafti, F. F.; Torikachvili, M. S.; Stillwell, R. L.; Baer, B.; Stavrou, E.; Weir, S. T.; Vohra, Y. K.; Yang, H. -Y.; McDonnell, E. F.; Kushwaha, S. K.; Gibson, Q. D.; Cava, R. J.; Jeffries, J. R.

    2017-01-01

    Extreme magnetoresistance (XMR) in topological semimetals is a recent discovery which attracts attention due to its robust appearance in a growing number of materials. To search for a relation between XMR and superconductivity, we study the effect of pressure on LaBi. By increasing pressure, we observe the disappearance of XMR followed by the appearance of superconductivity at P ≈ 3.5 GPa. We find a region of coexistence between superconductivity and XMR in LaBi in contrast to other superconducting XMR materials. The suppression of XMR is correlated with increasing zero-field resistance instead of decreasing in-field resistance. At higher pressures, P ≈ 11 GPa, we find a structural transition from the face-centered cubic lattice to a primitive tetragonal lattice, in agreement with theoretical predictions. The relationship between extreme magnetoresistance, superconductivity, and structural transition in LaBi is discussed.

  19. Crystalline instability of Bi-2212 superconducting whiskers near room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Cagliero, Stefano; Khan, Mohammad Mizanur Rahman [Torino Universita, ' NIS' Centre of Excellence, Dip. Chimica Generale e Chimica Organica, and CNISM UdR, Turin (Italy); Torino Universita, ' NIS' Centre of Excellence, Dip. Fisica Sperimentale, and CNISM UdR, Turin (Italy); Agostino, Angelo [Torino Universita, ' NIS' Centre of Excellence, Dip. Chimica Generale e Chimica Organica, and CNISM UdR, Turin (Italy); Truccato, Marco [Torino Universita, ' NIS' Centre of Excellence, Dip. Fisica Sperimentale, and CNISM UdR, Turin (Italy); Orsini, Francesco; Marinone, Massimo; Poletti, Giulio [Universita degli Studi di Milano, Istituto di Fisiologia Generale e Chimica Biologica, Milan (Italy); CNR-INFM-S3 NRC, Modena (Italy); Lascialfari, Alessandro [Universita degli Studi di Milano, Istituto di Fisiologia Generale e Chimica Biologica, Milan (Italy); CNR-INFM-S3 NRC, Modena (Italy); Universita degli Studi di Pavia, INFM-CNR c/o Dipartimento di Fisica A. Volta, Pavia (Italy)

    2009-05-15

    We report new evidences for the thermodynamic instability of whisker crystals in the Bi-Sr-Ca-Cu-O (BSCCO) system. Annealing treatments at 90 C have been performed on two sets of samples, which were monitored by means of X-rays diffraction (XRD) and atomic force microscopy (AFM) measurements, respectively. Two main crystalline domains of Bi{sub 2}Sr{sub 2}CuCa{sub 2}O{sub 8+x} (Bi-2212) were identified in the samples by the XRD data, which underwent an evident crystalline segregation after about 60 hours. Very fast dynamics of the surface modifications was also described by the AFM monitoring. Two typologies of surface structures formed after about 3 annealing hours: continuous arrays of dome shaped bodies were observed along the edges of the whiskers, while in the central regions a dense texture of flat bodies was found. These modifications are described in terms of the formation of simple oxide clusters involving a degradation of the internal layers. (orig.)

  20. Structural and Ferroic Properties of La, Nd, and Dy Doped BiFeO3 Ceramics

    Directory of Open Access Journals (Sweden)

    Ashwini Kumar

    2015-01-01

    Full Text Available Polycrystalline samples of Bi0.8RE0.2FeO3 (RE = La, Nd, and Dy have been synthesized by solid-state reaction route. X-ray diffraction (XRD patterns of Bi0.8La0.2FeO3 and Bi0.8Nd0.2FeO3 were indexed in rhombohedral (R3c and triclinic (P1 structure, respectively. Rietveld refined XRD pattern of Bi0.8Dy0.2FeO3 confirms the biphasic (Pnma + R3c space groups nature. Raman spectroscopy reveals the change in BiFeO3 mode positions and supplements structural change with RE ion substitution. Ferroelectric and ferromagnetic loops have been observed in the Bi0.8RE0.2FeO3 ceramics at room temperature, indicating that ferroelectric and ferromagnetic ordering coexist in the ceramics at room temperature. The magnetic measurements at room temperature indicate that rare-earth substitution induces ferromagnetism and discerns large and nonzero remnant magnetization as compared to pristine BiFeO3.

  1. Pressure-enhanced superconductivity in Eu3Bi2S4F4

    Science.gov (United States)

    Luo, Yongkang; Zhai, Hui-Fei; Zhang, Pan; Xu, Zhu-An; Cao, Guang-Han; Thompson, J. D.

    2014-12-01

    The pressure effect on the newly discovered charge-transferred BiS2-based superconductor, Eu3Bi2S4F4 , with a Tc of 1.5 K at ambient pressure, is investigated by transport and magnetic measurements. Accompanied with the enhancement of metallicity under pressures, the onset superconducting transition temperature increases abruptly around 1.0 GPa, reaching ˜10.0 K at 2.26 GPa. Alternating current magnetic susceptibility measurements indicate that a new superconducting phase with a higher Tc emerges and dominates at high pressures. In the broad pressure window of 0.68 GPa≤p ≤2.00 GPa, the high-Tc phase coexists with the low-Tc phase. Hall effect measurements reveal a significant difference in electronic structures between the two superconducting phases. Our work devotes the effort to establish the commonality of pressure effect on the BiS2-based superconductors, and also uncovers the importance of electron carrier density in the high-Tc phase.

  2. Robust polarization and strain behavior of Sm-modified BiFeO3 piezoelectric ceramics.

    Science.gov (United States)

    Walker, Julian; Budic, Bojan; Bryant, Peter; Kurusingal, Valsala; Sorrell, Charles C; Bencan, Andreja; Rojac, Tadej; Valanoor, Nagarajan

    2015-01-01

    The route to phase-pure BiFeO3 (BFO) ceramics with excellent ferroelectric and electromechanical properties is severely impeded by difficulties associated with the perovskite phase stability during synthesis. This has meant that dopants and solid solutions with BFO have been investigated as a means of not only improving the functional properties, but also of improving the perovskite phase formation of BFO-based ceramics. The present work focuses on Sm-modified BFO ceramics of composition Bi0.88Sm0.12FeO3. The polarization and strain behaviors were investigated as a function of the phase composition, microstructure, and chemical composition. Addition of Sm reduces the susceptibility of the BFO perovskite to phase degradation by Si impurities. Si was observed to react into Sm-rich grains dispersed within the microstructure, with no large increases in the amount of bismuth-parasitic phases, namely Bi25FeO39 and Bi2Fe4O9. These as-prepared ceramics exhibited robust polarization behavior showing maximum remnant polarizations of ~40 to 50 μC/cm(2). The electric-fieldinduced strain showed an appreciable stability in terms of the driving field frequency with maximum peak-to-peak strains of ~0.3% and a coercive field of ~130 kV/cm.

  3. Interfacial superconductivity in a bi-collinear antiferromagnetically ordered FeTe monolayer on a topological insulator

    DEFF Research Database (Denmark)

    Manna, S; Kamlapure, A; Cornils, L;

    2017-01-01

    on bulk topological insulators. Surprisingly, we find an energy gap at the Fermi level, indicating superconducting correlations up to Tc∼6 K for one unit cell FeTe grown on Bi2Te3, in contrast to the non-superconducting bulk FeTe. The gap spatially coexists with bi-collinear AFM order. This finding opens...... perspectives for theoretical studies of competing orders in Fe-based superconductors and for experimental investigations of exotic phases in superconducting layers on topological insulators....

  4. Observation of room temperature saturated ferroelectric polarization in Dy substituted BiFeO3 ceramics

    KAUST Repository

    Zhang, Shuxia

    2012-04-06

    High quality Bi1− x Dy x FeO3 (0 ≤ x ≤ 0.15) ceramics have been fabricated by sintering Dy-doped BiFeO3 (BFO) precursor powders at a low temperature of 780 °C. The magnetic properties of BFO were improved by the introduction of Dy on the Bi-site. More importantly, well saturated ferroelectric hysteresis loops and polarization switching currents have been observed at room temperature. A large remnant polarization (2P r) value of 62 μC/cm2 is achieved, which is the highest value reported so far for rare-earth-doped BFO ceramics. Moreover, mechanisms for improved multiferroic properties depending on chemical doping-caused structure evolutions have also been discussed.

  5. Robust two-dimensional superconductivity and vortex system in Bi2Te3/FeTe heterostructures.

    Science.gov (United States)

    Liu, Hong-Chao; Li, Hui; He, Qing Lin; Sou, Iam Keong; Goh, Swee K; Wang, Jiannong

    2016-05-17

    The discovery of two-dimensional superconductivity in Bi2Te3/FeTe heterostructures provides a new platform for the search of Majorana fermions in condensed matter systems. Since Majorana fermions are expected to reside at the core of the vortices, a close examination of the vortex dynamics in superconducting interface is of paramount importance. Here, we report the robustness of the interfacial superconductivity and 2D vortex dynamics in four as-grown and aged Bi2Te3/FeTe heterostructure with different Bi2Te3 epilayer thickness (3, 5, 7, 14 nm). After two years' air exposure, superconductivity remains robust even when the thickness of Bi2Te3 epilayer is down to 3 nm. Meanwhile, a new feature at ~13 K is induced in the aged samples, and the high field studies reveal its relevance to superconductivity. The resistance of all as-grown and aged heterostructures, just below the superconducting transition temperature follows the Arrhenius relation, indicating the thermally activated flux flow behavior at the interface of Bi2Te3 and FeTe. Moreover, the activation energy exhibits a logarithmic dependence on the magnetic field, providing a compelling evidence for the 2D vortex dynamics in this novel system. The weak disorder associated with aging-induced Te vacancies is possibly responsible for these observed phenomena.

  6. The New Superconductor tP-SrPd2Bi2: Structural Polymorphism and Superconductivity in Intermetallics.

    Science.gov (United States)

    Xie, Weiwei; Seibel, Elizabeth M; Cava, Robert J

    2016-04-01

    We consider a system where structural polymorphism suggests the possible existence of superconductivity through the implied structural instability. SrPd2Bi2 has two polymorphs, which can be controlled by the synthesis temperature: a tetragonal form (CaBe2Ge2-type) and a monoclinic form (BaAu2Sb2-type). Although the crystallographic difference between the two forms may, at first, seem trivial, we show that tetragonal SrPd2Bi2 is superconducting at 2.0 K, whereas monoclinic SrPd2Bi2 is not. We rationalize this finding and place it in context with other 1-2-2 phases.

  7. Superconductivity in Hg-Substituted BaPb0.75Bi0.25O3

    Institute of Scientific and Technical Information of China (English)

    Yong-Liang Chen; Ya-Jing Cui; Yong Zhang; Cui-Hua Cheng; Yong Zhao

    2008-01-01

    A series of Hg-doped BaPb0.75Bi0.25O3 with a nominal composition of BaPb0.75-xHgxBi0.25O3 (x=0 to 0.40 with 0.05 intervals) have been synthesized by solid-state reaction. These compounds exhibit a cubic perovskite-related structure with the lattice parameter being expanded by Hg doping. Superconducting transition temperature Tc and superconducting volume fraction are suppressed by Hg doping in the low doping level region (0≤ x ≤0.25). However, further increasing Hg content makes the superconductivity recovered at x>0.3. The superconductivity suppression in Hg-doped BaPb0.75Bi0.25O3 can be explained by the decrease of electron carrier concentration as well as the band- narrowing-induced electron localization.

  8. Topological Quantum Phase Transition and Superconductivity Induced by Pressure in the Bismuth Tellurohalide BiTeI.

    Science.gov (United States)

    Qi, Yanpeng; Shi, Wujun; Naumov, Pavel G; Kumar, Nitesh; Sankar, Raman; Schnelle, Walter; Shekhar, Chandra; Chou, Fang-Cheng; Felser, Claudia; Yan, Binghai; Medvedev, Sergey A

    2017-03-06

    A pressure-induced topological quantum phase transition has been theoretically predicted for the semiconductor bismuth tellurohalide BiTeI with giant Rashba spin splitting. In this work, evolution of the electrical transport properties in BiTeI and BiTeBr is investigated under high pressure. The pressure-dependent resistivity in a wide temperature range passes through a minimum at around 3 GPa, indicating the predicted topological quantum phase transition in BiTeI. Superconductivity is observed in both BiTeI and BiTeBr, while resistivity at higher temperatures still exhibits semiconducting behavior. Theoretical calculations suggest that superconductivity may develop from the multivalley semiconductor phase. The superconducting transition temperature, Tc , increases with applied pressure and reaches a maximum value of 5.2 K at 23.5 GPa for BiTeI (4.8 K at 31.7 GPa for BiTeBr), followed by a slow decrease. The results demonstrate that BiTeX (X = I, Br) compounds with nontrivial topology of electronic states display new ground states upon compression.

  9. Superconductive transition and the intergrain effects of mixture ceramic systems synthesized using Citrate pyrolysis precursor method

    Energy Technology Data Exchange (ETDEWEB)

    Hagiwara, M; Kitada, R; Shima, T; Nishio, K [Department of Electronics, Kyoto Institute of Technology, Kyoto, 606-8585 (Japan); Deguchi, H [Faculty of Engineering, Kyushu Institute of Tecnnology, Kitakyushu 804-8550 (Japan); Koyama, K [Faculty of Integrated Arts and Sciences, University of Tokushima, Tokushima 770-8502 (Japan); Matsuura, M, E-mail: hag@kit.ac.j [Fukui University of Technology, Fukui 910-8505 (Japan)

    2009-03-01

    Superconductive characteristics of Pr{sub 2}Ba{sub 4}Cu{sub 7}O{sub 15-delta} (Pr247) ceramics with crystalline phase inhomogeneity for the stacking structures is examined experimentally, using reference observations for multi-phased ceramic sample consists simply of PrBa{sub 2}Cu{sub 4}O{sub 8} (Pr124) and PrBa{sub 2}Cu{sub 3}O{sub 7-delta} (Pr123). After reduction treatment by vacuum-heating, the reference multiphased sample shows onset of abrupt electric resistivity dropping and also weak Meissner magnetization below approx20 K. The results suggest that superconductivity at CuO double chains in Pr124 grains is caused by charge transfer from neighbouring Pr123 grains. Such a charge transfer effect is thought to occur also in Pr247 sample including phase inhomogeneity.

  10. Fluorinated precursors of superconducting ceramics, and methods of making the same

    Science.gov (United States)

    Wiesmann, Harold; Solovyov, Vyacheslav

    2008-04-22

    This invention provides a method of making a fluorinated precursor of a superconducting ceramic. The method comprises providing a solution comprising a rare earth salt, an alkaline earth metal salt and a copper salt; spraying the solution onto a substrate to provide a film-covered substrate; and heating the film-covered substrate in an atmosphere containing fluorinated gas to provide the fluorinated precursor.

  11. Applying experimental constraints to a one-dimensional model for BiS2 superconductivity

    Science.gov (United States)

    Griffith, M. A.; Foyevtsova, K.; Continentino, M. A.; Martins, G. B.

    2016-10-01

    Recent ARPES measurements [Sugimoto et al., Phys. Rev. B 92 (2015) 041113] have confirmed the one-dimensional character of the electronic structure of CeO0.5 F0.5 BiS2, a representative of BiS2-based superconductors. In addition, several members of this family present sizable increase in the superconducting transition temperature Tc under application of hydrostatic pressure. Motivated by these two results, we propose an effective one-dimensional three-orbital model, whose kinetic energy part, obtained through ab initio calculations, is supplemented by pair-scattering terms, which are treated at the mean-field level. We solve the gap equations self-consistently and then systematically probe which combination of pair-scattering terms gives results consistent with experiment, namely, a superconducting dome with a maximum Tc at the right chemical potential and a sizable increase in Tc when the magnitude of the hoppings is increased. For these constraints to be satisfied multi-gap superconductivity is required, in agreement with experiments, and one of the hoppings has a dominant influence over the increase of Tc with pressure.

  12. Influence of preparation conditions on superconducting properties of Bi-2223 thin films

    Indian Academy of Sciences (India)

    N T Mua; A Sundaresan; N K Man; D D Dung

    2014-02-01

    We report electrical transport properties of Bi2Sr2Ca2Cu3O10+ (Bi-2223) superconducting thin films fabricated by pulsed-laser deposition on SrTiO3 substrate. The aim of the study was to investigate the influence of preparation conditions such as deposition temperature (S), annealing time (A) and deposition rate (). A critical temperature (c) as high as 110 K and critical current density (c) of 6.2 × 106 A/cm2 at 20 K were obtained for S = 760° C, A = 4h and = 1.5 Å/s. We also investigated the effect of Li doping on Bi-2223 thin films. Li intercalation results in high resistive onset transition temperature and the resistivity shows broadening in magnetic field that increases with field. The large broadening of resistivity curve in magnetic field suggests that this phenomenon is directly related to the intrinsic superconducting properties of the copper oxide superconductors. The sudden drop in c at relatively low magnetic field ( < 0.5 tesla) is due to the effect of Josephson weak-links at the grain boundaries.

  13. Hysteresis in the I{sub c}(H) characteristics of high-temperature superconducting ceramics and thin films

    Energy Technology Data Exchange (ETDEWEB)

    Altshuler, E.; Musa, J.; Hart, C.; Ares, O. [Univ. of Havana, La Habana (Cuba)] [and others

    1995-12-01

    The experimental hysteretic behavior of the transport critical current observed in ceramic Y-Ba-Cu-O and (Bi-Pb)-Sr-Ca-Cu-O, as well as thin film Y-Ba-Cu-O, are presented. The data are analyzed semiqualitatively. The results show certain similarities among the ceramic samples and the films.

  14. Piezoelectric response of BiFeO3 ceramics at elevated temperatures

    Science.gov (United States)

    Rojac, Tadej; Makarovic, Maja; Walker, Julian; Ursic, Hana; Damjanovic, Dragan; Kos, Tomaz

    2016-07-01

    The high Curie temperature (TC ˜ 825 °C) of BiFeO3 has made this material potentially attractive for the development of high-TC piezoelectric ceramics. Despite significant advances in the search of new BiFeO3-based compositions, the piezoelectric behavior of the parent BiFeO3 at elevated temperatures remains unexplored. We present here a systematic analysis of the converse, longitudinal piezoelectric response of BiFeO3 measured in situ as a function of temperature (25-260 °C), driving-field frequency, and amplitude. Earlier studies performed at room temperature revealed that the frequency and field dependence of the longitudinal response of BiFeO3 is dominated by linear and nonlinear piezoelectric Maxwell-Wagner mechanisms, originating from the presence of local conductive paths along domain walls and grain boundaries within the polycrystalline matrix. This study shows that the same mechanisms are responsible for the distinct temperature dependence of the piezoelectric coefficient and phase angle and thus identifies the local electrical conductivity as the key for controlling the temperature dependent piezoelectric response of BiFeO3 and possibly other, more complex BiFeO3-based compositions.

  15. Dielectric Properties and Defect Structure of Bi-doped SrTiO3 Ceramics

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The dielectric properties of ceramics with composition of (Sr1-xBix)TiO3+x/2(where x=0.05~0.70 ) were measured at frequency of 1 MHz. The experimental results indicate that the dielectric properties of (Sr1-xBix)TiO3+x/2 system are greatly varied with an increase of the stoichiometric amounts of Bi2O3. The relative permittivity of the solid solutions is high, and the dissipation factor is low. The positron annihilation technique(PAT) was adopted to study the defect structure. An explanation of the dielectric properties of Bi-doped SrTiO3 ceramics has been suggested in terms of electron-compensation and vacancy or defect-compensation mechanisms and space-charge polarization mechanism.

  16. Synthesis and optical properties of Pr and Ti doped BiFeO3 ceramics

    Science.gov (United States)

    Singh, Vikash; Sharma, Subhash; Dwivedi, R. K.

    2016-05-01

    Bi1-xPrxFe1-xTixO3 ceramics with x = 0.00, 0.10 and 0.20 were synthesized by solid state reaction method. Rietveld fitting of diffraction data reveals structural transition from rhombohedral phase (R3C) for x ≤ 0.10 to orthorhombic phase (Pnma) for x = 0.20. FTIR spectra exhibit broad absorption bands, which may be due to the overlapping of Fe-O and Bi-O vibrations in these ceramics. UV-visible spectroscopy results show strong absorption of light in the spectral range of 400-600 nm, indicating optical band gap in the visible region for these samples.

  17. Superconducting gap in Bi-Sr-Ca-Cu-O by high-resolution angle-resolved photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Olson, C.G.; Liu, R.; Yang, A.B.; Lynch, D.W. (Iowa State Univ., Ames (USA)); Arko, A.J.; List, R.S. (Los Alamos National Lab., NM (USA)); Veal, B.W.; Chang, Y.C.; Jiang, P.Z.; Paulikas, A.P. (Argonne National Lab., IL (USA))

    1989-08-18

    Detailed studies indicate a superconducting gap in the high-temperature superconductor Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}. Photoemission measurements with high energy and angle resolution isolate the behavior of a single band as it crosses the Fermi level in both the normal and superconducting states, giving support to the Fermi liquid picture. The magnitude of the gap is 24 millielectron volts. 18 refs., 3 figs.

  18. Dopant rearrangement and superconductivity in Bi2Sr2-xLaxCuO6 thin films under annealing

    Science.gov (United States)

    Cancellieri, C.; Lin, P. H.; Ariosa, D.; Pavuna, D.

    2007-06-01

    By combining x-ray diffraction (XRD), x-ray photoemission spectroscopy (XPS) and AC susceptibility measurements we investigate the evolution of structural and superconducting properties of La-doped Bi-2201 thin films grown by pulsed laser deposition (PLD) under different annealing conditions. We find that the main effect of oxygen annealing is to improve the crystal coherence by enabling La cation migration to the Sr sites. This activates the desired hole doping. Short-time Ar annealing removes the interstitial oxygen between the BiO layers, fine adjusting the effective hole doping. The superconducting critical temperature is consequently enhanced. However, longer annealings result in phase separation and segregation of the homologous compound Bi-1201. We attribute this effect to the loss of Bi during the annealing.

  19. Dopant rearrangement and superconductivity in Bi(2)Sr(2-x)La(x)CuO(6) thin films under annealing.

    Science.gov (United States)

    Cancellieri, C; Lin, P H; Ariosa, D; Pavuna, D

    2007-06-20

    By combining x-ray diffraction (XRD), x-ray photoemission spectroscopy (XPS) and AC susceptibility measurements we investigate the evolution of structural and superconducting properties of La-doped Bi-2201 thin films grown by pulsed laser deposition (PLD) under different annealing conditions. We find that the main effect of oxygen annealing is to improve the crystal coherence by enabling La cation migration to the Sr sites. This activates the desired hole doping. Short-time Ar annealing removes the interstitial oxygen between the BiO layers, fine adjusting the effective hole doping. The superconducting critical temperature is consequently enhanced. However, longer annealings result in phase separation and segregation of the homologous compound Bi-1201. We attribute this effect to the loss of Bi during the annealing.

  20. Two-dimensional superconductivity at the interface of a Bi2Te3/FeTe heterostructure.

    Science.gov (United States)

    He, Qing Lin; Liu, Hongchao; He, Mingquan; Lai, Ying Hoi; He, Hongtao; Wang, Gan; Law, Kam Tuen; Lortz, Rolf; Wang, Jiannong; Sou, Iam Keong

    2014-06-23

    The realization of superconductivity at the interface between a topological insulator and an iron-chalcogenide compound is highly attractive for exploring several recent theoretical predictions involving these two new classes of materials. Here we report transport measurements on a Bi2Te3/FeTe heterostructure fabricated via van der Waals epitaxy, which demonstrate superconductivity at the interface, which is induced by the Bi2Te3 epilayer with thickness even down to one quintuple layer, though there is no clear-cut evidence that the observed superconductivity is induced by the topological surface states. The two-dimensional nature of the observed superconductivity with the highest transition temperature around 12 K was verified by the existence of a Berezinsky-Kosterlitz-Thouless transition and the diverging ratio of in-plane to out-plane upper critical field on approaching the superconducting transition temperature. With the combination of interface superconductivity and Dirac surface states of Bi2Te3, the heterostructure studied in this work provides a novel platform for realizing Majorana fermions.

  1. Introduction of artificial pinning centre in {open_quotes}Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}{close_quotes} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Majewski, P.; Aldinger, F. [Max-Planck-Institut fuer Metallforschung, Stuttgart (Germany); Elschner, S. [Hoechst AG, Frankfurt am Main (Germany)] [and others

    1994-12-31

    Considering the phase equilibrium diagram of the system Bi{sub 2}O{sub 3}-SrO-CaO-CuO, single phase {open_quotes}Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}{close_quotes} ceramics have been transformed by a simple annealing procedure into multi phase samples. The transformation results in the formation of second phases and in an increase of the intra grain critical current density at 1 T of five times. This increase is believed to express improved pinning properties of the superconducting crystals. The prepared pinning centres are believed to be e.g. coherent precipitates (Guinier-Preston-zones) within the superconducting crystals.

  2. Theory analysis of critical-current degeneration in bended superconducting tapes of multifilament composite Bi2223/Ag

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Peifeng; Wang, Xingzhe, E-mail: xzwang@lzu.edu.cn

    2015-10-15

    Highlights: • We proposed an empirical model to describe carrying-current degradation of bent Bi2223/Ag tapes. • Asymmetric damage of superconductor multifilament is taken into account. • Both the loading and unloading processes of bend deformation are captured. • Carrying-current property can be improved by designing configuration of the multifilament core. - Abstract: This paper proposed a degradation model to explore the influence of the mechanical bending deformation on the critical-current of superconducting composite Bi2223/Ag tape taking into account the asymmetric mechanical damage. With the aid of Weibull distribution function of statistical damage of filaments, the critical-current dependence upon bending strain of the superconducting tape in processes of loading and unloading is characterized. The degradation profile of critical-current in the superconducting composite tape is theoretically investigated by the proposed model for different critical damage strains and configurations of superconducting multifilament core at the cross-section. It is shown that the theoretical predictions are in reasonably good agreement with the experimental data, and the configuration of the multifilament core of the superconducting composite tape has a significant influence on the critical-current degradation. The superconducting multifilament core located near the compression region of the cross-section remarkably improves the mechanical and carrying-current capabilities of the superconducting composite tape.

  3. NUMERICAL SIMULATION OF MECHANICAL BEHAVIORS OF SUPERCONDUCTING POWDER BSCCO (BiSrCaCuO)

    Institute of Scientific and Technical Information of China (English)

    ZHAO Yinghong; LEI Liping; ZENG Pan

    2007-01-01

    An equivalent continuum method and a deformable discrete method to describe the mechanical behaviors of superconducting powder BSCCO (BiSrCaCuO) aggregate are studied systematically. The equivalent continuum model idealizes the aggregation of the powder as an equivalent continuum material. The powder aggregate yielding is caused by not only the deviatoric stress but also the hydrostatic stress and the modified Drucker-Prager/Cap model is adopted to describe the mechanical behaviors of BSCCO powder aggregate in continuum method. The deformable discrete model is known as a direct model, which considers the discrete nature of the powder particles. Its framework encompasses the local behaviors between the particles, such as particles contact, sliding and rolling. Based on commercial finite element software ABAQUS, the equivalent continuum model and the deformable discrete model are used to simulate the confined compression of superconducting powder BSCCO, and the numerical results show agreement with experimental results, which verify the correctness of these built models. Compared with the equivalent continuum model based on macroscopic statistics method, the deformable discrete model can present the microscopic information during processing and can describe the nature of mechanical behaviors of superconducting powder BSCCO. But from an industrial viewpoint, the equivalent continuum model has a definitive edge over the microscopic models in that the gross behavior of the powder mass can be modeled and simulated on an industrial scale.

  4. Microstructure and relaxor ferroelectric properties of Bi{sub 2}O{sub 3}-doped strontium barium niobate ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jinglei, E-mail: lilei19871003@yahoo.com.cn; Pu, Yongping; Wang, Zhuo; Dong, Zijing; Dai, Jie

    2013-11-01

    Highlights: • Bi{sub 2}O{sub 3} addition could promote the grain growth in Sr{sub 0.4}Ba{sub 0.6}Nb{sub 2}O{sub 6} ceramics. • Doping Bi{sub 2}O{sub 3} could improve the dielectric constant and lower the dielectric loss. • The dielectric characteristics of doping Bi{sub 2}O{sub 3} samples showed relaxation behavior. • The P–E hysteresis loops for doping Bi{sub 2}O{sub 3} ceramics became slimmer. -- Abstract: (1 − x) Sr{sub 0.4}Ba{sub 0.6}Nb{sub 2}O{sub 6}–xBi{sub 2}O{sub 3} (0.00 ≤ x ≤ 0.20) ceramics were prepared by conventional solid-state reaction method. The microstructure, dielectric properties and P–E hysteresis loops of ceramics were investigated via X-ray diffraction, scanning electron microscope (SEM), Agilent E4980A and modified Sawyer–Tower circuit, respectively. XRD results showed the obtained ceramics were of tungsten bronze structure, and second phase Sr{sub 0.4}Ba{sub 0.6}Bi{sub 2}Nb{sub 2}O{sub 9} was detected at high doping concentration. SEM results showed suitable Bi{sub 2}O{sub 3} addition could reduce the sintering temperature and assist the grain growth. The dielectric characteristics exhibited diffuse phase transition phenomena, which were verified by linear fitting of the modified Curie–Weiss law. Besides, the relaxor ferroelectric properties of ceramics followed the Vogel–Fulcher relationship well. The P–E hysteresis loops became slimmer with increasing the Bi{sub 2}O{sub 3} addition, leading to a gradually decrease in both remnant polarization (P{sub r}) and coercive field (E{sub c})

  5. Superconductivity in Bi–Pb–Sr–Ca–Cu–O ceramics with YBCO as additive

    Energy Technology Data Exchange (ETDEWEB)

    Arlina, A., E-mail: arlina85@gmail.com [Superconductivity and Thin Film Laboratory, Department of Physics, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Faculty of Earth Science, Universiti Malaysia Kelantan, Jeli Campus, Locked Bag No. 100, 17600 Jeli, Kelantan (Malaysia); Halim, S.A. [Superconductivity and Thin Film Laboratory, Department of Physics, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Institute for Advanced Technology (ITMA), Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Kechik, M.M. Awang; Chen, S.K. [Superconductivity and Thin Film Laboratory, Department of Physics, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia)

    2015-10-05

    Highlights: • Effect of YBCO addition on the superconductivity in Bi{sub 1.6}Pb{sub 0.4}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub δ}. • The highest resistivity measurement was observed for the samples with x = 0.02 wt.% of YBCO at 102 K. • The crystal structure remains in orthorhombic where the lattice parameter is a ≠ b ≠ c for these samples. • Generally, all samples displayed a thin flakey plate like grains with random distribution. • The inter-grain peaks due to ac losses shifted to lower temperatures when YBCO addition increases. - Abstract: The effect of YBCO addition on the superconductivity in Bi{sub 1.6}Pb{sub 0.4}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub δ} (BSCCO) systems was studied. The samples were prepared through solid state reaction and the properties have been investigated via resistivity measurement (R–T), Scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis. The highest resistivity measurement was observed for the samples with x = 0.02 of YBCO at 102 K. Generally, all samples exhibit metallic behavior above transition temperature T{sub C} onset. From the XRD data, it is observed that the volume percentage of the Bi-2223 phase is initially 75% for the pure samples but decreases till 25% with the increasing Bi-2212 phase. Analysis of the temperature dependence of the AC susceptibility near the transition temperature has been done. The field effect on AC susceptibility was measured. The field increased from 0.05 Oe to 2.00 Oe and the peak temperature (T{sub P}) gradually decreased to lower temperature from 107.0 K to 108.5 K.

  6. Characterization and thermophysical properties of bi-based ceramic superconductors. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Gamble, Brian K. [Clemson Univ., Clemson, SC (United States)

    2001-05-31

    The BES supported research at Clemson University and South Carolina State University (1994-1999) on the BiSCCO high temperature superconductors, as well as other research at Clemson and elsewhere on a range of conducting and superconducting materials, revealed substantial evidence that dimensionality plays a key role in their magnetic and transport properties. Previous theoretical and experimental activities have shown that high magnetic fields can have novel and large effects on the ground state of low dimensional systems. Much new physics is expected to result from these interactions, not only the suppression or restoration of superconductivity, but also the enhancement (or even field induced) charge density wave nesting and the destruction of density wave states.

  7. Effects of intergrain and intragrain currents on flux profile in granular superconducting ceramics

    Science.gov (United States)

    Godelaine, P. A.; Ausloos, M.

    1990-11-01

    We present generalizations of Bean critical state model to take into account granular effects as in high critical temperature superconductor ceramics. Both intragrain and intergrain critical current effect are discussed as they modify the "flux profile" determined by AC susceptibility measurements. We also examine the effect of Josephson weak links on the flux profile. We show how to obtain these electrical currents from the data together with the "granular fraction" and the flux penetration depth. Data on Bi 0.85Pb 0.15SrCa 1.2Cu 2O 6 sample is shown to be fitted to our theoretical expressions.

  8. Robust antiferromagnetism preventing superconductivity in pressurized (Ba 0.61 K 0.39)Mn2Bi2.

    Science.gov (United States)

    Gu, Dachun; Dai, Xia; Le, Congcong; Sun, Liling; Wu, Qi; Saparov, Bayrammurad; Guo, Jing; Gao, Peiwen; Zhang, Shan; Zhou, Yazhou; Zhang, Chao; Jin, Shifeng; Xiong, Lun; Li, Rui; Li, Yanchun; Li, Xiaodong; Liu, Jing; Sefat, Athena S; Hu, Jiangping; Zhao, Zhongxian

    2014-12-05

    BaMn2Bi2 possesses an iso-structure of iron pnictide superconductors and similar antiferromagnetic (AFM) ground state to that of cuprates, therefore, it receives much more attention on its properties and is expected to be the parent compound of a new family of superconductors. When doped with potassium (K), BaMn2Bi2 undergoes a transition from an AFM insulator to an AFM metal. Consequently, it is of great interest to suppress the AFM order in the K-doped BaMn2Bi2 with the aim of exploring the potential superconductivity. Here, we report that external pressure up to 35.6 GPa cannot suppress the AFM order in the K-doped BaMn2Bi2 to develop superconductivity in the temperature range of 300 K-1.5 K, but induces a tetragonal (T) to an orthorhombic (OR) phase transition at ~20 GPa. Theoretical calculations for the T and OR phases, on basis of our high-pressure XRD data, indicate that the AFM order is robust in the pressurized Ba0.61K0.39Mn2Bi2. Both of our experimental and theoretical results suggest that the robust AFM order essentially prevents the emergence of superconductivity.

  9. Interfacial superconductivity in a bi-collinear antiferromagnetically ordered FeTe monolayer on a topological insulator

    Science.gov (United States)

    Manna, S.; Kamlapure, A.; Cornils, L.; Hänke, T.; Hedegaard, E. M. J.; Bremholm, M.; Iversen, B. B.; Hofmann, Ph.; Wiebe, J.; Wiesendanger, R.

    2017-01-01

    The discovery of high-temperature superconductivity in Fe-based compounds triggered numerous investigations on the interplay between superconductivity and magnetism, and on the enhancement of transition temperatures through interface effects. It is widely believed that the emergence of optimal superconductivity is intimately linked to the suppression of long-range antiferromagnetic (AFM) order, although the exact microscopic picture remains elusive because of the lack of atomically resolved data. Here we present spin-polarized scanning tunnelling spectroscopy of ultrathin FeTe1-xSex (x=0, 0.5) films on bulk topological insulators. Surprisingly, we find an energy gap at the Fermi level, indicating superconducting correlations up to Tc~6 K for one unit cell FeTe grown on Bi2Te3, in contrast to the non-superconducting bulk FeTe. The gap spatially coexists with bi-collinear AFM order. This finding opens perspectives for theoretical studies of competing orders in Fe-based superconductors and for experimental investigations of exotic phases in superconducting layers on topological insulators.

  10. Processing and characterization of superconducting solenoids made of Bi-2212/Ag-alloy multifilament round wire for high field magnet applications

    Science.gov (United States)

    Chen, Peng

    -off and full coil reaction. The coil was successfully tested at the NHMFL generating 33.8 T combined magnetic field in a 31.2 T background field. Multiple quenches occurred safely, which also illustrates that the insulation provided sufficient dielectric standoff. For Bi-2212 RW with a typical as-drawn diameter of 1.0-1.5 mm, this 15 microm thick insulation allows a very high coil packing factor of ~0.74, whereas earlier alumino-silicate braid insulation only allows packing factors of 0.38-0.48. In addition to the commercial TiO2/polymer insulation, we have also investigated sol-gel based ceramic coatings through collaboration with Harran University and another TiO2 based insulation coating at the NHMFL. Since Bi-2212 superconducting coils employ the Wind-and-React (W&R) technology, there are some potential issues in processing Bi-2212 coils, in particular for coils with a large thermal mass and dense oxide insulation coating. For this study, several Bi-2212 test solenoids with an outer diameter (OD) of about 90 mm were built and heat treated in 1 bar flowing oxygen with deadweights applied so as to simulate large coil packs. After the heat treatment (HT), coils were epoxy impregnated and cut. Winding pack was checked using SEM in terms of conductor geometry and insulation. Some samples were extracted to measure transport critical current Ic and critical temperature Tc. The results are very promising: test coils presented low creep behavior after standard partial melt HT under mechanical load, and no Ic degradation was found due to the application of mechanical load, and no inadequate oxygenation issue was seen for thick coils with ceramic coating on the wire. However, coils were partially electrically shorted after 1 bar HT under mechanical load, and we believe that increasing insulation coating thickness is necessary. In addition, several small solenoids were manufactured to study OP processing of Bi-2212 coils. The preliminary results indicate that there are some gaps

  11. Nonaqueous slip casting of YBa2Cu3O(7-x) superconductive ceramics. Ph.D. Thesis - 1993

    Science.gov (United States)

    Hooker, Matthew W.; Taylor, Theodore D.

    1994-01-01

    This study investigates the slip casting of YBa2Cu3O(7-x) powders using nonaqueous carrier liquids and fired ceramic molds. The parameters of the process examined here include the rheological properties of YBa2Cu3O(7-x) powder dispersed in various solvent/dispersant systems, the combination of nonaqueous slips with fired ceramic molds to form the superconductive ceramics, the process-property relationships using a four-factor factorial experiment, and the applicability of magnetic fields to align the YBa2Cu3O(7-x) grains during the casting process.

  12. Effect of cooling rate on evolution of superconducting phases during decomposition and recrystallization of (Bi,Pb)-2223 core in Ag-sheathed tape

    Institute of Scientific and Technical Information of China (English)

    LI Jingyong; LI Jianguo; ZHENG Huiling; LI Chengshan; LU Yafeng; ZHOU Lian

    2006-01-01

    The reformation of (Bi,Pb)-2223 from the liquid or melt is very important for a melting process of (Bi,Pb)-2223 tape. By combination of quenching experiment with X-ray diffraction (XRD) analysis, the effect of cooling rate on the evolution of three superconducting phases in the (Bi,Pb)-2223 core of Ag-sheathed tape was investigated. The results show that (Bi,Pb)-2223 reformation from the melt seems to experience different routes during slowly cooling at different rates. One is that (Bi,Pb)-2223 phase reformed directly from the melt, and no Bi-2212 participate in this process. The other is that (Bi,Pb)-2223 is converted from the intermediate product, Bi-2212, which formed from the melt during the first cooling stage. Due to the inherent sluggish formation kinetics of (Bi,Pb)-2223 from Bi-2212, only partial (Bi,Pb)-2223 can finally be reformed with the second route.

  13. The origin of photovoltaic responses in BiFeO3 multiferroic ceramics.

    Science.gov (United States)

    Tu, C-S; Hung, C-M; Schmidt, V H; Chien, R R; Jiang, M-D; Anthoninappen, J

    2012-12-12

    Multiferroic BiFeO(3) (BFO) ceramics with electrodes of indium tin oxide (ITO) and Au thin films exhibit significant photovoltaic effects under near-ultraviolet illumination (λ = 405 nm) and show strong dependences on light wavelength, illumination intensity, and sample thickness. The correlation between photovoltaic responses and illumination intensity can be attributed to photo-excited and thermally generated charge carriers in the interface depletion region between BFO ceramic and ITO thin film. A theoretical model is developed to describe the open-circuit photovoltage and short-circuit photocurrent density as a function of illumination intensity. This model can be applied to the photovoltaic effects in p-n junction type BFO thin films and other systems. The BFO ceramic exhibits stronger photovoltaic responses than the ferroelectric Pb(1-x)La(x)(Zr(y)Ti(1-y))(1-x/4)O(3) (PLZT) ceramics under near-ultraviolet illumination. Comparisons are made with other systems and models for the photovoltaic effect.

  14. Influence of Oxygen Content on the Superconductivity of Bi-Based Oxides Homologous to 2212 Phase

    Science.gov (United States)

    Deshimaru, Yuichi; Otani, Tetsuya; Shimizu, Youichi; Miura, Norio; Yamazoe, Noboru

    1991-10-01

    Thermal desorption of oxygen and its relevance to superconductivity were examined for a series of oxides Bi2Sr2-xCa1+xCu2Oy (x=0, 0.25, 0.5, 0.8 and 1.0) isostructural to the 2212 phase. The total oxygen desorbed up to 600°C amounted to 2˜ 3× 10-5 mol/g for each oxide. Tc was constant at about 80 K for all the as-prepared oxides but Tc decreased linearly with x from 97 K (x=0) to 67 K (x=1.0) for the oxygen-desorbed oxides. The total oxygen contents (y) were determined and correlated with Tc, which increased for x=0 and 0.25, whereas it went through a maximum at about y=8.15 for x=0.8.

  15. Relationship between oxygen content and seebeck coefficient of Bi-based superconducting oxides

    Science.gov (United States)

    Miura, N.; Sakata, F.; Shimizu, Y.; Deshimaru, Y.; Yamazoe, N.

    1994-12-01

    The correlations among Seebeck coefficient, oxygen content and superconducting property were examined for four Bi-based oxides (2223 and 2212 phases). Each oxide underwent reversible sorption and desorption of small amounts of oxygen (ca.3x10 -5mol/g) in the temperature range 100-600 °C. In good agreement with such behavior, the Seebeck coefficient (Q) of each oxide was found to change reversibly with changing temperature, suggesting that Q is a reversible function of oxygen content. It was further found that the highest Tc was reached at the oxygen content at which Q was incidentally brought to be around zero at 100 °C for each oxide.

  16. Relation between oxygen content and superconductivity in Bi-Sr-Ca-Cu-O system

    Energy Technology Data Exchange (ETDEWEB)

    Miura, N.; Deshimaru, Y.; Otani, T.; Shimizu, Y.; Yamazoe, N. (Dept. of Materials Science and Tech., Graduate School of Engineering Sciences, Kyushu Univ., Fukuoka (Japan))

    1991-12-01

    Oxygen sorption-desorption behaviors as well as superconducting properties were examined for a series of 2212-isostructural oxides, Bi{sub 2}Sr{sub 2-x}Ca{sub 1+x}Cu{sub 2}O{sub y} (x=0-1.0). It was found that oxygen sorption and desorption at temperatures below 600deg C brought about reversible shifts of Tc in a manner dependent on x. Quantitative determination of oxygen content (y) revealed that, as y decreased with oxygen desorption from the as-prepared levels, Tc increased montonically for x=0 and 0.25, while it went through a maximum at y=8.15 for x=0.8. (orig.).

  17. Magnetic impurity induced states in superconducting Bi2Sr2CaCuO8+δ

    Science.gov (United States)

    Choubey, Peayush; Kreisel, Andreas; Berlijn, Tom; Andersen, Brian; Hirschfeld, Peter

    2015-03-01

    We revisit the Ni impurity problem in superconducting Bi2Sr2CaCu2O8+δ (BSCCO-2212) using the Bogoliubov- de Gennes (BdG)-Wannier approach. We solve the self-consistent BdG equations on a square lattice and use first principle-based Wannier function to compute the local density of states (LDOS) with sub-atomic resolution in the vicinity of a magnetic impurity. We find two spin-resolved virtual bound states localized around the impurity position. The spatial LDOS patterns at the resonance energies are found to be in excellent agreement with STM experiment, and can be understood by accounting for the tails of Cu Wannier function.

  18. Development of superconducting magnets fabricated with PAIR processed Bi-2212/Ag multilayer tapes; PAIR purosesu Bi-2212/Ag taso senzai wo mochiita chodedo magunetto no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Otani, N.; Koizumi, T.; Hasegawa, T. [Showa Electric Wire and Cable Co., Ltd., Kanagawa (Japan); Kitaguchi, H.; Kumakura, H.; Togano, K. [National Research Inst. for Metals, Tokyo (Japan); Miao, H. [Japan Science and Tech. Corp., Tsukuba (Japan)

    1999-06-07

    Bi2212 oxide superconducting wire rod has large critical current density at 20K or less. It is expected as practical conductors such as high magnetic field insert magnet and refrigerating machine cryogenic magnet. PAIR process, which we developed, introduced spare baking and intermediate preforming into the fabrication process of Bi2212/Ag wire rod. The superconductivity of the multilayer tape wire rod was more and more greatly improved, and it brought it close to the use conductor of the practical magnet. This time, in the coil using this wire rod, in order to examine electromagnetic force countermeasure in the high magnetic field application, the CuAg tape of which tensile strength was often high was used as reinforcing agent, and 2 kinds of double pancake coil were produced thermal conductivity. The coil was energized and was tested in 4.2K, in the external magnetic field. (NEDO)

  19. Lanthanide Doping Effects on Properties of Sr2Bi4 Ti5O18 Ceramics

    Institute of Scientific and Technical Information of China (English)

    Qiang Feng; Zhu Jun; Chen Xiaobing

    2004-01-01

    Ceramic samples of samarium, dysprosium and lanthanum doped Sr2 Bi4Ti5 O18 (SBTi) were prepared by solid-state reaction. The remnant polarization (2Pr) increases at first, then decreases with the increase of doping content.The 2Pr for Sm and Dy doped SBTi reached a maximum value of 18.2μC·cm-2 and 20.1μC·m-2, respectively,when doping content was 0.01. La doped SBTi has maximum 2Pr value of 18.4μC·m-2 with doping content of 0.05. The variation of ferroelectric properties of Sr2Bi4-xLnxTi5O18 (Ln = Sm, Dy and La) should be determined by the competition of the decrease of oxygen vacancy concentration and the relief of structural distortion.

  20. Reinforced magnetic properties of Ni-doped BiFeO3 ceramic

    Science.gov (United States)

    Hwang, J. S.; Yoo, Y. J.; Lee, Y. P.; Kang, J.-H.; Lee, K. H.; Lee, B. W.; Park, S. Y.

    2016-08-01

    Multiferroic materials attract considerable interest because of the wide range of potential applications such as spintronic devices, data storage devices and sensors. As a strong candidate for the applications among the limited list of single-phase multiferroic materials, BiFeO3 (BFO) is a quite attractive material due to its multiferroic properties at room temperature (RT). However, BFO is widely known to have large leakage current and small spontaneous polarization due to the existence of crystalline defects such as oxygen vacancies. Furthermore, the magnetic moment of pure BFO is very weak owing to its antiferromagnetic nature. In this paper, the effects of Ni2+ substitution on the magnetic properties of bulk BFO were investigated. BFO, and BiFe0.99Ni0.01O3, BiFe0.98Ni0.02O3 and BiFe0.97Ni0.03O3 (BFNO: Ni-doped BFO) ceramics were prepared by solid-state reaction and rapid sintering, and analyzed by structural and magnetic-property measurements. The leakage current density was measured at RT by using a standard ferroelectric tester. All the Ni-doped BFO samples exhibited the similar rhombohedral perovskite structure ( R3c) to that of BFO. The magnetic properties of Ni-doped BFO were much enhanced with respect to BFO prepared at the same conditions, because the enhanced ferromagnetic interaction is caused by the Fe/Ni coupling.

  1. Reinforced magnetic properties of Ni-doped BiFeO3 ceramic

    CERN Document Server

    Hwang, J S; Kang, J -H; Lee, K H; Lee, B W; Park, S Y; Lee, Y P

    2016-01-01

    Multiferroic materials attract considerable interest because of the wide range of potential applications such as spintronic devices, data storage and sensors. As a strong candidate for the applications among the limited list of single-phase multiferroic materials, BiFeO3 (BFO) is a quite attractive material due to its multiferroic properties at room temperature (RT). However, BFO is widely known to have large leakage current and small spontaneous polarization due to the existence of crystalline defects such as oxygen vacancies. Furthermore, the magnetic moment of pure BFO is very weak owing to its antiferromagnetic nature. In this paper, the effects of Ni2+ substitution on the magnetic properties of bulk BFO have been investigated. BFO, and BiFe0.99Ni0.01O3, BiFe0.98Ni0.02O3 and BiFe0.97Ni0.03O3 (BFNO: Ni-doped BFO) ceramics were prepared by solid-state reaction and rapid sintering, and analyzed by structural and magnetic-property measurements. The leakage current density was measured at RT by using a standar...

  2. Study on Ferroelectric and Dielectric Properties of La-Doped CaBi4Ti4O15-Based Ceramics

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Lanthanum doped bismuth layer structured ferroelectrics (BLSFs) Ca1-xLaxBi4(Ti0.9W0.1)4O15 (x=0, 0.2, 0.3, 0.4, 0.6) ceramics were prepared by solid-state reaction method. X-ray diffraction(XRD) patterns showed that single phase was formed when x=0~0.6. The effects of La3+ doping on dielectric, piezoelectric and ferroelectric properties of Ca1-xLaxBi4(Ti0.9W0.1)4O15 ceramics were studied. Ca0.7La0.3Bi4(Ti0.9W0.1)4O15 ceramic had optimal properties, its dielectric constant was 166.85, dielectric loss was 0.0063, piezoelectric strain constant was 11 pc·N-1, remanent polarization was 18.1 μC·cm-2 and coercive field was 118 kV·cm-1. SEM micrographs showed that the grains of CaBi4Ti4O15-based ceramics were plate-like. The results of energy spectrum analysis (EDS) showed that La3+ incorporation could increase Bi/Ca ratio.

  3. The Effect of Temperature Dependence of AC Losses in a Bi-2223/Ag Insert of an 8-T Superconducting Magnet

    DEFF Research Database (Denmark)

    Wang, Lei; Wang, Qiuliang; Wang, Hui;

    2016-01-01

    A conduction-cooled split-gap superconducting magnet system with a center field of 8 T has been designed and fabricated in the Institute of Electrical Engineering, Chinese Academy of Sciences. The system consists of two Bi-2223/Ag coils and six NbTi coils. Due to a large aspect ratio of the high...... dependence relations of the critical current density .1c are considered. The calculations are carried out in three steps. First, to estimate the magnitude of ac losses rapidly in the Bi-2223/Ag coils, the ac losses are calculated when the Bi-2223/Ag and NbTi coils are simultaneously charged, in which...... the temperature distribution is not considered. Second, the temperature variation is considered to calculate the ac losses under the same operating conditions with those in the first case. Finally, the NbTi coils are charged first, followed by the Bi-2223/Ag coils; the ac losses calculated are less than those...

  4. Distinct superconducting states in the pressure-induced metallic structures of the nominal semimetal Bi[subscript 4]Te[subscript 3

    Energy Technology Data Exchange (ETDEWEB)

    Jeffries, J.R.; Sharma, A.L. Lima; Sharma, P.A.; Spataru, C.D.; McCall, S.K.; Sugar, J.D.; Weir, S.T.; Vohra, Y.K. (Sandia); (LLNL); (UAB)

    2011-11-07

    The end members, Bi and Bi{sub 2}Te{sub 3}, of the infinitely adaptive (Bi{sub 2})m(Bi{sub 2}Te{sub 3}){sub n} series of compounds have not only been revealed to be topological insulators under the appropriate conditions, but have also been shown to be superconductors under pressure, suggesting the potential for bulk superconductor-topological-insulator interfaces and associated quantum computing applications. Herein, we report the pressure-dependent evolution of the structure and electrical transport of the nominal semimetal Bi4Te{sub 3}, a member of the (Bi{sub 2})m(Bi{sub 2}Te{sub 3}){sub n} series. Under pressure, Bi4Te{sub 3} undergoes several structural phase transformations, ultimately yielding a metallic body-centered-cubic structure exhibiting superconductivity with a maximum T{sub c} = 8.4 K at 16.2 GPa. The occurrence of structure-dependent superconductivity in Bi{sub 4}Te{sub 3} is remarkably similar to the end members of the (Bi{sub 2})m(Bi{sub 2}Te{sub 3}){sub n} series, intimating a convergence to high-pressure universal behavior that may expose the subtle variations that lead to the topological insulating and superconducting states in these systems.

  5. Doping of BiScO3-PbTiO3 Ceramics for Enhanced Properties

    Science.gov (United States)

    Sehirlioglu, Alp; Sayir, Ali; Dynys, Fred

    2008-01-01

    High-temperature piezoelectrics are a key technology for aeronautics and aerospace applications such as fuel modulation to increase the engine efficiency and decrease emissions. The principal challenge for the insertion of piezoelectric materials is the limitation on upper use temperature which is due to low Curie-Temperature (T(sub c) and increasing electrical conductivity. BiScO3 -PbTiO3 (BS-PT) system is a promising candidate for improving the operating temperature for piezoelectric actuators due to its high TC (>400 C). Effects of Zr and Mn doping of the BS-PT ceramics have been studied and all electrical and electromechanical properties for Sc-deficient and Ti-deficient BS- PT ceramics are reported as a function of electrical field and temperature. Donor doping with Zr and Mn (in Sc deficient compositions) increased the DC-resistivity and decreased tan at all temperatures. Resulting ceramics exhibited saturated hysteresis loops with low losses and showed no dependence on the applied field (above twice the coercive field) and measurement frequency.

  6. Microstructure and properties of Sm-substituted BiFeO3 ceramics

    Institute of Scientific and Technical Information of China (English)

    DAI Haiyang; CHEN Zhenping; LI Tao; LI Yong

    2012-01-01

    Bi1-xSmxFeO3 (x=0.00-0.15) ceramics were synthesized by sol-gel technique with rapid liquid phase sintering process to study the effects of samarium (Sm) substitution on their microstructure and properties.X-ray diffraction (XRD) and Raman studies showed that the structure of BiFeO3 was changed from rhombohedral to orthorhombic at the samarium substitution concentration about x=0.10.The SEM investigation suggested that the Sm substitution hindered the grain growth.Magnetic measurements showed that all the samples studied had a weak ferromagnetism,and the ferromagnetic property of BiFeO3 was improved by Sm substitution due to the suppressed or broken cycloid spin structure caused by the changes in the crystalline structure and size effect.The leakage current was found to be reduced with increasing Sm concentration.The dielectric and ferroelectric measurements showed that dielectric constant,dielectric loss and ferroelectric properties were strongly dependent on the Sm content,Sm substitution could significantly improve the dielectric constant,remnant polarization and decrease the dielectric loss due to the significant decrease of the electric leakage of the samples.

  7. Electronic structure of a superconducting topological insulator Sr-doped Bi{sub 2}Se{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Han, C. Q.; Chen, W. J.; Zhu, Fengfeng; Yao, Meng-Yu [Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Li, H.; Li, Z. J.; Wang, M.; Gao, Bo F., E-mail: bo-f-gao@mail.sim.ac.cn [Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Science, Shanghai 200050 (China); Guan, D. D.; Liu, Canhua; Qian, Dong, E-mail: dqian@sjtu.edu.cn; Jia, Jin-Feng [Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093 (China); Gao, C. L. [Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093 (China); Department of Physics, Fudan University, Shanghai 200433 (China)

    2015-10-26

    Using high-resolution angle-resolved photoemission spectroscopy and scanning tunneling microscopy/spectroscopy, the atomic and low energy electronic structure of the Sr-doped superconducting topological insulators (Sr{sub x}Bi{sub 2}Se{sub 3}) was studied. Scanning tunneling microscopy shows that most of the Sr atoms are not in the van der Waals gap. After Sr doping, the Fermi level was found to move further upwards when compared with the parent compound Bi{sub 2}Se{sub 3}, which is consistent with the low carrier density in this system. The topological surface state was clearly observed, and the position of the Dirac point was determined in all doped samples. The surface state is well separated from the bulk conduction bands in the momentum space. The persistence of separated topological surface state combined with small Fermi energy makes this superconducting material a very promising candidate for the time reversal invariant topological superconductor.

  8. Improvement of mechanical characteristics and performances with Ni diffusion mechanism throughout Bi-2223 superconducting matrix

    Science.gov (United States)

    Sarıtekin, N. K.; Bilge, H.; Kahraman, M. F.; Zalaoǧlu, Y.; Pakdil, M.; Doǧruer, M.; Yıldırım, G.; Oz, M.

    2016-03-01

    This study is interested in the role of diffusion annealing temperature (650-850°C) on the mechanical characteristics and performance of pure and Ni diffused Bi-2223 superconducting materials by means of standard compression tests and Vickers hardness measurements at performed different applied loads in the range of 0.245-2.940N and theoretical calculations. Based on the experimental findings, the mechanical performances improve with increasing annealing temperature up to 700 °C beyond which they degrade drastically due to the increased artificial disorders, cracks and irregular grain orientation distribution. In other words, the penetration of excess Ni inclusions accelerates both the dislocation movement and especially the cracks and voids propagation as a result of the decrement in the Griffith critical crack length. Further, it is to be mentioned here that all the sample exhibit typical indentation size effect (ISE) behavior. In this respect, both the plastic (irreversible) and elastic (reversible) deformations have dominant role on the superconducting structures as a result of the enhancement in the elastic recovery. At the same time elastic modulus, yield strength and fracture toughness parameters are theoretically extracted from the microhardness values. Moreover, the elastic modulus parameters are compared with the experimental values. It is found that the differentiation between the comparison results enhances hastily with the increment in the applied indentation test loads due to the existence of the increased permanent disorders, lattice defects and strains in the stacked layers. Namely, the error level increases away from the actual crystal structure. Additionally, the microhardness values are theoretically analyzed for the change of the mechanical behaviors with the aid of Meyer's law, elastic/plastic deformation and Hays-Kendall approaches for the first time.

  9. Spin-orbit coupling enhanced superconductivity in Bi-rich compounds ABi₃ (A = Sr and Ba).

    Science.gov (United States)

    Shao, D F; Luo, X; Lu, W J; Hu, L; Zhu, X D; Song, W H; Zhu, X B; Sun, Y P

    2016-02-19

    Recently, Bi-based compounds have attracted attentions because of the strong spin-orbit coupling (SOC). In this work, we figured out the role of SOC in ABi3 (A = Sr and Ba) by theoretical investigation of the band structures, phonon properties, and electron-phonon coupling. Without SOC, strong Fermi surface nesting leads to phonon instabilities in ABi3. SOC suppresses the nesting and stabilizes the structure. Moreover, without SOC the calculation largely underestimates the superconducting transition temperatures (Tc), while with SOC the calculated Tc are very close to those determined by measurements on single crystal samples. The SOC enhanced superconductivity in ABi3 is due to not only the SOC induced phonon softening, but also the SOC related increase of electron-phonon coupling matrix elements. ABi3 can be potential platforms to construct heterostructure of superconductor/topological insulator to realize topological superconductivity.

  10. Mn-doping induced ferromagnetism and enhanced superconductivity in Bi4 -xMnxO4S3 (0.075 ≤x ≤0.15 )

    Science.gov (United States)

    Feng, Zhenjie; Yin, Xunqing; Cao, Yiming; Peng, Xianglian; Gao, Tian; Yu, Chuan; Chen, Jingzhe; Kang, Baojuan; Lu, Bo; Guo, Juan; Li, Qing; Tseng, Wei-Shiuan; Ma, Zhongquan; Jing, Chao; Cao, Shixun; Zhang, Jincang; Yeh, N.-C.

    2016-08-01

    We demonstrate that Mn doping in the layered sulfides Bi4O4S3 leads to stable Bi4-xMnxO4S3 compounds that exhibit both long-range ferromagnetism and enhanced superconductivity for 0.075 ≤x ≤0.15 , with a possible record superconducting transition temperature (Tc) ˜15 K among all BiS2-based superconductors. We conjecture that the coexistence of superconductivity and ferromagnetism may be attributed to Mn doping in the spacer Bi2O2 layers away from the superconducting BiS2 layers, whereas the enhancement of Tc may be due to excess electron transfer to BiS2 from the Mn4 +/Mn3 + substitutions in Bi2O2 . This notion is empirically corroborated by the increased electron-carrier densities upon Mn doping, and by further studies of the Bi4-xAxO4S3 compounds (A = Co, Ni; x =0.1 , 0.125), where the Tc values remain comparable to that of the undoped Bi4O4S3 system (˜4.5 K) due to lack of 4+ valences in either Co or Ni ions for excess electron transfer to the BiS2 layers. These findings therefore shed new light on feasible pathways to enhance the Tc values of BiS2-based superconductors, although complete elucidation of the interplay between superconductivity and ferromagnetism in these anisotropic layered compounds awaits the development of single crystalline materials for further investigation.

  11. Grains and grain boundaries contribution to dielectric relaxations and conduction of Bi5Ti3FeO15 ceramics

    Science.gov (United States)

    Rehman, Fida; Li, Jing-Bo; Zhang, Jia-Song; Rizwan, Muhammad; Niu, Changlei; Jin, Hai-Bo

    2015-12-01

    Dielectric relaxation behaviors of Aurivillius Bi5Ti3FeO15 ceramics were investigated in a wide range of frequency and temperature via dielectric and impedance spectroscopies. We distinguished two dielectric relaxations using the combination of impedance and modulus analysis. Resistance of the grain boundary was found to be much larger than grains, whereas capacitance was at the same level. The kinetic analysis of dielectric data was carried out to evaluate the contributions of microstructure and defects to the relaxation and conduction. The possible relaxation-conduction mechanism in the ceramics was discussed. The results enable deep understanding of microstructure-defect-relaxation behaviors in Bi5Ti3FeO15 ceramics.

  12. Manganese-Nanoparticles Substitutions on the Vanadium Sites of Bi-Sr-Vanadate Aurivillius Ceramics

    Directory of Open Access Journals (Sweden)

    Khaled M. Elsabawy

    2012-01-01

    Full Text Available The aurivillius phase of Mn-substituted samples with general formula Bi2SrV2−MnO9, where =0.05,0.1,0.2,0.3, and 0.6 mole were prepared by solid-state reaction technique and ceramics procedures. The X-ray structural measurement analysis confirmed the formation of single-phase-layered hexagonal structure which is observed in all samples. The thermal stability and phase change of the green powders were studied by thermogravimetric analysis (TGA and differential thermal analysis (DTA. SEM revealed that the average grain size increases with increasing Mn content. The infrared absorption spectra recorded a series of vibrational modes within the range of 400–1600 cm−1 were investigated. The present work also studied the effect of Mn-doping concentration interactions on both DC-electrical conductivity and ESR spectra.

  13. Structural, dielectric and multiferroic properties of Er and La substituted BiFeO3 ceramics

    Indian Academy of Sciences (India)

    Pragya Pandit; S Satapathy; Poorva Sharma; P K Gupta; S M Yusuf; V G Sathe

    2011-07-01

    Erbium (Er) and lanthanum (La) substituted BiFeO3 (BFO) ceramics have been prepared through conventional solid solution route. X-ray diffraction data indicated a gradual phase transition from rhombohedral to monoclinic structure in Bi0.9– La0.1Er FeO3 ( = 0.05, 0.07 and 0.1) (BLEFO = 0.05, 0.07,0.1) ceramics. Differential thermal analysis (DTA) measurements of BFO samples showed a ferroelectric transition at 835°C, whereas it is shifted to 792°C for BLEFO = 0.1. The Raman spectra of BLEFO = 0.05,0.07,0.1 samples showed the shift of Raman modes to higher wavenumbers and suppression of A1 modes indicating decrease in ferroelectricity. The Raman spectra also indicated the structural transformation due to Er and La substitution in BFO. On subsequent erbium doping, the intrinsic dielectric constant is found to decrease from 68 (for pure BFO) to 52 for BLEFO = 0.05 to 43 for BLEFO = 0.07 but increased to 89 for BLEFO = 0.1 when compared to pure BFO. The increase in Er content resulted in the increase in spontaneous magnetization (0.1178 emu/g at 8T for BLEFO = 0.1) due to collapse of spin cycloid structure. Ferroelectric remnant polarization of BLEFO = 0.05 and BLEFO = 0.07 decreases when compared to pure BFO while small remnant polarization (close to paraelectric behaviour) is evident for BLEFO = 0.1.

  14. Structure and superconductivity in (Bi(0.35)Cu(0.65))Sr2YCu2O7 and related materials

    Science.gov (United States)

    Jennings, R. A.; Williams, S. P.; Greaves, C.

    1995-01-01

    The recently reported (Bi/Cu)Sr2YCu2O7 phase has been studied by time of flight powder neutron diffraction. The proposed 1212 structure has been confirmed and refinements have shown the oxygen in the (Bi/Cu)O layer is displaced by 0.78 A from the ideal (1/2,1/2,0) site (P4/mmm space group) along /100/. Bond Valence Sum calculations have suggested oxidation states of Bi(5+) and Cu(2+) for the cations in the (Bi/Cu)O layers. The material is non-superconducting and all attempts to induce superconductivity have been unsuccessful. Work on the related material (Ce/Cu)Sr2YCu2O7 has shown the ideal Ce content to be 0.5 Ce per formula unit. The introduction of Ba (10%) onto the Sr site dramatically increases phase stability and also induces superconductivity (62 K).

  15. Effect of MgO nanoparticles embedded into Bi-2212/Ag tapes on the microstructure and superconducting properties

    Energy Technology Data Exchange (ETDEWEB)

    Ilyushechkin, Alexander Y. [CSIRO, Pullenvale 4069, QLD (Australia); Agranovski, Igor E., E-mail: i.agranovski@griffith.edu.a [Griffith School of Engineering, Griffith University, 170 Kessels Rd, Nathan, Brisbane 4111, QLD (Australia); Altman, Igor S. [Griffith School of Engineering, Griffith University, 170 Kessels Rd, Nathan, Brisbane 4111, QLD (Australia); Institute of Advanced Machinery and Design, Seoul National University, Seoul 151-742 (Korea, Republic of); Choi, Mansoo [Institute of Advanced Machinery and Design, Seoul National University, Seoul 151-742 (Korea, Republic of)

    2010-02-25

    Magnesium oxide nanoparticles embedded into Bi-2212/Ag tapes may significantly improve transport properties of the tapes in magnetic fields as flux pinning centres. The effect of the addition of ultra-fine MgO particles, obtained by Mg combustion, in Bi-2212/Ag tapes was investigated in order to improve critical current densities of the tapes in magnetic fields. Optimization of the MgO concentration and uniformity of the MgO particles distribution across the tapes were also investigated. Microstructure of Bi-2212 ceramic layer and J{sub c} of the tapes were enhanced with addition of MgO nanoparticles with concentrations of up to 4 wt.%. Higher MgO concentrations lead to degradation of the samples' microstructure and a corresponding decrease of absolute J{sub c} values in self-field.

  16. Dielectric and piezoelectric properties of (Li, Ce) modified NaBi5Ti5O18composite ceramics

    Institute of Scientific and Technical Information of China (English)

    MA Lei; ZHAO Kun; LI Jixia; WU Qi; ZHAO Minglei; WANG Chunlei

    2009-01-01

    Nominal (Li0.5Ce0.5)x(Na0.5Bi0.5)(1-x)Na0.5Bi4.5Ti5O18 composite ceramics were fabricated using conventional solid-state reaction method. The coexistence of bismuth layer-structured phase and perovskite phase was determined in these ceramics using XRD technique. At room temperature, the x=0.11 sample showed the largest piezoelectric constant, d33, of about 26.5 pC/N and the largest electromechanical coupling factor, kt, of about 30%. Even after annealing at 500 ℃, the value of d33 was still about 19 pC/N, in x=0.08-0.11 samples. Moreover, these composite ceramics showed low temperature coefficients of dielectric constant and high electrical resistivity in the temperature region of 450-550 ℃. These results indicated that (Li, Ce) modified NaBi5Ti5O18 composite ceramics were promising piezoelectric materials for high-temperature applications.

  17. Superconductivity

    CERN Document Server

    Thomas, D B

    1974-01-01

    A short general review is presented of the progress made in applied superconductivity as a result of work performed in connection with the high-energy physics program in Europe. The phenomenon of superconductivity and properties of superconductors of Types I and II are outlined. The main body of the paper deals with the development of niobium-titanium superconducting magnets and of radio-frequency superconducting cavities and accelerating structures. Examples of applications in and for high-energy physics experiments are given, including the large superconducting magnet for the Big European Bubble Chamber, prototype synchrotron magnets for the Super Proton Synchrotron, superconducting d.c. beam line magnets, and superconducting RF cavities for use in various laboratories. (0 refs).

  18. Formation of the 110-K superconducting phase in Pb-doped Bi-Sr-Ca-Cu-O thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kula, W.; Sobolewski, R.; Gorecka, J.; Lewandowski, S.J. (Instytut Fizyki, Polska Akademia Nauk, Al. Lotnikow 32/46, PL-02668 Warszawa (Poland))

    1991-09-15

    Investigation of the 110-K Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub {ital x}} phase formation in superconducting thin films of Bi-based cuprates is reported. The films were dc magnetron sputtered from single Bi(Pb)-Sr-Ca-Cu-O targets of various stoichiometries, and subsequently annealed in air at high temperatures. The influence of the initial Pb content, annealing conditions, as well as the substrate material on the growth of the 110-K phase was investigated. We found that the films, fully superconducting above 100 K could be reproducibly fabricated on various dielectric substrates from Pb-rich targets by optimizing annealing conditions for each initial Pb/Bi ratio. Heavy Pb doping considerably accelerated formation of the 110-K phase, reducing the film annealing time to less than 1 h. Films containing, according to the x-ray measurement, more than 90% of the 110-K phase were obtained on MgO substrates, after sputtering from the Bi{sub 2}Pb{sub 2.5}Sr{sub 2}Ca{sub 2.15}Cu{sub 3.3}O{sub {ital x}} target and annealing in air for 1 h at 870 {degree}C. The films were {ital c}-axis oriented, with 4.5-K-wide superconducting transition, and zero resistivity at 106 K. Their critical current density was 2 {times} 10{sup 2} A/cm{sup 2} at 90 K, and above 10{sup 4} A/cm{sup 2} below 60 K. The growth of the 110-K phase on epitaxial substrates, such as CaNdAlO{sub 4} and SrTiO{sub 3}, was considerably deteriorated, and the presence of the 80- and 10-K phases was detected. Nevertheless, the best films deposited on these substrates were fully superconducting at 104 K and exhibited critical current densities above 2 {times} 10{sup 5} A/cm{sup 2} below 60 K{minus}one order of magnitude greater than the films deposited on MgO.

  19. Enhancement of superconductivity near the pressure-induced semiconductor-metal transition in the BiS₂-based superconductors LnO₀.₅F₀.₅BiS₂ (Ln = La, Ce, Pr, Nd).

    Science.gov (United States)

    Wolowiec, C T; White, B D; Jeon, I; Yazici, D; Huang, K; Maple, M B

    2013-10-23

    Measurements of electrical resistivity were performed between 3 and 300 K at various pressures up to 2.8 GPa on the BiS2-based superconductors LnO0.5F0.5BiS2 (Ln=Pr, Nd). At lower pressures, PrO0.5F0.5BiS2 and NdO0.5F0.5BiS2 exhibit superconductivity with critical temperatures Tc of 3.5 and 3.9 K, respectively. As pressure is increased, both compounds undergo a transition at a pressure Pt from a low Tc superconducting phase to a high Tc superconducting phase in which Tc reaches maximum values of 7.6 and 6.4 K for PrO0.5F0.5BiS2 and NdO0.5F0.5BiS2, respectively. The pressure-induced transition is characterized by a rapid increase in Tc within a small range in pressure of ∼0.3 GPa for both compounds. In the normal state of PrO0.5F0.5BiS2, the transition pressure Pt correlates with the pressure where the suppression of semiconducting behaviour saturates. In the normal state of NdO0.5F0.5BiS2, Pt is coincident with a semiconductor-metal transition. This behaviour is similar to the results recently reported for the LnO0.5F0.5BiS2 (Ln=La, Ce) compounds. We observe that Pt and the size of the jump in Tc between the two superconducting phases both scale with the lanthanide element in LnO0.5F0.5BiS2 (Ln=La, Ce, Pr, Nd).

  20. RVB states in doped band insulators from Coulomb forces: theory and a case study of superconductivity in BiS2 layers

    Science.gov (United States)

    Baskaran, G.

    2016-12-01

    Doped band insulators, HfNCl, WO3, diamond, Bi2Se3, BiS2 families, STO/LAO interface, gate doped SrTiO3, MoS2 and so on are unusual superconductors. With an aim to build a general theory for superconductivity in doped band insulators, we focus on the BiS2 family which was discovered by Mizuguchi et al in 2012. While maximum Tc is only ˜11 K in {{LaO}}1-{{x}}{{{F}}}{{x}}{{BiS}}2, a number of experimental results are puzzling and anomalous in the sense that they resemble high T c and unconventional superconductors. Using a two orbital model of Usui, Suzuki and Kuroki, we show that the uniform low density free Fermi sea in {{LaO}}{0,5}{{{F}}}0.5{{BiS}}2 is unstable towards formation of the next nearest neighbor Bi-S-Bi diagonal valence bond (charged -2e Cooper pair) and their Wigner crystallization. Instability to this novel state of matter is caused by unscreened nearest neighbor coulomb repulsions (V ˜ 1 eV) and a hopping pattern with sulfur mediated diagonal next nearest neighbor Bi-S-Bi hopping t’ ˜ 0.88 eV, as well as larger than nearest neighbor Bi-Bi hopping, t ˜ 0.16 eV. Wigner crystals of Cooper pairs quantum melt for doping around x = 0.5 and stabilize certain resonating valence bond states and superconductivity. We study a few variational RVB states and suggest that BiS2 family members are latent high Tc superconductors, but challenged by competing orders and the fragile nature of many body states sustained by unscreened Coulomb forces. One of our superconducting states has d XY symmetry and a gap. We also predict a 2d Bose metal or vortex liquid normal state, as charged -2e valence bonds survive in the normal state.

  1. Detailed magnetization study of superconducting properties of YBa2Cu3O7-x ceramic spheres

    Science.gov (United States)

    Landau, I. L.; Willems, J. B.; Hulliger, J.

    2008-03-01

    We present a magnetization study of low density YBa2Cu3O7-x ceramics carried out in magnetic fields H such that 0.5 Oe85 K, using low field magnetization measurements, we were able to evaluate the temperature dependence of λ, which turned out to be very close to predictions from conventional Ginzburg-Landau theory. Although the present samples consisted of randomly oriented grains, specifics of magnetization measurements allowed for evaluation of λab(T). Good agreement between our estimation of the grain size and the real sample structure provides evidence for the validity of this analysis of magnetization data. Measurements of the equilibrium magnetization in high magnetic fields were used for evaluation of Hc2(T). At temperatures close to Tc, the Hc2(T) dependence turned out to be linear, in agreement with Ginzburg-Landau theory. The value of the temperature at which Hc2 vanishes coincides with the superconducting critical temperature evaluated from low field measurements, which is important evidence of the validity of both approaches to the analysis of magnetization data.

  2. Novel effects of weak magnetic fields on post-implantation damage in semiconductors and superconducting ceramics

    Science.gov (United States)

    Khait, Yu. L.

    1996-08-01

    Novel experimentally verifiable and theoretically explained effects of weak static magnetic fields (WSMFs) acting during ion implantation of semiconductors and superconducting ceramics (SCC) at 300 K, moderate ion energies (e.g. 200-400 keV) and low dosage (e.g. 10 11-10 13 m -2) on the post-implantation radiation damage (PIRD) and material parameters are discussed. The WSMF of strength of H ≈ 1 kOe reduces, as previously reported, the PIRD in Hg 08Cd 02Te and InSb by factors of 2 and 1.54, respectively, and can increase the PIRD and change material parameters in SCCs. The WSMF effects on the radiation damage is a generic consequence of the kinetic electron-related theory of atomic rate processes in solids which shows that local electron transitions (LETs) in the nanometer vicinity of hopping atoms (defects) influence exponentially defect formation and migration rates. The magnetic field changing the LET number affects exponentially the rates of formation, migration and agglomeration of point defects and thus change the radiation damage.

  3. Novel effects of weak magnetic fields on post-implantation damage in semiconductors and superconducting ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Khait, Y.L. [Technion-Israel Inst. of Tech., Haifa (Israel). Solid State Inst.

    1996-08-01

    Novel experimentally verifiable and theoretically explained effects of weak static magnetic fields (WSMFs) acting during ion implantation of semiconductors and superconducting ceramics (SCC) at 300 K, moderate ion energies (e.g. 200-400 keV) and low dosage (e.g. 10{sup 11}-10{sup 13} m{sup -2}) on the post-implantation radiation damage (PIRD) and material parameters are discussed. The WSMF of strength of H{approx}1 kOe reduces, as previously reported, the PIRD in Hg{sub 08}Cd{sub 02}Te and InSb by factors of 2 and 1.54, respectively, and can increase the PIRD and change material parameters in SCCs. The WSMF effects on the radiation damage is a generic consequence of the kinetic electron-related theory of atomic rate processes in solids which shows that local electron transitions (LETs) in the nanometer vicinity of hopping atoms (defects) influence exponentially defect formation and migration rates. The magnetic field changing the LET number affects exponentially the rates of formation, migration and agglomeration of point defects and thus change the radiation damage. (orig.).

  4. Miniature ceramic-anvil high-pressure cell for magnetic measurements in a commercial superconducting quantum interference device magnetometer.

    Science.gov (United States)

    Tateiwa, Naoyuki; Haga, Yoshinori; Fisk, Zachary; Ōnuki, Yoshichika

    2011-05-01

    A miniature opposed-anvil high-pressure cell has been developed for magnetic measurement in a commercial superconducting quantum interference device magnetometer. Non-magnetic anvils made of composite ceramic material were used to generate high-pressure with a Cu-Be gasket. We have examined anvils with different culet sizes (1.8, 1.6, 1.4, 1.2, 1.0, 0.8, and 0.6 mm). The pressure generated at low temperature was determined by the pressure dependence of the superconducting transition of lead (Pb). The maximum pressure P(max) depends on the culet size of the anvil: the values of P(max) are 2.4 and 7.6 GPa for 1.8 and 0.6 mm culet anvils, respectively. We revealed that the composite ceramic anvil has potential to generate high-pressure above 5 GPa. The background magnetization of the Cu-Be gasket is generally two orders of magnitude smaller than the Ni-Cr-Al gasket for the indenter cell. The present cell can be used not only with ferromagnetic and superconducting materials with large magnetization but also with antiferromagnetic compounds with smaller magnetization. The production cost of the present pressure cell is about one tenth of that of a diamond anvil cell. The anvil alignment mechanism is not necessary in the present pressure cell because of the strong fracture toughness (6.5 MPa m(1∕2)) of the composite ceramic anvil. The simplified pressure cell is easy-to-use for researchers who are not familiar with high-pressure technology. Representative results on the magnetization of superconducting MgB(2) and antiferromagnet CePd(5)Al(2) are reported.

  5. Electrical Characteristics and Microstructures of Sm2O3-Doped Bi4Ti3O12 Ceramics

    Institute of Scientific and Technical Information of China (English)

    陈敏; 王豫; 刘祖黎; 董亮; 羊新胜; 姚凯伦

    2004-01-01

    We investigate the electrical properties of Sm-doped Bi4-xSmx Ti3O12 (BST) ceramics prepared by a conventional electroceramic technique. The x-ray diffraction analysis reveals the Bi-layered perovskite structure in all samples.The SEM micrographs show randomly oriented and plate-like morphology. For the samples with x = 0.4 and 1.0,the current-voltage characteristics exhibit negative differential resistance behaviour and the P-V hysteresis loops are characterized by large leakage current, whereas for the samples with x = 0.6 and 0.8, the current-voltage characteristics show simple ohmic behaviour and the P-V hysteresis loops are of the saturated and undistorted hysteresis. The remanent polarization and coercive field of the BST ceramic with x = 0.8 are above 32μC/cm2and 70kV/cm, respectively.

  6. Superconductivity

    Science.gov (United States)

    1989-07-01

    SUPERCONDUCTIVITY HIGH-POWER APPLICATIONS Electric power generation/transmission Energy storage Acoustic projectors Weapon launchers Catapult Ship propulsion • • • Stabilized...temperature superconductive shields could be substantially enhanced by use of high-Tc materials. 27 28 NRAC SUPERCONDUCTIVITY SHIP PROPULSION APPLICATIONS...motor shown in the photograph. As a next step in the evolution of electric-drive ship propulsion technology, DTRC has proposed to scale up the design

  7. Structural Transition and Enhanced Ferromagnetic Properties of La, Nd, Gd, and Dy-Doped BiFeO3 Ceramics

    Science.gov (United States)

    Kumar, Ashwini; Varshney, Dinesh

    2015-11-01

    The structural, electrical, and magnetic properties of rare-earth-doped Bi0.8 RE0.2FeO3 ceramics (rare-earth (RE) = La, Nd, Gd, and Dy) synthesized by solid-state reaction are reported and discussed. The x-ray diffraction (XRD) patterns of Bi0.8La0.2FeO3 and Bi0.8Nd0.2FeO3 were indexed to rhombohedral ( R3 c) and triclinic ( P1) structures, respectively. Rietveld refinement of the XRD pattern of Bi0.8Dy0.2FeO3 confirmed its biphasic nature ( Pnma + R3 c space groups) whereas for Bi0.8Gd0.2FeO3 the orthorhombic phase with Pna21 symmetry made a major contribution, with minor contributions from the orthorhombic ( Pnma) and rhombohedral ( R3 c) phases. Raman spectroscopy revealed changes in BiFeO3 mode positions, in addition to structural changes, on RE ion substitution. The effect of RE ion substitution on dielectric constant and loss tangent were studied at room temperature in a wide range of frequency, 50 Hz-1 MHz. Room temperature magnetization-magnetic field ( M- H) measurements indicated that magnetization increased with increasing structural distortion and with partial destruction of the spin cycloid as a result of doping of BiFeO3 ceramics with rare earth ions. These compounds, with improved remnant magnetization and coercive field, are suitable for use in spin-based electronic devices.

  8. Superconducting fluctuations: paraconductivity, excess Hall effect and magnetoconductivity in 2223-BiSrCaCuO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Lang, W. (Ludwig Boltzmann Inst. fuer Festkoerperphysik, Wien (Austria) Inst. fuer Festkoerperphysik, Univ. Wien (Austria)); Kula, W. (Dept. of Electrical Engineering and Lab. for Laser Energetics, Univ. of Rochester, NY (United States) Inst. of Physics, Polish Academy of Sciences, Warszawa (Poland)); Sobolewski, R. (Dept. of Electrical Engineering and Lab. for Laser Energetics, Univ. of Rochester, NY (United States) Inst. of Physics, Polish Academy of Sciences, Warszawa (Poland))

    1994-02-01

    We report a detailed study of the influence of thermodynamic fluctuations of the superconducting order parameter on various normal-state transport properties in 2223-(Bi,Pb)SrCaCuO thin films at temperatures near the superconducting transition. Measurements of the electrical resistivity, the magnetoresistance and the Hall effect were analyzed with regard to fluctuation contributions, using theories for 2-dimensional, layered superconductors. We obtained a consistent set of parameters, which fit all magneto-transport measurements above 118 K, but observed a remarkable enhancement of both excess Hall effect and negative magnetoconductivity closer to T[sub c], whereas the zero-field fluctuation conductivity follows the theoretical predictions down to 110 K. No significant contributions from the indirect (Maki-Thompson) fluctuations process were found. (orig.)

  9. Contribution of an extrinsic mechanism for the electrical polarization in BiMn2O5 ceramics

    Directory of Open Access Journals (Sweden)

    I. Fier

    2012-12-01

    Full Text Available DC conductivity, frequency dependent dielectric constant and pyroelectric coefficients, obtained from thermal stimulated depolarization current curves, in BiMn2O5 ceramics in the range of temperatures from 10 K to 320 K are reported. The data could be explained if it is assumed that a dipole defect is formed due to an oxygen vacancy and two manganese ions which have their valence changed to accept an electron.

  10. Contribution of an extrinsic mechanism for the electrical polarization in BiMn{sub 2}O{sub 5} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Fier, I.; Chinaglia, D. L.; Walmsley, L. [Departamento de Fisica, Instituto de Geociencias e Ciencias Exatas, Universidade Estadual Paulista (UNESP) Caixa Postal 178, CEP 13500-970, Rio Claro, Sao Paulo (Brazil); Pereira, E. C.; Rabelo, A. C.; Freitas, R. G. [Departamento de Quimica, Universidade Federal de Sao Carlos, C.P. 676, CEP13560-970, Sao Carlos, SP (Brazil)

    2012-12-15

    DC conductivity, frequency dependent dielectric constant and pyroelectric coefficients, obtained from thermal stimulated depolarization current curves, in BiMn{sub 2}O{sub 5} ceramics in the range of temperatures from 10 K to 320 K are reported. The data could be explained if it is assumed that a dipole defect is formed due to an oxygen vacancy and two manganese ions which have their valence changed to accept an electron.

  11. Seebeck effect in superconducting BaPb sub(1-x)Bi sub(x) O/sub 3/ system

    Energy Technology Data Exchange (ETDEWEB)

    Tani, T.; Itoh, T.; Tanaka, S. (Tokyo Univ. (Japan). Faculty of Engineering)

    1980-01-01

    Seebeck effect was observed on superconducting BaPb sub(1-x)Bi sub(x)O/sub 3/ system in x = 0 -- 0.4 from 4.2K or T sub(c) to 300K. Seebeck coefficient seems to consist of two contributions; one from the dominant metallic electrons and the other from additional unidentified carriers with fairly low mobility. The calculated epsilon sub(F), N(epsilon sub(F)) and m* from the metallic contribution tend to increase with x to maxima around x = 0.2, where T sub(c) also becomes maximum.

  12. Coexistence of superconductivity and complex 4 f magnetism in Eu0.5Ce0.5BiS2F.

    Science.gov (United States)

    Zhai, Hui-Fei; Zhang, Pan; Tang, Zhang-Tu; Bao, Jin-Ke; Jiang, Hao; Feng, Chun-Mu; Xu, Zhu-An; Cao, Guang-Han

    2015-09-30

    EuBiS2F is a self-doped superconductor due to the mixed valence of Eu. Here we report that, with the Ce substitution for Eu by 50 at.%, the material exhibits ferromagnetic ordering at 8 K for the Ce-4 f moment, superconductivity at 2.2 K in the BiS2 layers and possibly antiferromagnetic ordering at 2.1 K for the Eu-4 f spins. The Eu valence is essentially divalent with the Ce incorporation. We tentatively interpret the coexistence of ferromagnetism and superconductivity by considering different Bi-6p orbitals that are responsible for the superconductivity itself and for mediating the ferromagnetic interaction, respectively. We argue that the antiferromagnetic ordering of the Eu-4 f spins is most likely due to a magnetic dipole-dipole interaction.

  13. Magnetic and ferroelectric characteristics of Gd$^{3+}$ and Ti$^{4+}$ co-doped BiFeO$_3$ ceramics

    Indian Academy of Sciences (India)

    SHIVANAND MADOLAPPA; A V ANUPAMA; P W JASCHIN; K B R VARMA; B SAHOO

    2016-04-01

    Polycrystalline BiFeO3 and Bi$_{0.9}$Gd$_{0.1}$Fe$_{1−x}$Ti$_x$O$_3$ ($x = 0$, 0.01, 0.05 and 0.1) samples were synthesized by solid-state reaction route. Structural, magnetic and ferroelectric properties of these samples were investigated. X-ray powder diffraction (XRD) results confirmed the presence of a significant amount of Bi$_2$Fe$_4$O$_9$ impurity phase in the undoped BiFeO$_3$ sample. Mössbauer spectroscopy studies corroborated the XRD studies to confirm the presence of impurity phase.We have observed that gadolinium (Gd$^{3+}$) and titanium (Ti$^{4+}$) doping, respectively, on Bi$^{3+}$ and Fe$^{3+}$ sites facilitated a significant reduction in the impurity phase formation in BiFeO$_3$. Interestingly, Gd$^{3+}$-doping significantly reduced the impurity phase formation as compared to the undoped BiFeO$_3$ sample. This impurity phase formation was further overcome by doping higher ($x \\ge 0.05$) amounts of Ti in BiFeO$_3$. The crystallographicsite occupancies of Gd and Ti were confirmed by Rietveld refinement of XRD data,Mössbauer spectroscopy and magnetization measurements. An enhancement in ferromagnetic properties along with moderate ferroelectricproperties have been observed after co-doping. There was an increasing trend in remnant polarization (Pr) with the increase in Ti concentration besides an improvement in the characteristic saturation magnetization. Our resultsdemonstrate that Gd$^{3+}$ and Ti$^{4+}$ doping could be used to enhance multifunctional properties of BiFeO3 ceramics to enable them as potential material for various devices.

  14. Performance of titanium oxide-polymer insulation in superconducting coils made of Bi-2212/Ag-alloy round wire

    Science.gov (United States)

    Chen, Peng; Trociewitz, Ulf P.; Dalban-Canassy, Matthieu; Jiang, Jianyi; Hellstrom, Eric E.; Larbalestier, David C.

    2013-07-01

    Conductor insulation is one of the key components needed to make Ag-alloy clad Bi2Sr2CaCu2O8+x (Bi-2212/Ag) superconducting round wire (RW) successful for high field magnet applications, as dielectric standoff and high winding current densities (Jw) directly depend on it. In this study, a TiO2-polymer insulation coating developed by nGimat LLC was applied to test samples and a high field test coil. The insulation was investigated by differential thermal analysis (DTA), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), dielectric property measurement, and transport critical current (Ic) property measurement. About 29% of the insulation by weight is polymer. When the Bi-2212/Ag wire is fully heat treated, this decomposes with slow heating to 400 ° C in pure O2. After the full reaction, we found that the TiO2 did not degrade the critical current properties, adhered well to the conductor, and provided a breakdown voltage of more than 100 V, which allowed the test coil to survive quenching in 31.2 T background field, while providing a 2.6 T field increment. For Bi-2212/Ag RW with a typical diameter of 1.0-1.5 mm, this ˜15 μm thick insulation allows a very high coil packing factor of ˜0.74, whereas earlier alumino-silicate braid insulation only allows packing factors of 0.38-0.48.

  15. Non-isothermal crystallization kinetics and phase transformation of Bi2O3-SiO2 glass-ceramics

    Directory of Open Access Journals (Sweden)

    Guo H.W.

    2011-01-01

    Full Text Available The Bi2O3-SiO2 (BS glass-ceramics were prepared by melt-quench technique, and the crystallization kinetics and phase transformation behavior were investigated in accordance with Kissinger and Johson-Mehl-Avrami equation, DSC, XRD and SEM. The results show that in the heat treatment process (or termed as re-crystallizing process Bi2SiO5 and Bi4Si3O12 crystals were found consequently. Respectively, the crystallization activation energies of the two crystals are Ep1=14.8kJ/mol and Ep2=34.1kJ/mol. And the average crystallization index of n1=1.73 and n2=1.38 suggested volume nucleation, one-dimensional growth and surface nucleation, one-dimensional growth from surface to the inside respectively. The meta-stable needle-like Bi2SiO5 crystals are easily to be transformed into stable prismatic Bi4Si3O12 crystals. By quenching the melt and hold in 850°C for 1h, the homogenous single Bi4Si3O12 crystals were found in the polycrystalline phase of the BS glassceramics system.

  16. Structural and Magnetic Properties of Bi0.5Sr0.5FeO3 Multiferroic Ceramics

    Science.gov (United States)

    Puhan, Ashalata; Bhushan, Bhavya; Rout, Dibyaranjan

    2016-09-01

    Phase pure BiFeO3 (BFO) and Bi0.5Sr0.5FeO3 (BFSO) ceramics were synthesized by solid state reaction method at different sintering conditions. Structural characterization with XRD revealed that the rhombohedral phase changed to cubic due to substitution of Sr in the A- site of BFO. SEM micrographs of BSFO samples indicated improved microstructure with higher density particularly the samples sintered for longer durations. The XPS data suggested the change in oxidation state of Fe from Fe3+ to Fe2+ as a result of aliovalent substitution of Sr at Bi site. As a consequence, oxygen vacancies were created to neutralize charge disorder. The BSFO samples exhibited ferromagnetism with enhanced remnant magnetization and coercive field as compared to the linear magnetization in BFO. These improved results obtained by Sr doping were majorly due to the structural change and creation of oxygen vacancies.

  17. Phonon and magnon scattering of Bi{sub 2}Fe{sub 4}O{sub 9} ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Poorva, E-mail: vdinesh33@rediffmail.com, E-mail: vdinesh33@rediffmail.com; Kumar, Ashwini, E-mail: vdinesh33@rediffmail.com, E-mail: vdinesh33@rediffmail.com; Varshney, Dinesh, E-mail: vdinesh33@rediffmail.com, E-mail: vdinesh33@rediffmail.com [School of Physics, Vigyan Bhawan, Devi Ahilya University, Khandwa Road Campus, Indore-452001 (India)

    2014-04-24

    We report the phonon structure of Bi{sub 2}Fe{sub 4}O{sub 9} ceramics as synthesized by solid-state reaction route. Rietveld refined X-ray diffraction patterns confirmed the formation of single-phase perovskite structure and all the peaks of Bi{sub 2}Fe{sub 4}O{sub 9} perfectly indexed to the orthorhombic (space group Pbam). Raman scattering measurements identifies 12A{sub g}+1B{sub 2g}+1B{sub 3g} Raman active optical phonon modes. Apart from phonon scattering, mode at 470 cm{sup −1} is observed which is due to magnon scattering. The P-E loop infers paraelectric nature of Bi{sub 2}Fe{sub 4}O{sub 9}.

  18. Dopant rearrangement and superconductivity in Bi{sub 2}Sr{sub 2-x}La{sub x}CuO{sub 6} thin films under annealing

    Energy Technology Data Exchange (ETDEWEB)

    Cancellieri, C [EPFL, Institute of Physics of Complex Matter, LPRX, Lausanne (Switzerland); Lin, P H [EPFL, Institute of Physics of Complex Matter, LPRX, Lausanne (Switzerland); Ariosa, D [EPFL, Institute of Physics of Complex Matter, LPRX, Lausanne (Switzerland); Pavuna, D [EPFL, Institute of Physics of Complex Matter, LPRX, Lausanne (Switzerland)

    2007-06-20

    By combining x-ray diffraction (XRD), x-ray photoemission spectroscopy (XPS) and AC susceptibility measurements we investigate the evolution of structural and superconducting properties of La-doped Bi-2201 thin films grown by pulsed laser deposition (PLD) under different annealing conditions. We find that the main effect of oxygen annealing is to improve the crystal coherence by enabling La cation migration to the Sr sites. This activates the desired hole doping. Short-time Ar annealing removes the interstitial oxygen between the BiO layers, fine adjusting the effective hole doping. The superconducting critical temperature is consequently enhanced. However, longer annealings result in phase separation and segregation of the homologous compound Bi-1201. We attribute this effect to the loss of Bi during the annealing.

  19. High-Tc superconductivity in ultrathin Bi2Sr2CaCu2O(8+x) down to half-unit-cell thickness by protection with graphene.

    Science.gov (United States)

    Jiang, Da; Hu, Tao; You, Lixing; Li, Qiao; Li, Ang; Wang, Haomin; Mu, Gang; Chen, Zhiying; Zhang, Haoran; Yu, Guanghui; Zhu, Jie; Sun, Qiujuan; Lin, Chengtian; Xiao, Hong; Xie, Xiaoming; Jiang, Mianheng

    2014-12-08

    High-Tc superconductors confined to two dimension exhibit novel physical phenomena, such as superconductor-insulator transition. In the Bi2Sr2CaCu2O(8+x) (Bi2212) model system, despite extensive studies, the intrinsic superconducting properties at the thinness limit have been difficult to determine. Here, we report a method to fabricate high quality single-crystal Bi2212 films down to half-unit-cell thickness in the form of graphene/Bi2212 van der Waals heterostructure, in which sharp superconducting transitions are observed. The heterostructure also exhibits a nonlinear current-voltage characteristic due to the Dirac nature of the graphene band structure. More interestingly, although the critical temperature remains essentially the same with reduced thickness of Bi2212, the slope of the normal state T-linear resistivity varies by a factor of 4-5, and the sheet resistance increases by three orders of magnitude, indicating a surprising decoupling of the normal state resistance and superconductivity. The developed technique is versatile, applicable to investigate other two-dimensional (2D) superconducting materials.

  20. Structural, Raman, and dielectric studies on multiferroic Mn-doped Bi 1-xLax FeO 3 ceramics

    KAUST Repository

    Xing, Zhibiao

    2014-04-03

    Multiferroic Bi1-xLaxFeO3 [BLFO (x)] ceramics with x = 0.10-0.50 and Mn-doped BLFO (x = 0.30) ceramics with different doping contents (0.1-1.0 mol%) were prepared by solid-state reaction method. They were crystallized in a perovskite phase with rhombohedral symmetry. In the BLFO (x) system, a composition (x)-driven structural transformation (R3c→C222) was observed at x = 0.30. The formation of Bi2Fe 4O9 impure phase was effectively suppressed with increasing the x value, and the rhombohedral distortion in the BLFO ceramics was decreased, leading to some Raman active modes disappeared. A significant red frequency shift (~13 cm-1) of the Raman mode of 232 cm-1 in the BLFO ceramics was observed, which strongly perceived a significant destabilization in the octahedral oxygen chains, and in turn affected the local FeO6 octahedral environment. In the Mn-doped BLFO (x = 0.30) ceramics, the intensity of the Raman mode near 628 cm-1 was increased with increasing the Mn-doping content, which was resulted from an enhanced local Jahn-Teller distortions of the (Mn,Fe)O6 octahedra. Electron microscopy images revealed some changes in the ceramic grain sizes and their morphologies in the Mn-doped samples at different contents. Wedge-shaped 71° ferroelectric domains with domain walls lying on the {110} planes were observed in the BLFO (x = 0.30) ceramics, whereas in the 1.0 mol% Mn-doped BLFO (x = 0.30) samples, 71° ferroelectric domains exhibited a parallel band-shaped morphology with average domain width of 95 nm. Dielectric studies revealed that high dielectric loss of the BLFO (x = 0.30) ceramics was drastically reduced from 0.8 to 0.01 (measured @ 104 Hz) via 1.0 mol% Mn-doping. The underlying mechanisms can be understood by a charge disproportion between the Mn4+ and Fe2+ in the Mn-doped samples, where a reaction of Mn4+ + Fe2+→Mn3+ + Fe3+ is taken place, resulting in the reduction in the oxygen vacancies and a suppression of the electron hopping from Fe3+ to Fe2+ ions

  1. Structural, electrical and magneto-electric characteristics of BiMgFeCeO6 ceramics

    Science.gov (United States)

    Parida, Kalpana; Dehury, Sujit Kumar; Choudhary, R. N. P.

    2016-12-01

    The polycrystalline sample of double perovskite BiMgFeCeO6 was prepared by a standard ceramics processing technique (high-temperature solid-state reaction). Preliminary structural analysis using X-ray diffraction data has exhibited the formation of the material in orthorhombic system. Detailed studies of electrical properties (permittivity (dielectric constant), tangent loss, electrical modulus, conductivity and impedance) of the material as a function of frequency (1 kHz-1 MHz) at different temperatures (25-500 °C) have provided many interesting results on conduction mechanism, structure-properties relationship, etc. An important role of interface in getting high dielectric material has been realized. The existence of space charge polarization and Maxwell-Wagner relaxation in the material, particularly at low frequencies and high temperatures, has been observed. Nyquist plots discuss the temperature-dependent contributions of grain, grain boundary and electrode effect. The nature and existence of the hysteresis loop confirmed the ferroelectric characteristics of the material at room temperature. Study of dc conductivity of the compound with temperature exhibits presence of negative temperature coefficient of resistance (NTCR) characteristics in it. An optical energy band gap of ∼2.9 eV was determined from the UV-visible absorbance spectrum. A unique data on magneto-electric (ME) coefficient, measured by varying dc bias magnetic field, was obtained.

  2. Study of multiferroic properties of Bi2Fe2WO9 ceramic for device application

    Science.gov (United States)

    Rout, Jyoshna; Choudhary, R. N. P.

    2016-09-01

    The Bi2Fe2WO9 ceramic was prepared using a standard solid-state reaction technique. Preliminary analysis of X-ray diffraction pattern revealed the formation of single-phase compound with orthorhombic crystal symmetry. The surface morphology of the material captured using scanning electron microscope (SEM) exhibits formation of a densely packed microstructure. Comprehensive study of dielectric properties showed two anomalies at 200∘C and 450∘C: first one may be related to magnetic whereas second one may be related to ferroelectric phase transition. The field dependent magnetic study of the material shows the existence of small remnant magnetization (Mr) of 0.052emμ/g at room temperature. The existence of magneto-electric (ME) coupling coefficient along with above properties confirms multi-ferroic characteristics of the compound. Selected range temperature and frequency dependent electrical parameters (impedance, modulus, conductivity) of the compound shows that electric properties are correlated to its microstructure. Detailed studies of frequency dependence of ac conductivity suggest that the material obeys Jonscher’s universal power law.

  3. AC impedance spectroscopy and conductivity studies of Dy doped Bi4V2O11 ceramics

    Science.gov (United States)

    Bag, Sasmitarani; Das, Parthasarathi; Behera, Banarji

    2017-03-01

    The ac impedance and conductivity properties of Dy doped Bi4V2 - x Dy x O11 (x = 0.05, 0.10, 0.15 and 0.20) ceramics prepared by solid-state reaction technique, in a wide frequency range at different temperatures have been studied. All the samples exhibited β-type phase orthorhombic structure at room temperature. The Nyquist plot confirmed the presence of both grain and grain boundary effects for all Dy doped samples. Double relaxation behavior was also observed. The grain and grain boundary resistance decreases with rise in temperature for all the concentration and exhibits a typical negative temperature co-efficient of resistance (NTCR) behavior. An analysis of the electric modulus suggests the possible hopping mechanism for electrical transport processes of all the materials. The ac conductivity spectrum obeys Jonscher's universal power law. DC conductivity of the materials were also studied and values of the activation energy found to be 0.40, 0.49, 0.73 and 0.78 eV for the compositions x = 0.05, 0.10, 0.15 and 0.20, respectively, at different temperatures (150-375 °C).

  4. Pyroelectric properties and electrical conductivity in samarium doped BiFeO 3 ceramics

    KAUST Repository

    Yao, Yingbang

    2012-06-01

    Samarium (Sm 3+) doped BiFeO 3 (BFO) ceramics were prepared by a modified solid-state-reaction method which adopted a rapid heating as well as cooling during the sintering process. The pyroelectric coefficient increased from 93 to 137 μC/m 2 K as the Sm 3+ doping level increased from 1 mol% to 8 mol%. Temperature dependence of the pyroelectric coefficient showed an abrupt decrease above 80 °C in all samples, which was associated with the increase of electrical conductivity with temperature. This electrical conduction was attributed to oxygen vacancy existing in the samples. An activation energy of ∼0.7 eV for the conduction process was found to be irrespective of the Sm 3+ doping level. On the other hand, the magnetic Néel temperature (T N) decreased with increasing Sm 3+ doping level. On the basis of our results, the effects of Sm doping level on the pyroelectric and electrical properties of the BFO were revealed. © 2011 Elsevier Ltd. All rights reserved.

  5. Superconducting fluctuations in Bi2Sr2Ca2Cu3Ox thin films: Paraconductivity, excess Hall effect, and magnetoconductivity

    Science.gov (United States)

    Lang, W.; Heine, G.; Kula, W.; Sobolewski, Roman

    1995-04-01

    A detailed study of normal-state magnetotransport properties in (Bi,Pb)2Sr2Ca2Cu3Ox thin films with a zero-resistance critical temperature Tc0=105 K prepared by dc-magnetron sputtering on MgO substrates is reported. Measurements of the electrical resistivity, the magnetoresistance, and the Hall effect are analyzed with regard to contributions of the superconducting order-parameter thermodynamic fluctuations, using theories for two-dimensional, layered superconductors. We have obtained a consistent set of parameters, i.e., the in-plane coherence length ξab(0)=1.6 nm, the out-of-plane coherence length ξc(0)=0.14 nm, and the electron-hole asymmetry parameter β=-0.38. At temperatures below 118 K, we observe a remarkable enhancement (above theoretical predictions) of both the excess Hall effect and magnetoconductivity, whereas no such effect is detected for the zero-field paraconductivity. The above anomalies are attributed to a nonuniform critical temperature distribution inside our samples and can be well explained assuming a Gaussian distribution of Tc's with a standard deviation δTc=2.3 K. The excess Hall effect caused by superconducting fluctuations is negative in the entire accessible temperature range, which indicates, together with the paraconductivity and magnetoconductivity results that the indirect (Maki-Thompson) fluctuation process for (Bi,Pb)2Sr2Ca2Cu3Ox is vanishingly small at temperatures from Tc to 130 K.

  6. Characterization of Bi2/3Cu3Ti4O12 ceramics synthesized by semi-wet route

    Directory of Open Access Journals (Sweden)

    Pooja Gautam

    2016-12-01

    Full Text Available Bi2/3Cu3Ti4O12 (BCTO ceramic was synthesized by the semi-wet route using metal nitrate solutions and solid TiO2 powder in a stoichiometric ratio. Fourier transform infrared (FTIR study of BCTO precursor powder and calcined ceramic showed the presence of alcoholic functional groups and the stretching band of Ti-O and Cu-O respectively. X-ray diffraction (XRD, scanning electron microscope (SEM and energy dispersive x-ray spectroscopy (EDX were employed to characterize the structure, surface morphology and purity of the sintered BCTO ceramic respectively. X-ray diffraction study confirmed the single phase formation of BCTO ceramic at 1073 K. The average dimension of grains calculated by SEM and AFM was found to be in the range of 0.73±0.2 µm with clear grain boundaries. Magnetic property was investigated over a wide temperature range 2–300 K at a magnetic field of 7 tesla. The Curie temperature was calculated by zero field cooled (MZFC and field cooled (MFC magnetization at 100 Oe applied field which was found to be 125 K. The sintered BCTO ceramic shows high dielectric constant (ε'=2.9×104 at 323 K and 100 Hz.

  7. Magnetic and superconducting phase diagram of the half-Heusler topological semimetal HoPdBi

    NARCIS (Netherlands)

    Nikitin, A.M.; Pan, Y.; Mao, X.; Jehee, R.; Araizi, G.K.; Huang, Y.K.; Paulsen, C.; Wu, S.C.; Yan, B.H.; de Visser, A.

    2015-01-01

    We report a study of the magnetic and electronic properties of the non-centrosymmetric half-Heusler antiferromagnet HoPdBi (T-N = 2.0 K). Magnetotransport measurements show HoPdBi has a semimetallic behavior with a carrier concentration n= 3.7 x 10(18) cm(-3) extracted from the Shubnikov-de Haas eff

  8. Nanostructures of Sr2+ doped BiFeO3 multifunctional ceramics with tunable photoluminescence and magnetic properties.

    Science.gov (United States)

    Mandal, S K; Rakshit, T; Ray, S K; Mishra, S K; Krishna, P S R; Chandra, Amreesh

    2013-02-06

    Careful tuning of formation (calcination) temperature of Sr(2+) doped BiFeO(3) multiferroic ceramics results in tailorable particle morphologies ranging from spherical to pillar-like. Based on the minimization of Gibb's free energy approach, the dominant homogeneous mechanism for particle growth is suggested. The chemical substitution of a trivalent ion (Bi(3+)) by a divalent ion (Sr(2+)) causes the transformation of certain fraction of Fe(3+) to Fe(4+) and/or the appearance of oxygen vacancies. This has been respectively proved by the analysis of XPS and refinement of neutron diffraction data. Although significant modification in the particle morphology is observed, the crystal unit cell remains rhombohedral with a R3c space group but interesting variations in physical properties are achieved. O-vacancies induced strong and sharp photoluminescence activity in the IR region, similar to ZnO, is reported for the first time. This observation opens up a new application for multiferroic ceramics. SQUID M-H data confirms the straightening of the canted spin structure of BiFeO(3), which in turn results in magnetism similar to ferromagnetic materials. Findings of the magneto-dielectric effect are also discussed to claim the multiferroic nature of the sample.

  9. Mechanical and physical properties of Bi-2223 and Nb3Sn superconducting materials between 300 K and 7 K

    Science.gov (United States)

    Nyilas, Arman; Osamura, Kozo; Sugano, Michinaka

    2003-09-01

    Within the framework of IEC/TC90-WG5 and VAMAS/TWA16, superconducting (SC) materials are investigated with respect to their mechanical properties between 300 K and 7 K. Besides the mechanical tests, physical and electrical properties are also determined for high Tc SC-tapes. The mechanical tests comprised the characterization of tensile properties at ambient temperature as well as at 7 K of Nb3Sn-reacted strands, Bi2223 tapes, pure silver tapes, silver bars, silver alloy tapes and bare filaments extracted from Bi-2223 tapes. All these investigations are carried out using a variable temperature helium gas flow cryostat equipped with a servo hydraulic tensile machine (MTS, model 810). For the load measurements specially developed, highly sensitive cryogenic proof in situ working load cells are used. For the strain determination of the wires, a high resolution ultra-light double extensometer system with a specially developed low noise signal conditioner is used. The engineering parameters such as yield strength and elastic modulus are evaluated using the obtained data with newly developed software. For the tiny and brittle filaments load versus displacement data are obtained. A determined master line (Young's modulus versus machine compliance) established by thin 0.125 mm Ø wires of different pure metals is used for the Young's modulus estimation of filaments. For the 4 K electrical voltage-current measurements under magnetic fields of up to 13 T, an existing test facility is used for the high Tc tapes. No dependency between applied strain up to 0.3% and the critical current under magnetic field could be observed for the selected specific Bi-2223 tapes. In addition, thermal expansion curves of Bi-2223 tapes along with pure silver and silver alloy (AgMg) are determined between 290 K and 7 K using in situ working extensometers. The coefficient of thermal expansion is evaluated by the determined thermal expansion versus temperature curve.

  10. Pressure-induced superconductivity in the giant Rashba system BiTeI

    OpenAIRE

    VanGennep, D.; Linscheid, A.; Jackson, D E; Weir, S. T.; Vohra, Y. K.; Berger, H.; Stewart, G. R.; Hennig, R. G.; Hirschfeld, P. J.; Hamlin, J. J.

    2016-01-01

    At ambient pressure, BiTeI is the first material found to exhibit a giant Rashba splitting of the bulk electronic bands. At low pressures, BiTeI undergoes a transition from trivial insulator to topological insulator. At still higher pressures, two structural transitions are known to occur. We have carried out a series of electrical resistivity and AC magnetic susceptibility measurements on BiTeI at pressure up to ~40 GPa in an effort to characterize the properties of the high-pressure phases....

  11. Synthesis and Microstructure of Partly-oriented Bismuth Layer Structure Ferroelectrics Ceramics SrBi4Ti4O15

    Institute of Scientific and Technical Information of China (English)

    HAO Hua; LIU Hanxing; OUYANG Shixi

    2005-01-01

    SrBi4Ti4O15 powder was synthesized by conventional solid state synthesis (CS) and molten salt synthesis (MSS). MSS method can synthesize plate-like SrBi4Ti4O15 at lower temperature ( 900℃ ) than CS method. Plate- like form becomes more distinct when the synthesis temperature increases. This would help cause the grain orientation of the ceramics after sintering. The sintered samples of MSS had grain orientation at (0,0,10) plane. The degree of (0,0,10) grain orientation F was 62.1%. Hot pressing made (0,0,10) grain orientation more distinct ( F = 85.7% ). The microstructures of the sintered samples were detected by SEM. Due to the grain orientation, the density of samples fabricated by MSS was lower than that of prepared by CS.

  12. Relationships between oxygen content, modulation period and superconducting property of Bi-based superconducting oxides. Bi kei sankabtsu chodendotai ni okeru sanso ganryo, hencho kozo oyobi chodendo tokusei no sokan

    Energy Technology Data Exchange (ETDEWEB)

    Deshimaru, Y.; Shimizu, Y.; Miura, N.; Yamazoe, N. (Kyushu Univ., Fukuoka (Japan). Graduate School of Engineering Sciences); Hiroi, Z.; Bando, Y. (Kyoto Univ., Kyoto (Japan). Inst. for Chemical Research)

    1992-09-10

    Two (2223 and 2212) of three superconducting phases in the Pb-doped Bi-Sr-Ca-Cu-O (BSCCO) oxide superconductor were examined for their changes of crystal structures and superconducting properties with changing oxygen content. Their oxygen sorption behavior examined by the temperature-programmed-desorption method showed that both samples desorb trace amounts of oxygen in a temperature range of 350-600 centigrade and the behavior examined by the temperature-programmed oxidation method showed that they absorb (absorb) reversibly oxygen desorbed above in a range of 100-350 centigrade. The critical temperature to bear diamagnetism (Tc) of the 2223 sample fell from 111 K to 96 K as oxygen was desorbed up to 600 centigrade. However, Tc recovers reversibly to the initial value when oxygen was re-absorbed. Contrary to the 2223, the 2212 sample showed the opposite Tc change. Both samples increased in their c-axes lengths and their modulation periods and the changes were reversible respectively. It was pointed out that the Tc behaviors of both sample systems were dependent on the concentration of holes on the CuO2 surfaces. 33 refs., 9 figs.

  13. Inductance mode characteristics of a ceramic YBa2Cu3O7-x radio-frequency superconducting quantum interference device at 77 K

    DEFF Research Database (Denmark)

    Il'ichev, E. V.; Andreev, A. V.; Jacobsen, Claus Schelde

    1993-01-01

    Experimental results on some radio-frequency superconducting quantum interference device (rf-SQUID) signal properties are presented. The quantum interferometer was made of ceramic YBa2Cu3O7−x and was due to a low critical current operated in the inductance or nonhysteretic mode. With bias current...

  14. Magnetic studies of multiferroic Bi(1-x)Sm(x)FeO(3) ceramics synthesized by mechanical activation assisted processes.

    Science.gov (United States)

    Maurya, Deepam; Thota, Harikishan; Garg, Ashish; Pandey, Brajesh; Chand, Prem; Verma, H C

    2009-01-14

    Bi(1-x)Sm(x)FeO(3) (x = 0.0-0.2) ceramic samples were prepared by mechanical activation assisted solid-state-reaction synthesis. A stoichiometric mixture of Bi(2)O(3), Sm(2)O(3), and Fe(2)O(3) powders was mechanically milled and this was followed by heat treatment at 700 °C for 1 h. Room temperature x-ray diffraction patterns confirmed the formation of perovskite structured Bi(1-x)Sm(x)FeO(3) phase. Vibrating sample magnetometry measurements showed that to a certain extent, Sm doping of BiFeO(3) leads to increased magnetization and a sharp magnetic transition at ∼380 °C. Mössbauer spectroscopy confirmed the presence of single-phase material for the doped compositions whereas electron paramagnetic resonance analysis showed the effect of doping on the variation in the degree of canting in the samples. At doping levels of 10 at.% Sm, the improvement in the magnetic behaviour appears to arise from a combination of the propensity of the samples to form pure phase material, partial destruction of spin cycloids, increased canting of spins and interaction between magnetic ions.

  15. Anisotropic thermal transport in Bi2223/Ag superconducting tape with sandwiched structure

    Energy Technology Data Exchange (ETDEWEB)

    Naito, Tomoyuki, E-mail: tnaito@iwate-u.ac.jp [Department of Materials Science and Engineering, Faculty of Engineering, Iwate University, Morioka 020-8551 (Japan); Soft-Path Engineering Research Center (SPERC), Faculty of Engineering, Iwate University, Morioka 020-8551 (Japan); Fujishiro, Hiroyuki [Department of Materials Science and Engineering, Faculty of Engineering, Iwate University, Morioka 020-8551 (Japan); Soft-Path Engineering Research Center (SPERC), Faculty of Engineering, Iwate University, Morioka 020-8551 (Japan); Osabe, Goro; Fujikami, Jun [Sumitomo Electric Industries Ltd., Osaka 554-0024 (Japan)

    2013-01-15

    Highlights: ► Anisotropic thermal conductivity of the Bi2223/Ag tape was measured. ► Thermal conductivity was analyzed using an equivalent heat current circuit. ► Thermal transports along the length and width directions were nearly the same. -- Abstract: The thermal conductivity, κ(T), of the Bi2223/Ag tape reinforced by metal tapes (stainless steel (SS) or copper-based alloy (CA)) from both side was evaluated along the length (l) and width (w) directions. κ(T) along the l-direction was measured directly using a single tape and that along the w-direction was estimated from the κ(T) measured for a stacked bundle which consists of several sandwiched Bi2223/Ag tapes. We analyzed the obtained κ(T) curves using an equivalent heat current circuit, and found that the heat transports along both directions were nearly the same and that the route of heat-flow depended on the species of the reinforcing metal. The absolute values of κ(T) at 77 K along the l- and w- directions for the Bi2223/Ag-SS tape were 174 and 140 W m{sup −1} K{sup −1} and those for the Bi2223/Ag-CA tape were 206 and 206 W m{sup −1} K{sup −1}, respectively, the values of which were approximately 30–40% and 10–15% smaller than those of the standard Bi2223/Ag tape.

  16. Oxygen Adsorption-Desorption Behavior and Superconducting Properties of High-Tc Bi(Pb)-Sr-Ca-Cu-O

    Science.gov (United States)

    Miura, Norio; Suzuta, Hiroki; Deshimaru, Yuichi; Shimizu, Youichi; Sakashita, Hirofumi; Yamazoe, Noboru

    1989-07-01

    Temperature-programmed desorption (TPD) chromatograms revealed that a small amount of oxygen was desorbed from high-Tc Bi(Pb)-Sr-Ca-Cu-O (BPSCCO) in the temperature range from ca. 350 to ca. 650°C prior to a steep increase of oxygen desorption in the higher temperature range. The Tc of BPSCCO was significantly lowered with the progress of oxygen desorption especially in the former temperature range, and was restored to the original level when the desorbed oxygen was recovered. With no corresponding changes in X-ray powder diffraction pattern being detected, the oxygen desorbed below ca. 650°C was concluded to have strong relevance to the superconductivity of BPSCCO.

  17. Size effect of strong-coupled superconducting In{sub 2}Bi nanoparticles: An investigation of short-range electron phonon coupling

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Po-Yu; Gandhi, Ashish Chhaganlal; Wu, Sheng Yun, E-mail: sywu@mail.ndhu.edu.tw [Department of Physics, National Dong Hwa University, Hualien 97401, Taiwan (China)

    2015-05-07

    We report the influence of the nanosized effect on the superconducting properties of bimetallic In{sub 2}Bi nanoparticles. In this study, the temperature- and applied magnetic field-dependence of the magnetization were utilized to investigate the electron-phonon coupling effect while controlling particle sizes 〈d〉 from 21(2) to 42(5) nm. As the particle size decreases, the electron-phonon constant λ{sub EP} decreases rapidly, signaling the short-range electron-phonon coupling effect which acts to confine the electrons within a smaller volume, thereby giving rise to a higher superconducting transition temperature T{sub C}. An enhanced superconducting transition was observed from the temperature dependence of magnetization, revealing a main diamagnetic Meissner state below T{sub C} ∼ 5.72(5) K for 〈d〉 = 31(1) nm In{sub 2}Bi nanoparticles. The variation of the T{sub C} is very sensitive to the particle size, which might be due to crystallinity and size uniformity of the samples. The electron-phonon coupling to low lying phonons is found to be the leading mechanism for the observed strong-coupling superconductivity in the In{sub 2}Bi system.

  18. Composition-driven structural phase transitions in rare-earth-doped BiFeO3 ceramics: a review.

    Science.gov (United States)

    Arnold, Donna C

    2015-01-01

    Bismuth ferrite suffers from high leakage currents and the presence of a complex incommensurate spin cycloidal magnetic ordering, which has limited its commercial viability and has led researchers to investigate the functionality of doped BiFeO3 ceramics. In particular, the substitution of rare earths onto the Bi(3+) site of the perovskite lattice have been shown to lead to improved functional properties, including lower leakage currents and the suppression of the magnetic spin cycloid. There is particular interest in materials with compositions close to structural morphotropic phase boundaries, because these may lead to materials with enhanced electronic and magnetic properties analogous to the highly relevant PbZrO3- PbTiO3 solid solution. However, many contradictory crystal structures and physical behaviors are reported within the literature. To understand the structure-property relationships in these materials, it is vital that we first unravel the complex structural phase diagrams. We report here a comprehensive review of structural phase transitions in rare-earth-doped bismuth ferrite ceramics across the entire lanthanide series. We attempt to rationalize the literature in terms of the perovskite tool kit and propose an updated phase diagram based on an interpretation of the literature.

  19. Multiferroic properties in Zn and Ni co-doped BiFeO{sub 3} ceramics by solution combustion method (SCM)

    Energy Technology Data Exchange (ETDEWEB)

    Chaudhari, Y.A., E-mail: yogeshchaudhari2007@yahoo.com [Department of Physics, School of Physical Sciences, North Maharashtra University, Jalgaon 425 001, Maharashtra (India); Department of Engineering Sciences and Humanities (DESH), SRTTC - FOE, Pune 410 405, Maharashtra (India); Singh, A. [Magnetics and Advanced Ceramics Laboratory, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110 016 (India); Mahajan, C.M. [Department of Engineering Sciences and Humanities (DESH), Vishwakarma Institute of Technology, Pune 411 037, Maharashtra (India); Jagtap, P.P.; Abuassaj, E.M. [Department of Physics, School of Physical Sciences, North Maharashtra University, Jalgaon 425 001, Maharashtra (India); Chatterjee, R. [Magnetics and Advanced Ceramics Laboratory, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110 016 (India); Bendre, S.T., E-mail: bendrest@gmail.com [Department of Physics, School of Physical Sciences, North Maharashtra University, Jalgaon 425 001, Maharashtra (India)

    2013-12-15

    In present paper, we synthesize the multiferroic Bi{sub 1−x}Zn{sub x}Fe{sub 1−y}Ni{sub y}O{sub 3} (x=y=0.025, 0.05, 0.075 and 0.1) ceramics by using solution combustion method (SCM). The room temperature ferroelectric and magnetic hysteresis loops present the co-existence of magnetism and ferroelectricity in a single phase. This ferroelectric hysteresis loops exhibit an unsaturated behavior and represents a partial reversal of polarization at room temperature. Beside, this it was found that the room temperature magnetization measurement is giving rise to the appearance of weak ferromagnetism. The Bi{sub 0.975}Zn{sub 0.025}Fe{sub 0.975}Ni{sub 0.025}O{sub 3} and Bi{sub 0.9}Zn{sub 0.1}Fe{sub 0.9}Ni{sub 0.1}O{sub 3} ceramics display the clear evidence of dielectric anomaly around 300 and 325 °C which corresponds to antiferromagnetic to paramagnetic phase transition of BiFeO{sub 3} ceramics. The structural study shows the Bi{sub 1−x}Zn{sub x}Fe{sub 1−y}Ni{sub y}O{sub 3} (x=y=0.025, 0.05, 0.075 and 0.1) ceramics have rhombhohedral perovskite structure. The surface morphology of the samples was examined by SEM. - Highlights: • Bi{sub 1−x}Zn{sub x}Fe{sub 1−y}Ni{sub y}O{sub 3} multiferroic ceramics. • Solution Combustion Method (SCM). • Ferroelectric, dielectric and magnetic properties. • To make high temperature synthesized Bi{sub 1−x}Zn{sub x}Fe{sub 1−y}Ni{sub y}O{sub 3} multiferroic ceramics. • First time we have synthesized the Bi{sub 1−x}Zn{sub x}Fe{sub 1−y}Ni{sub y}O{sub 3} ceramics by solution combustion method.

  20. Synthesis and microstructural evolution of BiFeO{sub 3} ceramics modified with ZnO; Sintesis y evolucion microestructural de ceramicas de BiFeO{sub 3} modificadas con ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Bernandrdo, M. S.; Ardiel, T.; Villegas, M.

    2010-07-01

    BiFeO{sub 3} ceramic materials have received a great interest in the last years due to their potential application as multiferroic devices. However, the preparation of BiFeO{sub 3}-based bulk ceramics shows serious difficulties related to the presence of secondary phases and the densification process. These problems result in a high electrical conductivity which up to now limits the technological applications of BiFeO{sub 3}. However, it has been observed experimentally that the conductivity in these ceramics can be reduced by acting on their microstructure. In this framework, the present contribution is focused on the analysis of the microstructural changes promoted by superficial doping of the BiFeO{sub 3} ceramic particles with ZnO. The structural and microstructural characterization of the obtained materials reveals that the addition of ZnO results in a solutedrag effect. Due to this effect the dopant remains segregated at the grain boundaries so inhibiting the grain growth during sintering. (Author)

  1. Quantitative description of the phase transition of Aurivillius oxides Sm modified BaBi{sub 4}Ti{sub 4}O{sub 15} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Pinyang, E-mail: fpy_2000@163.com [College of Physics and Information Technology, Shaanxi Normal University, Xi' an 710062 (China); Shaanxi Key Laboratory of Photoelectric Functional Materials and Devices, School of Materials and Chemical Engineering, Xi' an Technological University, Xi' an 710032 (China); Liu, Peng [College of Physics and Information Technology, Shaanxi Normal University, Xi' an 710062 (China); Xi, Zengzhe [Shaanxi Key Laboratory of Photoelectric Functional Materials and Devices, School of Materials and Chemical Engineering, Xi' an Technological University, Xi' an 710032 (China)

    2015-07-15

    BaBi{sub 4}Ti{sub 4}O{sub 15}+xwt.%Sm{sub 2}O{sub 3} (x=0.00, 0.25, 0.50, 0.75) ceramics were prepared by the solid-state reaction method. The effect of samarium additives on the structural and electrical properties of BBT ceramic was investigated. XRD patterns indicate that all ceramics are an m=4 members of Aurivillius oxides and no secondary phases were detected. A broad dielectric peak in frequency dependent dielectric spectrum is observed during the phase transition of all the BBT ceramics. The modified Curie–Weiss law, Vogel–Fucher relationship and Lorentz-type law were used to describe the phase transition behavior. The relaxor behavior was described well by the modified Curie–Weiss law and Vogel–Fucher relation. The effect of samarium additives on the degree of relaxation and diffuseness of BBT ceramics was discussed.

  2. Influence Of Thermal Treatment On Relaxor Properties Of BaBi2Nb2O9 Ceramics

    Directory of Open Access Journals (Sweden)

    Adamczyk M.

    2015-06-01

    Full Text Available In the hereby paper the implications of thermal modification of BaBi2Nb2O9 ceramics in high vacuum (5×10−11 bar at a temperature equal of 1173K are widely discussed. The mentioned modification caused changes in the ions concentration (confirmed by EDS and XPS analysis and as a consequence an influence on the value of the unit cell parameters as well as on the dielectric and relaxor properties of described ceramics. The obtained results of EDS and XPS analysis of the sample before and after thermal treatment revealed bismuth ions diffusion to the surface of the sample (which was expected and an almost complete the lack of barium ions on the modified surface. The comparison of EDS and XPS analysis results, suggested that they penetrated the interior of the sample and embedded into the crystal structure in place of bismuth. The hypothesis is in good agreement with the results of X-ray diffraction – the volume of the unit cell had an insignificant increase. The changes in the ions concentration influenced, also in a distinct manner, the dielectric and relaxor properties as well as on the shape of temperature characteristic of thermal stimulated depolarization current observed in BBN ceramics.

  3. Improved electrical characteristics of Pr-doped BiFeO3 ceramics prepared by sol-gel route

    Science.gov (United States)

    Madolappa, Shivanand; Kundu, Swarup; Bhimireddi, Rajasekhar; Varma, K. B. R.

    2016-06-01

    Ceramics of Bi1-x Pr x FeO3 (x = 0-0.1) were fabricated using the nanocrystalline powders obtained via sol-gel route. X-ray powder diffraction studies confirmed that these belonged to rhombohedral perovskite structure associated with R3c space group. The dielectric properties of the ceramic samples as a function of frequency (100 Hz-10 MHz) and temperature (30 °C-250 °C) were studied. The dielectric constant increased while the loss decreased with the increase of Pr content. Dielectric dispersion in these samples was found to be poly dispersive Debye type relaxation as confirmed by invoking Cole-Cole relation. Impedance spectroscopy was employed to determine the electrical parameters associated with the grain and grain boundaries. Grain and grain boundary resistances were found to decrease with the increase of temperature for all the samples under study. The activation energies for the dielectric relaxation were evaluated by electric modulus spectra and these increase with the increase of Pr dopant level. The frequency dependent conductivity at various temperatures demonstrated the involvement of correlated barrier hopping conduction mechanism. The electrical conduction in these ceramics was ascribed to long and short range migration of oxygen ion vacancies as demonstrated by temperature dependent ac conductivity studies.

  4. Improved ferroelectric and pyroelectric properties of Pb-doped SrBi{sub 4}Ti{sub 4}O{sub 15} ceramics for high temperature applications

    Energy Technology Data Exchange (ETDEWEB)

    Venkata Ramana, E., E-mail: venkataramanaesk@rediffmail.com [I3N-Aveiro, Department of Physics, University of Aveiro, Aveiro 3810 193 (Portugal); Graça, M.P.F.; Valente, M.A. [I3N-Aveiro, Department of Physics, University of Aveiro, Aveiro 3810 193 (Portugal); Bhima Sankaram, T. [Materials Research Laboratory, Department of Physics, Osmania University, Hyderabad 500 007 (India)

    2014-01-15

    Highlights: • Sr{sub 1−x}Pb{sub x}Bi{sub 4}Ti{sub 4}O{sub 15} (SPBT, x = 0 − 0.4) ceramics were synthesized by soft chemical method. • X-ray diffraction analysis confirmed the formation of bismuth layered structure. • SEM images showed plate like grain morphology with random orientation of plate faces. • Pb-doping resulted in improved ferroelectricity of SrBi{sub 4}Ti{sub 4}O{sub 15} ceramics. • Pb-doped SrBi{sub 4}Ti{sub 4}O{sub 15} exhibited improved pyroelectric properties with high T{sub C}. -- Abstract: Ferroelectric properties of Pb-modified strontium bismuth titanate ceramics with chemical formula Sr{sub 1−x}Pb{sub x}Bi{sub 4}Ti{sub 4}O{sub 15} (x = 0–0.4) were investigated. Polycrystalline ceramics were synthesized by soft chemical method to study the effect of Pb-doping on its physical properties. X-ray diffraction analysis revealed a bismuth layered structure for all the compounds. The doping resulted in an increased tetragonal strain and improved ferroelectric properties. Scanning electron microscope images showed plate like grain morphology with random orientation of platelets. The ferroelectric transition temperature of the ceramics increased systematically from 525 °C to 560 °C with the increase of doping concentration. The piezoelectric coefficient (d{sub 33}) of the ceramics was enhanced significantly with Pb doping, exhibiting a maximum value of 21.8 pC/N for 40 mol.% Pb-doped SBT. Pyroelectric studies carried out using the Byer–Roundy method indicated that the modified SBT ceramics are promising candidates for high temperature pyroelectric applications.

  5. Structural, magnetic and magnetoelectric properties of single phase La3+ and Er3+ co-doped Bi0.85-x La0.15Er x FeO3 (0 ≤ x ≤ 0.1) ceramics

    Science.gov (United States)

    Manjusha; Yadav, K. L.; Mall, Ashish Kumar

    2016-11-01

    A sol-gel reaction method is used to prepare La3+ and Er3+ co-doped ceramic Bi0.85-x La0.15Er x FeO3 (x = 0, 0.05, 0.07 and 0.10) equivalently denoted as BLEFO. Bi0.85-x La0.15Er x FeO3 exhibits the structural transition from rhombohedral to a triclinic structure with quite small triclinic distortion; as confirmed by the Rietveld refinement analysis. Field emission scanning electron micrographs reveal the presence of interconnected spherical grains. From transmission electron microscopy, the average crystal size was found to be 60-65 nm. Co-doping with La and Er enhanced the magnetic properties such as saturation magnetization and magnetic moment of BiFeO3 as confirmed by vibrating sample magnetometer at 300 K and as well as by superconducting quantum interference device (SQUID) analysis at 5 K. An unusual behavior has been observed in BLEFO at 300 K, because it shows the weak ferromagnetic behavior besides its antiferromagnetic nature at room temperature. An irreversibility effect and a large bifurcation have been observed below room temperature in BLEFO in SQUID measurement. The value of magnetoelectric (ME) coupling coefficient increases from 2.60 (x = 0) to 6.58 (x = 0.10) mV cm-1-Oe at 3500 Oe. A negative temperature coefficient of the resistance behavior analogous to a semiconductor is confirmed by the impedance analysis. The enhanced multiferroic properties are attributed to the enhanced ME interaction, which results from the La and Er substitution at A site of BiFeO3.

  6. Structure, electrical properties of Bi(Fe, Co)O3-BaTiO3 piezoelectric ceramics with improved Curie temperature

    Science.gov (United States)

    Zhou, Changrong; Cen, Zhenyong; Yang, Huabin; Zhou, Qin; Li, Weizhou; Yuan, Changlai; Wang, Hua

    2013-02-01

    Dense (1-y)BiFe1-xCoxO3-yBaTiO3 (BFC-BTx, y=0.29, x=0-0.012) high-temperature lead-free ceramics were prepared by the conventional oxide-mixed method and the effects of BiCoO3 modification on microstructural, electrical properties and their Curie temperatures were investigated. The solid solutions show a single phase perovskite structure, and the content of BiCoO3 has a significant effect on the microstructure of ceramics. The BFC-BTx ceramics exhibit improved Curie temperature Tc, together with increased piezoelectric properties. In particular, x=0.6% BFC-BTx ceramics, with a Curie temperature, Tc, of ∼488 °C, show optimum piezoelectric properties of d33=167 pC/N, kp=0.32. The combination of good piezoelectric properties and high Tc makes these ceramics suitable for elevated temperature piezoelectric devices.

  7. Structure, electrical properties of Bi(Fe, Co)O{sub 3}-BaTiO{sub 3} piezoelectric ceramics with improved Curie temperature

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Changrong, E-mail: zcr750320@yahoo.com.cn [School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin, Guangxi 541004 (China); Cen Zhenyong [School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin, Guangxi 541004 (China); Yang Huabin [School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin, Guangxi 541004 (China); School of Materials Science and Engineering, Central South University, Changsha, Hunan 410083 (China); Zhou Qin [School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin, Guangxi 541004 (China); Li Weizhou [School of Materials Science and Engineering, Guangxi University, Nanning, Guangxi 530004 (China); Yuan Changlai; Wang Hua [School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin, Guangxi 541004 (China)

    2013-02-01

    Dense (1-y)BiFe{sub 1-x}Co{sub x}O{sub 3}-yBaTiO{sub 3} (BFC-BTx, y=0.29, x=0-0.012) high-temperature lead-free ceramics were prepared by the conventional oxide-mixed method and the effects of BiCoO{sub 3} modification on microstructural, electrical properties and their Curie temperatures were investigated. The solid solutions show a single phase perovskite structure, and the content of BiCoO{sub 3} has a significant effect on the microstructure of ceramics. The BFC-BTx ceramics exhibit improved Curie temperature T{sub c}, together with increased piezoelectric properties. In particular, x=0.6% BFC-BTx ceramics, with a Curie temperature, T{sub c}, of {approx}488 Degree-Sign C, show optimum piezoelectric properties of d{sub 33}=167 pC/N, k{sub p}=0.32. The combination of good piezoelectric properties and high T{sub c} makes these ceramics suitable for elevated temperature piezoelectric devices.

  8. Electron-phonon coupling in superconducting β-PdBi{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Ramesh [Dept. of Physics, Feroze Gandhi Institute of Engineering and Technology, Raebareli-229001 (India); Dwivedi, Shalini; Sharma, Yamini, E-mail: sharma.yamini62@gmail.com [Theoretical Condensed Matter Physics Laboratory, Dept. of Physics, Feroze Gandhi College, Raebareli-229001 (India)

    2015-06-24

    We have studied the electronic, transport and vibrational properties of low temperature superconductor β-PdBi{sub 2}. The band manifold clearly demonstrates the 2D-layered structure with multiple gaps. The intersection of bands at E{sub F} in the Γ-P, Γ-N directions gives rise to complicated Fermi surface topology, which contains quite complicated multiple connected sheets, as well as hole and electron-like pockets. From the low temperature specific heat, we have estimated the electron-phonon coupling constant λ{sub el-ph} which has a very high value of 3.66. The vibrational properties clearly illustrates that the strong coupling makes the lattice unstable. The calculated properties confirm that β-PdBi{sub 2} is an intermediate coupling superconductor.

  9. Improved multiferroic properties of La-doped 0.6BiFeO3-0.4SrTiO3 solid solution ceramics

    Institute of Scientific and Technical Information of China (English)

    Ma Zheng-Zheng; Li Jian-Qing; Tian Zhao-Ming; Qiu Yang; Yuan Song-Liu

    2012-01-01

    The 0.6(Bi1-xLax)FeO3-0.4SrTiO3 (x =0,0.1) multiferroic ceramics are prepared by a modified Pechini method to study the effect of substitution of SrTiO3 and La in BiFeO3.The X-ray diffraction patterns confirm the single phase characteristics of all the compositions each with a rhombohedral structure. The magnetic properties of the ceramics are significantly improved by a solid solution with SrTiO3 and substitution of La.The values of the dielectric constant εr and loss tangent tan δ of all the samples decrease with increasing frequency and become constant at room temperature.The La-doped 0.6BiFeO3-0.4SrTiO3 ceramics exhibit improved dielectric and ferroelectric properties,with higher dielectric constant enhanced remnant polarization (Pr) and lower leakage current at room temperature.Compared with a anti-ferromagnetic BiFeO3 compound,the 0.6(Bi0.9La0.1)FeO3-0.4SrTiO3 sample shows the optimal ferromagnetism with remnant magnetization Mr ~ 0.135 emμ/g and ferroelectricity with Pr ~ 5.94 μC/cm2 at room temperature.

  10. Structure and Magnetic Properties of Bi5Ti3FeO15 Ceramics Prepared by Sintering, Mechanical Activation and Edamm Process. A Comparative Study

    Directory of Open Access Journals (Sweden)

    Jartych E.

    2016-06-01

    Full Text Available Three different methods were used to obtain Bi5Ti3FeO15 ceramics, i.e. solid-state sintering, mechanical activation (MA with subsequent thermal treatment, and electrical discharge assisted mechanical milling (EDAMM. The structure and magnetic properties of produced Bi5Ti3FeO15 samples were characterized using X-ray diffraction and Mössbauer spectroscopy. The purest Bi5Ti3FeO15 ceramics was obtained by standard solid-state sintering method. Mechanical milling methods are attractive because the Bi5Ti3FeO15 compound may be formed at lower temperature or without subsequent thermal treatment. In the case of EDAMM process also the time of processing is significantly shorter in comparison with solid-state sintering method. As revealed by Mössbauer spectroscopy, at room temperature the Bi5Ti3FeO15 ceramics produced by various methods is in paramagnetic state.

  11. Resonant Raman scattering in superconducting Ba1-xKxBiO3

    NARCIS (Netherlands)

    Menushenkov, AP; Troyan, IA; Eremets, MI

    2003-01-01

    The effect of the photon energy of the exciting laser radiation on the Raman spectra of Ba1 - xKxBiO3 with x = 0.25, 0.40, and 0.50 is studied. An increase in the laser wavelength from 488 to 750 nm scarcely affects the amplitudes and frequencies of the spectral lines in the Raman spectra of the non

  12. Switchable Ferroelectric Diode Effect and Piezoelectric Properties of Bi0.9La0.1FeO3 Ceramics

    Institute of Scientific and Technical Information of China (English)

    GONG Yu-Fei; WU Ping; LIU Wei-Fang; WANG Shou-Yu; LIU Guang-Yao; RAO Guang-Hui

    2012-01-01

    Multiferroic ceramics Bi0.9La0.1FeO3 are synthesized by solid-state reactions and sintered at various temperatures. The rhombohedral structure with the space group R3c is confirmed by means of x-ray diffraction, and their multiferroic properties are investigated. Bi0.9La0.1FeO3 ceramics sintered at 880°C are found to have the lowest leakage current density and the largest saturated polarization among all the samples. A diode-like current-voltage hysteresis that could be switched by an external voltage is observed in the Bi0.9La0.1FeO3 ceramics. A typical "butterfly" shaped strain-versus-voltage curve is shown with a maximum strain of 0.09% at 7kV. Room-temperature magnetization exhibits a hysteresis loop, indicating that the modulation of the spin structure of BiFeO3 has been suppressed.%Multiferroic ceramics Bi0.9La0.1FeO3 are synthesized by solid-state reactions and sintered at various temperatures.The rhombohedral structure with the space group R3c is confirmed by means of x-ray diffraction,and their multiferroic properties are investigated.Bi0.9La0.1 FeO3 ceramics sintered at 880℃ are found to have the lowest leakage current density and the largest saturated polarization among all the samples.A diode-like currentvoltage hysteresis that could be switched by an external voltage is observed in the Bi0.9La0.1 FeO3 ceramics.A typical “butterfly” shaped strain-versus-voltage curve is shown with a maximum strain of 0.09%o at 7kV.Roomtemperature magnetization exhibits a hysteresis loop,indicating that the modulation of the spin structure of BiFeOa has been suppressed.

  13. BiFeO3-doped (Na0.5K0.5NbO3 lead-free piezoelectric ceramics

    Directory of Open Access Journals (Sweden)

    Xueyi Sun et al

    2008-01-01

    Full Text Available Lead-free piezoelectric ceramics (1−x(Na0.5K0.5NbO3-xBiFeO3 (x=0~0.07 were synthesized by the solid-state reaction. Differential scanning calorimetry (DSC measurements revealed that an increase in the amount of BiFeO3 dopant resulted in a decrease in the orthorhombic-tetragonal and tetragonal-cubic phase transition temperature of the material. One percent BiFeO3 additive suppressed grain growth, which not only benefits the sintering of ceramics but also enhances the piezoelectric and ferroelectric properties, where d33=145pC/N, kp=0.31, Qm=80, Pr=11.3 μC cm−2 and Ec=16.5 kV cm−1. As xBF>0.01, both piezoelectric and ferroelectric properties decreased rapidly with an increasing amount of dopant.

  14. Anomalous spectral weight transfer at the superconducting transition of Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8+. delta

    Energy Technology Data Exchange (ETDEWEB)

    Dessau, D.S.; Wells, B.O.; Shen, Z.; Spicer, W.E. (Stanford Electronics Laboratories, Stanford University, Stanford, California 94305 (USA)); Arko, A.J.; List, R.S. (Los Alamos National Laboratories, Los Alamos, New Mexico 87545 (USA)); Mitzi, D.B.; Kapitulnik, A. (Department of Applied Physics, Stanford University, Stanford, California 94305 (USA))

    1991-04-22

    Anomalous spectral weight transfer at the superconducting transition of single-crystalline Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} was observed by high-resolution angle-resolved photoemission spectroscopy. As the sample goes superconducting, not only is there spectral weight transfer from the gap region to the pileup peak as in BCS theory, but along the {Gamma}-{ital {bar M}} direction there is also some spectral weight transfer from higher binding energies in the form of a dip. In addition, we note that at the superconducting transition there is a decrease (increase) in the occupied spectral weight for the spectra taken along {Gamma}-{ital {bar M}} ({Gamma}-{ital X}).

  15. Highly nonlinear property and threshold voltage of Sc2O3 doped ZnO-Bi2O3-based varistor ceramics

    Institute of Scientific and Technical Information of China (English)

    XU Dong; WU Jieting; JIAO Lei; XU Hongxing; ZHANG Peimei; YU Renhong; CHENG Xiaonong

    2013-01-01

    A series of ZnO-Bi2O3-based varistor ceramics doped with 0-0.4 mol.% Sc2O3 were prepared by high-energy ball milling and sintered at temperatures between 1000 and 1150 ℃.X-ray diffractometry (XRD) and scanning electron microscopy (SEM) were applied to characterize the phases and microstructure of the varistor ceramics.A DC parameter instrument for varistor ceramics was applied to investigate the electronic properties and Ⅴ-Ⅰ characteristics.The results showed that there were no changes in crystal structure with Sc2O3-doped varistor ceramics and that the average size of ZnO grain increased first and then decreased.The best electronic charactefistcs of the varistor ceramics prepared by high-energy ball milling were found in 0.3 mol.% Sc2O3-doped ZnO-Bi2O3-based ceramics sintered at 1000 ℃,which exhibited a threshold voltage of 821 V/mm,nonlinear coefficient of 62.1 and leakage current of 0.16 μA.

  16. Synthesis and Properties of [Bi0.5(Na1-xAgx)0.5]1-yBayTiO3 Piezoelectric Ceramics

    Science.gov (United States)

    Wu, Lang; Xiao, Ding-Quan; Lin, Dun-Min; Zhu, Jian-Guo; Yu, Ping

    2005-12-01

    A new group of ABO3-type lead-free piezoelectric ceramics, [Bi0.5(Na1-xAgx)0.5]1-yBayTiO3, was developed, and the corresponding invention patent was submitted. The ceramics were synthesized by the conventional ceramic sintering technique using electronic grade raw materials, and the preparation techniques are very stable and convenient. The crystalline phase, microstructure and electric properties of the ceramics were also investigated. All the ceramics have high densities of about 5.70-5.84 g/cm3, which are more than 95% of the theoretical values. This system provides high piezoelectric performances: d33=168 pC/N, kp=0.31 when x=0.06, y=0.06. Moreover, the samples doped with a moderate amount of Mn could increase the mechanical quality factor Qm and reduce the dielectric loss \\mathop{tg}δ simultaneously. The temperature dependence of piezoelectric properties measured show that at up to 180°C, d33 can still remain 126 pC/N for [Bi0.5(Na0.96Ag0.04)0.5]0.90Ba0.10TiO3 ceramics, which has a d33 of 137 pC/N at room temperature.

  17. Modification of physical and structural properties of Bi{sub 1.8}Pb{sub 0.4}Sr{sub 2}Ca{sub 2.2}Cu{sub 3}O{sub y} ceramics induced by annealing

    Energy Technology Data Exchange (ETDEWEB)

    Özkurt, Berdan, E-mail: berdanozkurt@mersin.edu.tr [Department of Energy Systems Engineering, Faculty of Tarsus Technology, University of Mersin, Mersin (Turkey); Madre, M.A.; Sotelo, A.; Diez, J.C. [ICMA (CSIC-Universidad de Zaragoza), María de Luna, 3, 50018 Zaragoza (Spain)

    2013-10-01

    The effect of annealing temperatures on the structural and superconducting properties of Bi-2223 ceramics prepared by the solid state reaction method has been investigated. Annealing temperatures were varied from 730 to 830 °C while time was kept constant at 50 h. Electrical resistivity studies showed that samples annealed at 830 °C for 50 h have the lowest resistivity values at room temperature while critical transition temperature increases slightly. XRD data have shown that all samples contain Bi-2223 as the major one. The highest diamagnetism behavior has been found in the sample treated at 830 °C. In addition, J{sub c} values of the samples, calculated from the hysteresis loops using the Bean's model, decreased with increasing annealing temperatures until 780 °C and increase for the highest annealing temperature which is 830 °C for this work.

  18. Josephson coupling between superconducting islands on single- and bi-layer graphene

    Science.gov (United States)

    Mancarella, Francesco; Fransson, Jonas; Balatsky, Alexander

    2016-05-01

    We study the Josephson coupling of superconducting (SC) islands through the surface of single-layer graphene (SLG) and bilayer graphene (BLG) in the long-junction regime, as a function of the distance between the grains, temperature, chemical potential and external (transverse) gate-voltage. For SLG, we provide a comparison with existing literature. The proximity effect is analyzed through a Matsubara Green’s function approach. This represents the first step in a discussion of the conditions for the onset of a granular superconductivity within the film, made possible by Josephson currents flowing between superconductors. To ensure phase coherence over the 2D sample, a random spatial distribution can be assumed for the SC islands on the SLG sheet (or intercalating the BLG sheets). The tunable gate-voltage-induced band gap of BLG affects the asymptotic decay of the Josephson coupling-distance characteristic for each pair of SC islands in the sample, which results in a qualitatively strong field dependence of the relation between Berezinskii-Kosterlitz-Thouless transition critical temperature and gate voltage.

  19. Influence of Pb-rich phases of precursor powder on microstructural evolution in the silver-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox superconducting tapes

    DEFF Research Database (Denmark)

    Chen, X.P.; Grivel, Jean-Claude; Li, M.Y.;

    2010-01-01

    The influence of Pb-rich phases of precursor powder on microstructural evolution during the first heat treatment of the silver-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox ((Bi,Pb)-2223/Ag) superconducting tapes was studied by means of in situ synchrotron X-ray diffraction. Three monofilament tapes were fabricat...

  20. Influence of Bi2O3 on microstructure and electrical properties of ZnO-SnO2 ceramics

    Directory of Open Access Journals (Sweden)

    Ivetić T.

    2007-01-01

    Full Text Available The effects of small amounts (0.5; 1.0 and 1.5 mol. % of bismuth oxide on the microstructure and electrical properties of ZnO-SnO2 ceramics have been studied. Starting powders of ZnO and SnO2 were mixed in the molar ratio 2:1. After adding Bi2O3 this mixture was mechanically activated for 10 minutes in a planetary ball mill, uniaxially pressed and sintered at 1300ºC for 2h. The phase composition of the sintered samples was analyzed by X-Ray Diffraction (XRD and by Energy Dispersive Spectrometer (EDS. Morphologies were examined by Scanning Electron Microscopy (SEM. An Impedance/Gain Phase Analyzer (HP 4194A was used to measure the impedance spectra (100Hz - 10MHz at different temperatures. The electrical DC resistivity/conductivity at different temperatures was measured using a High Resistance Meter (HP 4329A.

  1. Field induced microwave absorption in single crystal Bi (2212): Evidence for a superconductive glass state

    Energy Technology Data Exchange (ETDEWEB)

    Tyagi, S.; Gould, A.; Bhagat, S.M. (Centre for Research on Superconductivity, Dept. of Physics, Univ. of Maryland, College Park (USA)); Manheimer, M.A. (Lab. for Physical Sciences, College Park, MD (USA))

    1989-12-01

    The field induced microwave absorption P(H) at 35 GHz in Bi 2212 micaceous single crystals exhibits remarkable variations as temperature is increased from 1.3 K to Tc. For T< or approx.16 K, the hysteresis loops are highly reminiscent of those observed in spin glasses. At 30< or approx.T< or approx.50 K, they resemble those of a Type II superconductor. As suggested by the magnetization data, the micaceous nature causes a large enhancement in P(H) for 50

  2. Phase characteristics of 0.92Bi{sub 0.5}Na{sub 0.5}TiO{sub 3}-0.08BiAlO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Peng, Wei; Mao, Chaoliang; Liu, Zhen; Dong, Xianlin; Cao, Fei; Wang, Genshui, E-mail: genshuiwang@mail.sic.ac.cn [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China)

    2015-03-02

    The phase characteristics of 0.92Bi{sub 0.5}Na{sub 0.5}TiO{sub 3}-0.08BiAlO{sub 3} lead-free ceramics were investigated systematically. The loss tangent of poled sample shows a broad peak when heating to about 80 °C, i.e., depolarization temperature T{sub d}. The polarization-electric field hysteresis loops at different temperature exhibit the feature of ferroelectric (FE)- antiferroelectric (AFE) phase transition and the co-existence of FE and AFE phase. The pyroelectric coefficients curve confirms its diffusion behaviors. The initial hysteresis loop and switching current curves under T{sub d} indicate the co-existence of FE and AFE phase. The domain morphology of transmission electron microscopy supports the co-existence of FE and AFE phase. Our work not only exhibit that the FE and AFE phase characteristics of 0.92Bi{sub 0.5}Na{sub 0.5}TiO{sub 3}-0.08BiAlO{sub 3} ceramics but also they may be helpful for further investigation on lead-free ceramics.

  3. Superconducting and mechanical properties of the bulk Bi(pb)SCCO system prepared via solid state and ammonium nitrate precipitation methods

    Science.gov (United States)

    Safran, S.; Kılıçarslan, E.; Ozturk, H.; Alp, M.; Akdogan, M.; Asikuzun, E.; Ozturk, O.; Kılıç, A.

    2015-09-01

    We have investigated the effect of preparation method on superconducting and mechanical properties of Bi(Pb)-2223 bulk samples using Bi1.85Pb0.35Sr2Ca2Cu3O10±y stoichiometry. Solid-state reaction and ammonium nitrate precipitation methods have been used for fabrication of the bulk samples. In addition, the effect of annealing time on BSCCO samples have been studied. Structural, electrical, magnetic and microhardness analyses of samples are performed by the X-ray powder diffraction (XRD), the Scanning Electron Microscopy (SEM), DC resistivity, AC susceptibility and Vickers microhardness test. The critical transition temperature, phase purity, surface morphology and crystallinity of the prepared bulk samples are compared with each other. Elasticity (E), brittleness (Bi), fracture toughness (KIC) and yield strength (Y) values are also determined according to annealing time, applied load and production parameters of materials.

  4. Impedance analysis of Bi3.25La0.75Ti3O12 ferroelectric ceramic

    Indian Academy of Sciences (India)

    S Rachna; Surya M Gupta; S Bhattacharyya

    2008-09-01

    AC impedance spectroscopy technique has been used to study electrical properties of Bi3.25La0.75Ti3O12 (BLT) ceramic. Complex impedance plots were fitted with three depressed semicircles, which are attributed to crystalline layer, plate boundary and grain boundary and all three were found to comprise of universal capacitance nature [ = 0−1]. Grain boundary resistance and capacitance evaluated from complex impedance plots have larger values than that of plate boundary and crystalline layer. The activation energies (a) for DC-conductance in grain boundary, plate boundary and crystalline layer are 0.68 eV, 0.89 eV and 0.89 eV, respectively. Relaxation activation energies calculated from impedance plots showed similar values, 0.81 eV and 0.80 eV for crystalline layer and plate boundary, respectively. These activation energy values are found to be consistent with the a value of oxygen vacancies in perovskite materials. A mechanism is offered to explain the generation of oxygen vacancies in BLT ceramic and its role in temperature dependence of DC-conductance study.

  5. FABRICATION AND MECHANICAL PROPERTIES OF Na0.5Bi0.5TiO3–BaTiO3 LEAD-FREE PIEZOELECTRIC CERAMICS

    Directory of Open Access Journals (Sweden)

    PAN YUSONG

    2014-03-01

    Full Text Available Piezoelectric ceramics with 0.94Na0.5Bi0.5TO3–0.06BaTiO3 compositions were fabricated by solid state mixed oxide method and sintered at different temperatures varying from 1050°C to 1150°C to obtain dense ceramics. Phase analysis using X-ray diffraction showed tetragonal perovskite structure of Na0.5Bi0.5TO3 with no BaTiO3 peak detected. The SEM observation revealed that the crystal grain size of the piezoelectric ceramics is on the nano-size dimensions under all the sintering temperature. The study on the compressive mechanical characteristics showed that the compressive strength of the 0.94Na0.5Bi0.5TO3–0.06BaTiO3 piezoelectric ceramics increases with the rise of sintering temperature and sintering time. The change behavior of the compressive strength with the rise of cold pressure presents increasing firstly and then decreases.

  6. Effect of substitution of titanium by magnesium and niobium on structure and piezoelectric properties in (Bi1/2Na1/2)TiO3 ceramics

    Indian Academy of Sciences (India)

    Zhou Chang-Rong; Liu Xin-Yu; Li Wei-Zhou; Yuan Chang-Lai

    2011-12-01

    To develop new (Bi1/2Na1/2)TiO3-based ceramics with excellent piezoelectric properties, the similarities and the differences between PZT and (Bi1/2Na1/2)TiO3 ceramics were analysed. Based on the analysis, a new (Bi1/2Na1/2)TiO3-based piezoelectric ceramic of B-site substitution of complex ions (Mg1/3Nb2/3)4+ for Ti4+ was prepared by a conventional ceramic technique, and the effect of complex ions (Mg1/3Nb2/3)4+ addition on the microstructure, dielectric and piezoelectric properties was investigated. The research results show that all compositions are mono-perovskite phase and the grain size increases with increasing content of (Mg1/3Nb2/3)4+. The piezoelectric constant $d_{33}$ first increases and then decreases, and electromechanical coupling factor $k_{p}$ varies insignificantly with increasing content of (Mg1/3Nb2/3)4+.

  7. Effect of substitution of titanium by magnesium and niobium on structure and piezoelectric properties in (Bi1/2Na1/2)TiO3 ceramics

    Indian Academy of Sciences (India)

    Zhou Chang-Rong; Liu Xin-Yu; Li Wei-Zhou; Yuan Chang-Lai

    2009-02-01

    To develop new (Bi1/2Na1/2)TiO3-based ceramics with excellent piezoelectric properties, the similarities and the differences between PZT and (Bi1/2Na1/2)TiO3 ceramics were analysed. Based on the analysis, a new (Bi1/2Na1/2)TiO3-based piezoelectric ceramic of B-site substitution of complex ions (Mg1/3Nb2/3)4+ for Ti4+ was prepared by a conventional ceramic technique, and effect of complex ions (Mg1/3Nb2/3)4+ addition on the microstructure, dielectric and piezoelectric properties was investigated. The results show that all compositions are mono-perovskite phase and the grain size increases with increasing content of (Mg1/3Nb2/3)4+. The piezoelectric constant, 33, first increases and then decreases, and electromechanical coupling factor, p, varies insignificantly with increasing content of (Mg1/3Nb2/3)4+.

  8. Enhanced High Temperature Piezoelectrics Based on BiScO3-PbTiO3 Ceramics

    Science.gov (United States)

    Sehirlioglu, Alp; Sayir, Ali; Dynys, Fred

    2009-01-01

    High-temperature piezoelectrics are a key technology for aeronautics and aerospace applications such as fuel modulation to increase the engine efficiency and decrease emissions. The principal challenge for the insertion of piezoelectric materials is the limitation on upper use temperature which is due to low Curie-Temperature (TC) and increasing electrical conductivity. BiScO3-PbTiO3 (BS-PT) system is a promising candidate for improving the operating temperature for piezoelectric actuators due to its high TC (greater than 400 C). Bi2O3 was shown to be a good sintering aid for liquid phase sintering resulting in reduced grain size and increased resistivity. Zr doped and liquid phase sintered BS-PT ceramics exhibited saturated and square hysteresis loops with enhanced remenant polarization (37 microC per square centimeter) and coercive field (14 kV/cm). BS-PT doped with Mn showed enhanced field induced strain (0.27% at 50kV/cm). All the numbers indicated in parenthesis were collected at 100 C.

  9. Processing, Fabrication, Characterization and Device Demonstration of High Temperature Superconducting Ceramics

    Science.gov (United States)

    1994-07-30

    LCF determination derived from an extended Bean model , relies on the existence of a trapped magnetization, Mt, that is proportional to an (H-He) 2 . A...detection of the departure of a single point from the Meissner line. Likewise a "hysteritic method" for superconducting cylinders, also based on the Bean ... model , enables an H,, to be extracted from an extensive set of hysteritic-loss versus sweep-amplitude data taken above Hcj. TheO application of this

  10. Synthesis and Dielectric Properties of Ba3NaBiNb10O30 Ceramics

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A new niobate Ba3NaBiNb10O30 was synthesized by the solid state reaction.The reaction mixture was characterized by thermogravimetric and differential thermal analysis (TG-DTA),X-ray diffraction and dielectric constant measurements.The results show that Ba3NaBiNb10O30 has an orthorhombic tungsten bronze structure with space group Cmm2 and the unit cell parameters are a=1.7660(1) nm,a=1.7626(1) nm,c=0.78621(6) nm,Z=4.Ba3NaBiNb10O30 undergoes two phase transitions at 200℃ and 400℃,respectively.

  11. Sintering and grain size influence on the electrical properties of the Bi{sub 26}Mo{sub 9}WO{sub 69} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Fonseca, F.C.; Muccillo, R. [Comissao Nacional de Energia Nuclear, Sao Paulo, SP (Brazil). Inst. de Pesquisas Energeticas e Nucleares; Steil, M.C.; Vannier, R.N. [Lab. de Cristallochimie et Physicochimie du Solide, ENSCL, Villeneuve d' Ascq (France)

    2002-07-01

    In the field of oxide ion conduction, bismuth-based materials exhibit interesting electrical properties at moderate temperatures: 300 C - 600 C. The Bi{sub 26}Mo{sub 10-x}W{sub x}O{sub 69} solid solution is a one-dimensional ion conductor with a structure based on [Bi{sub 12}O{sub 14}]{sub {infinity}} columns. The sintering behaviour of the Bi{sub 26}Mo{sub 9}WO{sub 69} powder was studied by dilametric analysis. In order to investigate the influence of the microstructure on the electrical properties of the Bi{sub 26}Mo{sub 9}WO{sub 69} ceramics, dense samples with different grain sizes were produced by isostatic pressing and controlling sintering temperature and time. The electrical properties were studied by impedance spectroscopy. Impedance spectroscopy results show that the electrical conductivity depends on the microstructural properties, remarkably on the grain size. (orig.)

  12. Temperature Effects on Properties of Bi(2223) High Temperature Superconducting Tapes

    Institute of Scientific and Technical Information of China (English)

    WANG Zheng-Dao; CHEN Zhao-Jia; DUAN Zhen-Zhong; WANG Wen-Quan

    2001-01-01

    The critical current density Jc and the n-value have been studied from 40 K to critical temperature for four types of Bi-system 2223 tapes with different sheaths. The experimental results demonstrate that the change of Jc can be divided into three parts and the n-value has some decrease with a decrease in temperature. In engineering applications, a proper working temperature can be selected to satisfy the practical requirement. Furthermore,the temperature effects on critical stress for Ag-sheath tape was also studied. The results demonstrate that the critical stress does not change monotonically with a decrease in temperature. It increases first, then decreases with the further decrease in temperature.

  13. Relaxor behaviour in BaBi4Ti4O15 ceramics fabricated using the powders obtained by mechanochemically assisted synthesis route

    Indian Academy of Sciences (India)

    Sunil Kumar; K B R Varma

    2014-10-01

    Mechanochemically activated reactants were found to facilitate the synthesis of fine powders comprising 200–400 nm range crystallites of BaBi4Ti4O15 at a significantly lower temperature (700 °C) than that of solid-state reaction route. Reactants (CaCO3, Bi2O3 and TiO2) in stoichiometric ratio were ball milled for 48 h to obtain homogeneous mixture. The evolution of the BaBi4Ti4O15 phase was systematically followed using X-ray powder diffraction (XRD) technique. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to probe its structural and microstructural details. The electron diffraction studies established the presence of correlated octahedral rotations and associated long-range polar ordering. High-resolution TEM imaging nevertheless revealed structural inhomogeneities leading to intergrowth defects. Dense BaBi4Ti4O15 ceramics with an average grain size of 0.9 m were fabricated using mechanochemically assisted synthesized powders at relatively low temperature (1000 °C). The effect of grain size on the dielectric and relaxor behaviour of BaBi4Ti4O15 ceramics was investigated. Fine-grained ceramics (average grain size ∼ 0.9 m) showed higher diffusion in phase transition, lower temperature of phase transition, lower Vogel–Fulcher freezing temperature and higher activation energy for the polarization reversal than those for coarse-grained ceramics (average grain size ∼ 7 m) fabricated via the conventional solid-state reaction route.

  14. Enhanced ferroelectric polarization and magnetization in BiFe{sub 1−x}Sc{sub x}O{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Wang, C.A.; Pang, H.Z.; Zhang, A.H.; Lu, X.B.; Gao, X.S. [Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, South China Normal University, Guangzhou 510006 (China); Zeng, M., E-mail: zengmin@scnu.edu.cn [Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, South China Normal University, Guangzhou 510006 (China); Liu, J.-M., E-mail: liujm@nju.edu.cn [Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, South China Normal University, Guangzhou 510006 (China); National Laboratory of Solid State Microstructures and Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing 210093 (China)

    2015-10-15

    Highlights: • Single phase Sc doped BFO ceramics were successfully fabricated. • Dielectric constant and magnetization are enhanced in doped BFO system. • Polarization first increases and then decreases in doped BFO system. • M{sub r} of 0.0105 emu/g and P{sub r} of 16.1 μC/cm{sup 2} were revealed simultaneously at x = 0.01. - Abstract: Multiferroic BiFe{sub 1−x}Sc{sub x}O{sub 3} ceramics with x = 0.00–0.10 were synthesized by rapid liquid phase sintering. The influences of Sc doping on the crystalline structures, dielectric, ferroelectric, and magnetic behaviors of BiFeO{sub 3} ceramics were explored. The X-ray diffraction and the Raman spectrometric analysis revealed that all the samples are nearly single phase of rhombohedral structure with the incorporation of Sc ions into BiFeO{sub 3}. With increase doping concentration of x, the dielectric constant, dielectric loss, and remnant polarization for the doped BiFeO{sub 3} increase first and then drop down with further rise of x. A saturated ferroelectric polarization can be achieved at a small amount of Sc doping concentration (x < 0.03), with a optimized remnant polarization of 17.6 μC/cm{sup 2} at x = 0.03. Meanwhile, the magnetization is also slightly increased by introducing Sc dopant, with a maximum remnant magnetization of 0.0105 emu/g at x = 0.01. These results indicate that BiFeO{sub 3} ceramics with small amounts of Sc-doping may be promising for applications in magnetoelectric devices.

  15. Diffuse phase transition, piezoelectric and optical study of Bi0.5Na0.5TiO3 ceramic

    Indian Academy of Sciences (India)

    B Parija; T Badapanda; V Senthil; S K Rout; S Panigrahi

    2012-04-01

    Bismuth sodium titanate, Bi0.5Na0.5TiO3 (BNT) is considered to be an excellent candidate for a key material of lead-free dielectric ceramics. In this study, we propose the dielectric and optical study of single phase BNT powder prepared by solid-state reaction route. The phase formation and structural study were done by X-ray diffraction (XRD) which shows well developed crystallite with a pure perovskite phase. The ceramic was sintered at different temperatures from 1050°C to 1175°C to study the effect of sintering temperature on the morphology and density. It was found that the sample sintered at 1150°C shows the highest density. The microstructure of the ceramic was investigated by scanning electron microscopic (SEM) technique. The temperature-dependent dielectric study of the sample sintered at 1150°C was done in the frequency range of 50 kHz–1 MHz which shows a diffuse phase transition. The piezoelectric constant (33) was found to be 41 pCN-1. The P–E hysteresis loop confirms the ferroelectric behaviour in the ceramic. The UV–Vis spectrum indicated that the Bi0.5Na0.5TiO3 ceramic has an optical band gap of 2.94 eV.

  16. The Effect of Niobium Doping on the Electrical Properties of 0.4(Bi0.5K0.5TiO3-0.6BiFeO3 Lead-Free Piezoelectric Ceramics

    Directory of Open Access Journals (Sweden)

    John G. Fisher

    2015-12-01

    Full Text Available Ceramics in the system (Bi0.5K0.5TiO3-BiFeO3 have good electromechanical properties and temperature stability. However, the high conductivity inherent in BiFeO3-based ceramics complicates measurement of the ferroelectric properties. In the present work, doping with niobium (Nb is carried out to reduce the conductivity of (Bi0.5K0.5TiO3-BiFeO3. Powders of composition 0.4(K0.5Bi0.5Ti1−xNbxO3-0.6BiFe1−xNbxO3 (x = 0, 0.01 and 0.03 are prepared by the mixed oxide method and sintered at 1050 °C for 1 h. The effect of Nb doping on the structure is examined by X-ray diffraction. The microstructure is examined by scanning electron microscopy. The variation in relative permittivity with temperature is measured using an impedance analyzer. Ferroelectric properties are measured at room temperature using a Sawyer Tower circuit. Piezoelectric properties are measured using a d33 meter and a contact type displacement sensor. All the samples have high density, a rhombohedral unit cell and equiaxed, micron-sized grains. All the samples show relaxor-like behavior. Nb doping causes a reduction in conductivity by one to two orders of magnitude at 200 °C. The samples have narrow P-E loops reminiscent of a linear dielectric. The samples all possess bipolar butterfly S-E loops characteristic of a classic ferroelectric material. Nb doping causes a decrease in d33 and Smax/Emax.

  17. Superconductive articles including cerium oxide layer

    Science.gov (United States)

    Wu, Xin D.; Muenchausen, Ross E.

    1993-01-01

    A ceramic superconductor comprising a metal oxide substrate, a ceramic high temperature superconductive material, and a intermediate layer of a material having a cubic crystal structure, said layer situated between the substrate and the superconductive material is provided, and a structure for supporting a ceramic superconducting material is provided, said structure comprising a metal oxide substrate, and a layer situated over the surface of the substrate to substantially inhibit interdiffusion between the substrate and a ceramic superconducting material deposited upon said structure.

  18. Testing the Itinerancy of Spin Dynamics in Superconducting Bi2Sr2CaCu2O8C+δ

    Energy Technology Data Exchange (ETDEWEB)

    Xu, G.; Gu, G.D.; Hücker, M.; Fauqué, B.; Perring, T.G.; Regnault, L.P.; Tranquada, J.M.

    2009-09-01

    Much of what we know about the electronic states of high-temperature superconductors is due to photoemission and scanning tunnelling spectroscopy studies of the compound Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}}. The demonstration of well-defined quasiparticles in the superconducting state has encouraged many theorists to apply the conventional theory of metals, Fermi-liquid theory, to the cuprates. In particular, the spin excitations observed by neutron scattering at energies below twice the superconducting gap energy are commonly believed to correspond to an excitonic state involving itinerant electrons. Here, we present the first measurements of the magnetic spectral weight of optimally doped Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} in absolute units. The lack of temperature dependence of the local spin susceptibility across the superconducting transition temperature, T{sub c}, is incompatible with the itinerant calculations. Alternatively, the magnetic excitations could be due to local moments, as the magnetic spectrum is similar to that in La{sub 1.875}Ba{sub 0.125}CuO{sub 4}, where quasiparticles and local moments coexist.

  19. Superconductivity up to 110 K in Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/0/sub 10/ compounds

    Energy Technology Data Exchange (ETDEWEB)

    Lejay, P.; Rango, P. de; Sulpice, A.; Giordanengo, B.; Tournier, R.; Retoux, R.; Deslandes, S.; Michel, C.; Hervieu, M.; Raveau, B.

    1989-05-01

    In the Bi-Sr-Ca-Cu-0 system, we have studied the compound with the ideal formula Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/0/sub 10/, responsible for the superconductivity up to 110 K. The magnetic measurements reveal the presence of two phases in the samples with superconducting transitions up to 80 K and 110 K. By varying the composition and the thermal treatment of those samples, we have succeeded in increasing the amount of the superconducting phase with T/sub c/ up to 110 K. The Meissner effect reaches 30 % of - 3/8 ..pi.. at 90 K for the undoped samples and more than 50 % for the samples doped with Pb. Because of the high reversibility of the magnetization versus magnetic field around T/sub c/, we have evaluated the critical thermodynamic field. This one gives an electronic specific heat coefficient similar to the one of YBaCu0 compounds.

  20. Residual tensile stresses and piezoelectric properties in BiFeO3-Bi(Zn1/2Ti1/2O3-PbTiO3 ternary solid solution perovskite ceramics

    Directory of Open Access Journals (Sweden)

    Weilin Zheng

    2016-08-01

    Full Text Available For low dielectric loss perovskite-structured (1-x-yBiFeO3-xBi(Zn1/2Ti1/2O3-yPbTiO3 (BF-BZT-PT (x = 0.04-0.15 and y = 0.15-0.26 ceramics in rhombohedral/tetragonal coexistent phase, structural phase transitions were studied using differential thermal analyzer combined with temperature-dependent dielectric measurement. Two lattice structural phase transitions are disclosed in various BF-BZT-PT perovskites, which is different from its membership of BiFeO3 exhibiting just one lattice structural phase transition at Curie temperature TC= 830oC. Consequently, residual internal tensile stresses were revealed experimentally through XRD measurements on ceramic pellets and counterpart powders, which are reasonably attributed to special structural phase transition sequence of BF-BZT-PT solid solution perovskites. Low piezoresponse was observed and argued extrinsically resulting from residual tensile stresses pinning ferroelectric polarization switching. Post-annealing and subsequent quenching was found effective for eliminating residual internal stresses in those BZT-less ceramics, and good piezoelectric property of d33 ≥ 28 pC/N obtained for 0.70BF-0.08BZT-0.22PT and 0.05 wt% MnO2-doped 0.70BF-0.04BZT-0.26PT ceramics with TC ≥ 640oC, while it seemed no effective for those BZT-rich BF-BZT-PT ceramics with x = 0.14 and 0.15 studied here.

  1. sup 119 Sn-Moessbauer study on the normal lattice vibration of superconducting Bi(Pb) sub 2 Sr sub 2 Ca sub 2 Cu sub 3 Sn sub 0. 015 O sub 10-y

    Energy Technology Data Exchange (ETDEWEB)

    Nishida, Tetsuaki; Takashima, Yoshimasa (Kyushu Univ., Fukuoka (Japan). Faculty of Science); Katada, Motomi; Miura, Norio; Deshimaru, Yuichi; Otani, Tetsuya; Yamazoe, Noboru; Matsumoto, Yasukuni

    1991-04-01

    The {sup 119}Sn-Moessbauer spectrum of superconducting Bi(Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}Sn{sub 0.015}O{sub 10-y} ceramic, having the T{sub c} of 108 K, consists of an intense doublet peak with the {delta} of 0.18 mmcenter dots{sup -1} and the {Delta} of 1.01 mmcenter dot s{sup -1} at room temperature. The {delta} and {Delta} indicate that the Sn{sup 4+} is substituted for the copper ion in the triangular CuO{sub 3} site of the CuO{sub 4} layer. The {delta} and the absorption area increase gradually with decreasing temperature and become saturated at about 30 K, being consistent with the theoretical curves obtained from the 'combined Debye and Einstein model'. Only the normal vibration without the softening is observed in the CuO{sub 4} layer. (author).

  2. Fabrication and characterization of nanostructured Ba-doped BiFeO3 porous ceramics

    Directory of Open Access Journals (Sweden)

    Mostafavi E.

    2016-03-01

    Full Text Available Nanostructured barium doped bismuth ferrite, Bi₀.₈Ba₀.₂FeO₃ porous ceramics with a relatively high magnetic coercivity was fabricated via sacrificial pore former method. X-ray diffraction results showed that 20 wt.% Ba doping induces a structural phase transition from rhombohedral to distorted pseudo-cubic structure in the final porous samples. Moreover, utilizing Bi₀.₈Ba₀.₂FeO₃ as the starting powder reduces the destructive interactions between the matrix phase and pore former, leading to an increase in stability of bismuth ferrite phase in the final porous ceramics. Urea-derived Bi₀.₈Ba₀.₂FeO₃ porous ceramic exhibits density of 4.74 g/cm³ and porosity of 45 % owing the uniform distribution of interconnected pores with a mean pore size of 7.5 μm. Well defined nanostructured cell walls with a mean grain size of 90 nm were observed in the above sample, which is in a good accordance with the grain size obtained from BET measurements. Saturation magnetization decreased from 2.31 in the Bi₀.₈Ba₀.₂FeO₃ compact sample to 1.85 A m²/kg in urea-derived Bi₀.₈Ba₀.₂FeO₃ porous sample; moreover, coercivity increased from 284 to 380 kA/m.

  3. Experimental evidence for s-wave pairing symmetry in superconducting Cu(x)Bi2Se3 single crystals using a scanning tunneling microscope.

    Science.gov (United States)

    Levy, Niv; Zhang, Tong; Ha, Jeonghoon; Sharifi, Fred; Talin, A Alec; Kuk, Young; Stroscio, Joseph A

    2013-03-15

    Topological superconductors represent a newly predicted phase of matter that is topologically distinct from conventional superconducting condensates of Cooper pairs. As a manifestation of their topological character, topological superconductors support solid-state realizations of Majorana fermions at their boundaries. The recently discovered superconductor Cu(x)Bi(2)Se(3) has been theoretically proposed as an odd-parity superconductor in the time-reversal-invariant topological superconductor class, and point-contact spectroscopy measurements have reported the observation of zero-bias conductance peaks corresponding to Majorana states in this material. Here we report scanning tunneling microscopy measurements of the superconducting energy gap in Cu(x)Bi(2)Se(3) as a function of spatial position and applied magnetic field. The tunneling spectrum shows that the density of states at the Fermi level is fully gapped without any in-gap states. The spectrum is well described by the Bardeen-Cooper-Schrieffer theory with a momentum independent order parameter, which suggests that Cu(x)Bi(2)Se(3) is a classical s-wave superconductor contrary to previous expectations and measurements.

  4. Magnetic measurements at pressures above 10 GPa in a miniature ceramic anvil cell for a superconducting quantum interference device magnetometer.

    Science.gov (United States)

    Tateiwa, Naoyuki; Haga, Yoshinori; Matsuda, Tatsuma D; Fisk, Zachary

    2012-05-01

    A miniature ceramic anvil high pressure cell (mCAC) was earlier designed by us for magnetic measurements at pressures up to 7.6 GPa in a commercial superconducting quantum interference magnetometer [N. Tateiwa et al., Rev. Sci. Instrum. 82, 053906 (2011)]. Here, we describe methods to generate pressures above 10 GPa in the mCAC. The efficiency of the pressure generation is sharply improved when the Cu-Be gasket is sufficiently preindented. The maximum pressure for the 0.6 mm culet anvils is 12.6 GPa when the Cu-Be gasket is preindented from the initial thickness of 300-60 μm. The 0.5 mm culet anvils were also tested with a rhenium gasket. The maximum pressure attainable in the mCAC is about 13 GPa. The present cell was used to study YbCu(2)Si(2) which shows a pressure induced transition from the non-magnetic to magnetic phases at 8 GPa. We confirm a ferromagnetic transition from the dc magnetization measurement at high pressure. The mCAC can detect the ferromagnetic ordered state whose spontaneous magnetic moment is smaller than 1 μ(B) per unit cell. The high sensitivity for magnetic measurements in the mCAC may result from the simplicity of cell structure. The present study shows the availability of the mCAC for precise magnetic measurements at pressures above 10 GPa.

  5. Effect of increasing lanthanum substitution and the sintering procedures on the properties of SrBi4Ti4O15 ceramics

    Indian Academy of Sciences (India)

    A Rambabu; K C James Raju

    2015-09-01

    Lanthanum-substituted SrBi4Ti4O15 (SBTi) ceramic, that is SrBi4–LaTi4O15 (SBLTi), samples were calcined by solid-state reaction and densified using the microwave sintering and conventional sintering techniques. Their structural, morphological and mechanical properties were investigated. The microwave sintered samples showed high densities like 95% of the theoretical density with short duration exposures. Compared with SBTi ceramics and other lanthanide-substituted compositions, the incorporation of La3+ results in clear improvement in properties for SBLT ( ∼ 0.75) with respect to the values of hardness and Young’s modulus of the microwave sintered samples (8.8–12.5 and 160–180 GPa) are higher than that for conventional sintered (8–10 and 135–155 GPa) samples.

  6. Investigations of electrical properties of Nd substituted BiFeO3 multiferroic ceramics

    Science.gov (United States)

    Rao, T. Durga; Asthana, Saket

    2013-06-01

    Polycrystalline BiFeO3 (BFO) and Bi0.9Nd0.1FeO3 (BNFO) compounds were synthesized by conventional solid-state route. All the compounds were crystallized in rhombohedral structure with R3c (IUCr No. 161) space group. Negative temperature coefficient of Resistance character has been observed from Complex impedance studies. ac conductivity in these compounds follows universal power law. Correlated Barrier Hopping (CBH) model has been employed to explain the charge carries transport mechanism. Density of states near Fermi level observed to be decreasing with the Nd substitution. Improved insulating character and decrease in density of states in BNFO compound suggested that possible reduction in oxygen vacancies. Activation energies calculated from Arrhenius plots revealed that electronic hopping, oxygen vacancies movements are the contributors to the ac conduction in the measured temperature range.

  7. Maxwell-Wagner relaxation and magnetodielectric properties of Bi0.5La0.5MnO3 ceramics

    Science.gov (United States)

    Turik, A. V.; Pavlenko, A. V.; Reznichenko, L. A.

    2016-08-01

    The complex permittivity ɛ = ɛ'- iɛ″ of manganite bismuth-lanthanum Bi0.5La0.5MnO3 ceramics has been measured at temperature T = 78 K in the frequency range f = 200-105 Hz and in the magnetic induction range B = 0-5 T. Dielectric relaxation and the pronounced magnetodielectric effect have been detected. The explanation based on the superposition of Maxwell-Wagner relaxation and the magnetoresistance effect has been proposed.

  8. Ergodic Relaxor State with High Energy Storage Performance Induced by Doping Sr0.85Bi0.1TiO3 in Bi0.5Na0.5TiO3 Ceramics

    Science.gov (United States)

    Li, Qing-Ning; Zhou, Chong-Rong; Xu, Ji-Wen; Yang, Ling; Zhang, Xin; Zeng, Wei-Dong; Yuan, Chang-Lai; Chen, Guo-Hua; Rao, Guang-Hui

    2016-10-01

    The large maximum polarization P max and low remnant polarization P r in relaxor ferroelectrics are key features for the energy storage density ( W) and energy-storage efficiency ( η) in materials selection. In this study, the ergodic relaxor (ER) state with high energy storage performance associated with low P r and large P max, induced by Sr0.85Bi0.1TiO3(SBT) addition in (1 - x)Bi0.5Na0.5TiO3- xSr0.85Bi0.1TiO3 (BNT-SBT x with x = 0.25-0.45, Bi0.5Na0.5TiO3 abbreviated as BNT) ceramics has been observed. In particular, significantly increased energy storage density ( W = 1.5 J/cm3) and energy-storage efficiency ( η = 73%) are obtained for BNT-SBT ergodic relaxor ceramics. These results suggest a new means of designing lead-free energy-storage materials.

  9. The Effect of Gd/Nd Doping on Phase Structure and Ferroelectric Properties of BiFeO3 Ceramics%Gd/Nd掺杂对BiFeO3结构和铁电性能的影响

    Institute of Scientific and Technical Information of China (English)

    李海宁; 陈镇平; 王春梅; 李涛; 代海洋

    2011-01-01

    采用快速液相烧结工艺制备了多铁陶瓷材料Bi1-xGdxFeO3(x=0.00,0.05,0.10,0.15)和Bi1-xNdxFeO3(x=0.00,0.05,0.10),研究了稀土离子Gd/Nd掺杂对多铁材料BiFeO3相结构和铁电性能的影响.X射线衍射谱显示对于Gd/Nd掺杂Bi1-xRxFeO3体系,适量掺杂有助于消除体系中的杂相;随着掺杂量的增加,体系的相结构有从菱方钙钛矿向三斜转变的趋势.电滞回线测试结果表明稀土掺杂改善了BiFeO3的铁电性能,掺杂后样品的剩余极化强度均有不同程度的提高.通过比较Gd/Nd掺杂体系的剩余极化强度,分析了样品铁电性的改善与掺杂稀土离子半径之间的关联.%Multiferroic ceramic samples of Bi1-xGdxFeO3(x=0. 00,0. 05,0. 10,0. 15) and Bi1-xNdxFeO3 (x = 0. 00,0. 05,0. 10) have been prepared by the rapid liquid phase sintering technique. The effects of Gd/Nd substitution on phase structure and ferroelectric properties of multiferroic BiFeO3 ceramics are investigated. XRD results show that the appropriate doping content of Gd/Nd could be helpful to reduce impurity phases for Bi1-xRxFeO3 samples. The phase structure has a tendency from rhombohedral structure to triclinic structure with increasing x. Experimental results of hysteresis loop suggest that the ferroelectric properties of BiFeO3 are improved and the remanent polarization is increased by doping. By comparing the the rem-anent polarization of Gd and Nd doping samples, the relationship between the ferroelectric properties and the radius of rare-earth ions is analyzed.

  10. Dielectric and Magnetic Properties of Ba(Fe1/2Ta1/2)O3-BiFeO3 Ceramics

    Science.gov (United States)

    Manotham, S.; Butnoi, P.; Jaita, P.; Pinitsoontorn, S.; Sweatman, D.; Eitssayeam, S.; Pengpat, K.; Rujijanagul, G.

    2016-11-01

    The properties of (1- x)Ba(Fe1/2Ta1/2)O3- xBiFeO3 [(1- x)BFT- xBFO] ( x = 0.0, 0.1, 0.3, 0.5) ceramics have been investigated. (1- x)BFT- xBFO powders were synthesized by a modified two-step calcination technique, and ceramics were fabricated by a conventional technique. X-ray diffraction (XRD) analysis revealed that the modified ceramics exhibited a mixture of BFT cubic phase and BFO rhombohedral phase. The peaks shift increased with increasing BFO content to a maximum value for the composition with x = 0.5. The overall shift of the XRD patterns indicated distortion of the unit cell, which may be due to ions from BFO entering the BFT lattice. BFO additive promoted grain growth, while the maximum density of the studied ceramics was observed for the x = 0.1 composition. The modified ceramics presented enhanced thermal and frequency stability of the dielectric constant. BFO additive also reduced the loss tangent for the system. Improvement of the magnetic behavior was observed after adding BFO. Furthermore, all the ceramics, including pure BFT (a nonmagnetic phase at room temperature), presented a magnetocapacitance effect, which can be related to magnetoresistance along with Maxwell-Wagner polarization effects.

  11. LiBiO2掺杂的低温烧结PSZT压电陶瓷%Low-temperature Sintering of PSZT Ceramics Doped with LiBiO2

    Institute of Scientific and Technical Information of China (English)

    刘越彦; 尚勋忠; 孙锐; 郭金明; 周桃生; 常钢; 何云斌

    2012-01-01

    By a two-step solid state synthesis method, low-temperature sintering of Pb0.95 Sr0.05 (Zr0.54 Ti0.46 ) O3 piezoelectric ceramics were achieved with LiBiO2 addition. It was found that the LiBiO2 addition could not only promote the sinterability by forming a liquid phase during the sintering process, but also improve the performances of the resultant ceramics. The experimental results showed that, with addition of proper amount LiBiO2 as sintering aid, the sintering temperature of PSZT ceramics could be brought down to 10S0 ℃, 240-340 ℃ lower than that of PSZT ceramics without LiBiO2 addition. When doped with 1.0wt% LiBiO2 and sintered at 1050 ℃ for 4 h, the PSZT ceramics achieved optimum properties: d33 =425 pC/N,kp =57.62% ,Td =350 ℃,εT33/εo =1543, tanδ =0.0216,p =7.45 g/cm3. The LiBiO2 doped PSZT ceramics show potential use in the laminated piezoelectric devices.%采用固相二步合成法,通过在预烧粉料中添加LiBiO2,制备出一种低温烧结的Pb0.95Sr0.05(Zr0.54Ti0.46)O3压电陶瓷材料.LiBiO2的添加具有降低烧结温度同时提高陶瓷性能的优点.实验结果表明:适量的LiBiO2掺杂,可形成过渡液相烧结,使烧结温度降低到950~1050℃,比未添加时的烧结温度低240~340℃.当w(LiBiO2) =1.0%,陶瓷达到最佳压电性能:压电应变常数d33=425 pC/N,平面机电耦合系数kp=57.62%,退极化温度Td=350℃,相对介电常数ε33T/ε0=1543,介电损耗tanδ=0.0216,剩余极化强度Pr=35.51 μC/cm2,体积密度p =7.45g/cm3.该材料可应用于低温共烧的叠层压电器件中.

  12. Relaxor behaviour and dielectric properties of BiFeO3 doped Ba(Zr0.1Ti0.9)O3 ceramics

    Indian Academy of Sciences (India)

    I Kallel; Z Abdelkafi; N Abdelmoula; A Simon; H Khemakhem

    2013-10-01

    Ba1−Bi(Ti0.9Zr0.1)1−FeO3 ( = 0–0.075) ceramics are prepared using a conventional solid state reaction method. X-ray diffraction shows the presence of a single phase. Addition of Bi3+ and Fe3+ strongly influences the crystal structure and dielectric properties of the ceramics. The evolution from a normal ferroelectric to a relaxor ferroelectric is emphasized. Ba0.99Bi0.01(Ti0.9Zr0.1)0.99Fe0.01O3 ceramic shows a relaxor behaviour at room temperature with m =12 K. – hysteresis loop of the composition, = 0.007, shows a remanent polarization (r) of 0.5 C/cm2 with a coercive field (C) of 2 kV/cm. Raman spectra of all compounds are performed and correlated well with the X-ray diffraction and dielectric measurement results.

  13. Room temperature structure and multiferroic properties in Bi{sub 0.7}La{sub 0.3}FeO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Carvalho, T.T., E-mail: tcarvalho@utad.pt [CQVR and Chemistry Department, University of Trás-os-Montes and Alto Douro, Apartado 1013, 5001-801 Vila Real (Portugal); Fernandes, J.R.A. [INESC TEC, Optoelectronic and Electronic System Unit, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Physics Department, University of Trás-os-Montes and Alto Douro, Apartado 1013, 5001-801 Vila Real (Portugal); Perez de la Cruz, J. [INESC TEC, Optoelectronic and Electronic System Unit, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Vidal, J.V.; Sobolev, N.A. [Physics Department and I3N, University of Aveiro, 3810-193 Aveiro (Portugal); Figueiras, F.; Das, S.; Amaral, V.S. [Physics Department and CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Almeida, A.; Agostinho Moreira, J. [IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Faculty of Sciences, University of Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Tavares, P.B. [CQVR and Chemistry Department, University of Trás-os-Montes and Alto Douro, Apartado 1013, 5001-801 Vila Real (Portugal)

    2013-03-25

    Highlights: ► We obtain reproducible results in ceramics synthesized by different methods. ► We report an incommensurate modulated structure for Bi{sub 0.7}La{sub 0.3}FeO{sub 3} ceramics. ► We report the piezoelectric coefficient for this composition. ► The obtain structure is related with Raman spectra and ferroelectric properties. -- Abstract: Single phase Bi{sub 0.7}La{sub 0.3}FeO{sub 3} ceramic samples were successfully synthesized by sol–gel combustion and co-precipitation methods, performing a final sintering at 820–870 °C from 10 up to 180 min. Rietveld refinements of the XRD data detected small satellite peaks that were successfully indexed by an incommensurated modulated structure model. Lanthanum doping improves magnetic response, reduces the leakage current and dielectric losses. The piezoelectric coefficient was reported for the first time in the Bi{sub 0.7}La{sub 0.3}FeO{sub 3} composition.

  14. Low Temperature Broad Band Dielectric Spectroscopy of Multiferroic Bi6Fe2Ti3O18 Ceramics

    Directory of Open Access Journals (Sweden)

    Lisińska-Czekaj A.

    2016-09-01

    Full Text Available In the present research the tool of broadband dielectric spectroscopy was utilized to characterize dielectric behavior of Bi6Fe2Ti3O18 (BFTO Aurivillius-type multiferroic ceramics. Dielectric response of BFTO ceramics was studied in the frequency domain (Δν=0.1Hz – 10MHz within the temperature range ΔT=-100°C – 200°C. The Kramers-Kronig data validation test was employed to validate the impedance data measurements and it was found that the measured impedance data exhibited good quality justifying further analysis. The residuals were found to be less than 1%, whereas the “chi-square” parameter was within the range χ2~10−7−10−5. Experimental data were analyzed using the circle fit of simple impedance arc plotted in the complex Z”-Z’ plane (Nyquist plot. The total ac conductivity of the grain boundaries was thus revealed and the activation energy of ac conductivity for the grain boundaries was calculated. It was found that activation energy of ac conductivity of grain boundaries changes from EA=0.20eV to EA=0.55eV while temperature rises from T=-100°C up to T=200°C. On the base of maxima of the impedance semicircles (ωmτm=1 the relaxation phenomena were characterized in terms of the temperature dependence of relaxation times and relevant activation energy was calculated (EA=0.55eV.

  15. Atomic-scale microstructures, Raman spectra and dielectric properties of cubic pyrochlore-typed Bi1.5MgNb1.5O7 dielectric ceramics

    KAUST Repository

    Li, Yangyang

    2014-07-01

    Single-phase cubic pyrochlore-typed Bi1.5MgNb 1.5O7 (BMN) dielectric ceramics were synthesized at temperatures of 1050-1200 °C by solid-state reaction method. Their atomic-scale microstructures and dielectric properties were investigated. X-ray diffraction patterns revealed that the BMN ceramics had an average cubic pyrochlore structure, whereas the Raman spectra indicated that they had an essentially cubic symmetry with small local deviations at the A and O\\' sites of the cubic pyrochlore structure. This was confirmed by selected electron area diffraction (SAED) patterns, where the reflections of {442} (not allowed in the cubic pyrochlore with Fd3̄m symmetry) were clearly observed. SEM and TEM images revealed that the average grain size was increased with the sintering temperature, and an un-homogeneous grain growth was observed at high temperatures. HRTEM images and SAED patterns revealed the single-crystalline nature of the BMN ceramic grains. Energy dispersive spectroscopy (EDS) elemental mapping studies indicated that the compositional distributions of Bi, Mg, Nb and O elements in the ceramic grains were homogenous, and no elemental precipitation was observed at the grain boundary. Quantitative EDS data on ceramic grains revealed the expected cationic stoichiometry based on the initial composition of Bi1.5MgNb1.5O7. Dielectric constants of all the BMN samples exhibited almost frequency independent characteristic in the frequency range of 102-106 Hz, and the highest value was 195 for the BMN ceramics sintered at sintered at 1150 °C with the highest bulk density. The dielectric losses were stable and less than 0.002 in the frequency range of 102-105 Hz. The high dielectric constants of the present BMN samples can be ascribed to the local atomic deviations at the A and O\\' sites from the ideal atomic positions of the pyrochlore structure, which affect the different polarization mechanisms in the BMN ceramics, and which in turn enhance the dielectric

  16. Diffuse phase transition and high-temperature dielectric relaxation study on (Bi0.5Na0.5)1-xBaxTiO3 ceramics

    Science.gov (United States)

    Chen, Feng; Liu, Qiu-Xiang; Tang, Xin-Gui; Jiang, Yan-Ping; Yue, Jing-Long; Li, Jin-Kai

    2016-09-01

    Lead free (Bi0.5Na0.5)1-xBaxTiO3 (x=0.6, 0.7, 0.8, 0.9) ferroelectric ceramics were synthesized by the traditional solid state reaction method. Sintering was carried out at 1200 °C for 2 h in air atmosphere. The structural, microstructure and Ferroelectric of ceramics were investigated. In dielectric studies, a diffuse phase transition was exhibited and a dielectric relaxation behavious was observed at high temperature range. Impedance analysis characterized grain and grain boundaries resistivities of the ceramics and calculated activation energy and the activation energy for conduction. Polaron theory indicates that the relaxation of the samples at high temperatures was associated with the hopping ions caused by oxygen vacancies.

  17. Multiferroic properties of nanocrystalline BiFe{sub 1−x}Ni{sub x}O{sub 3} (x=0.0–0.15) perovskite ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Chaudhari, Yogesh [Department of Physics, School of Physical Sciences, North Maharashtra University, Jalgaon 425001, Maharastra (India); Department of Physics, Shri. Pancham Khemaraj Mahavidyalaya, Sawantwadi 416510, Maharastra (India); Mahajan, Chandrashekhar M. [Department of Engineering Sciences and Humanities (DESH), Vishwakarma Institute of Technology, Pune 411 016, Maharastra (India); Singh, Amrita [Magnetics and Advanced Ceramics Laboratory, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016 (India); Jagtap, Prashant [Department of Physics, School of Physical Sciences, North Maharashtra University, Jalgaon 425001, Maharastra (India); Chatterjee, Ratnamala [Magnetics and Advanced Ceramics Laboratory, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016 (India); Bendre, Subhash, E-mail: bendrest@gmail.com [Department of Physics, School of Physical Sciences, North Maharashtra University, Jalgaon 425001, Maharastra (India)

    2015-12-01

    Ni doped BiFeO{sub 3} (x=0, 0.05, 0.1 and 0.15) nanocrystalline ceramics were synthesized by the solution combustion method (SCM) to obtain optimal multiferroic properties. The effect of Ni doping on structural, morphological, ferroelectric, magnetic and dielectric properties of BiFeO{sub 3} was studied. The structural investigations by using X-ray diffraction (XRD) pattern confirmed that BiFe{sub 1−x}Ni{sub x}O{sub 3} ceramics have rhombhohedral perovskite structure. The ferroelectric hysteresis measurements for BiFe{sub 1−x}Ni{sub x}O{sub 3} (x=0, 0.05, 0.1, 0.15) compound at room temperature found to exhibit unsaturated behavior and presents partial reversal of polarization. The magnetic measurements demonstrated an enhancement of ferromagnetic property due to Ni doping in BiFeO{sub 3} when compared with undoped BiFeO{sub 3}. The variation of dielectric constant with temperature in BiFe{sub 0.9}Ni{sub 0.1}O{sub 3} and BiFe{sub 0.85}Ni{sub 0.15}O{sub 3} samples evidenced an apparent dielectric anomaly around 350 °C and 300 °C which corresponds to antiferromagnetic to paramagnetic phase transition of (T{sub N}) of BiFeO{sub 3}. The dependence of room temperature dielectric properties on frequency signifies that both dielectric constant (ε) and dielectric loss (tan δ) are the strong function of frequency. The results show that solution combustion method leads to synthesis of an excellent and reproducible BiFe{sub 1−x}Ni{sub x}O{sub 3} multiferroic ceramics. - Highlights: • Synthesis of BiFe{sub 1−x}Ni{sub x}O{sub 3} (x=0, 0.05, 0.1 and 0.15) multiferroic ceramics. • Solution Combustion Method (SCM). • Ferroelectric and dielectric properties of undoped and Ni doped BiFeO{sub 3} ceramics. • High temperature synthesis of BiFe{sub 1−x}Ni{sub x}O{sub 3} multiferroic ceramics. • First detailed report about SCM synthesized the BiFe{sub 1−x}Ni{sub x}O{sub 3} ceramics.

  18. Phase Transition and Microwave Dielectric Properties of Low-Temperature Sintered BiCu2VO6 Ceramic and its Chemical Compatibility with Silver

    Science.gov (United States)

    Li, Chunchun; Xiang, Huaicheng; Fang, Liang

    2016-01-01

    In this work, a low-firing microwave dielectric ceramic BiCu2VO6 with monoclinic structure was prepared through a solid state reaction method. Dense ceramic could be obtained when sintered at 740°C with a relative density about 96.7%. A diffusive phase transition was observed from the temperature dependence of the relative permittivity and loss tangent. The best sintered sample at 740°C exhibited the optimum microwave dielectric properties with a relative permittivity ~22.7, a quality factor ~11,960 GHz (at 11.0 GHz), and a temperature coefficient of resonant frequency of -17.2 ppm/°C. From the x-ray diffraction, backscattered electron imaging results of the cofired sample with 20 wt.% silver, the BiCu2VO6 ceramic was found not to react with Ag at 740°C. It might be promising for the low-temperature cofired ceramics and dielectric resonator applications.

  19. Influence of BiFeO3 Additions on the Electrical and Magnetic Properties of La0.7Ca0.3MnO3 Ceramics

    Science.gov (United States)

    Luo, B. C.; Dong, H. J.

    2016-07-01

    (1 - x) La0.7Ca0.3MnO3- xBiFeO3 (0 ≤ x ≤ 0.1) ceramics were prepared by a solid state reaction method, and the structural, magnetic, electrical and thermoelectric power properties have been investigated. The single-phase (1 - x) La0.7Ca0.3MnO3- xBiFeO3 solid solutions with orthorhombic structure are achieved for x ≤ 0.1, and the lattice parameters of La0.7Ca0.3MnO3 ceramics keep equivalence with BiFeO3 additions. In contrast, both the ferromagnetic-paramagnetic transition temperature and the metal-insulator transition temperature monotonically shift towards lower temperature, and the thermoelectric power is enhanced for all the measured temperatures with increasing BiFeO3 content. In combination with resistivity and Seebeck coefficient data, the small polaron hopping is demonstrated to be responsible for the transport phenomena above the metal-insulator transition temperature.

  20. Band gap narrowing in ferroelectric KNbO3-Bi(Yb,Me)O3 (Me=Fe or Mn) ceramics

    Science.gov (United States)

    Pascual-Gonzalez, Cristina; Schileo, Giorgio; Feteira, Antonio

    2016-09-01

    The direct optical bandgap in ferroelectric KNbO3-Bi(Yb,Me)O3 (Me = Fe or Mn) ceramics fabricated by the solid state reaction method varies from 3.2 eV for KNbO3 down to 2.2 eV for 0.95KNbO3-0.05BiYbO3, as revealed by optical spectroscopic ellipsometry. This narrowing of bandgap is accompanied by an apparent increase of the room-temperature relative permittivity from 320 for KNbO3 to 900 for 0.95KNbO3-0.05BiYbO3. All compositions studied exhibit dielectric anomalies associated with structural phase transitions, and their ferroelectric nature is corroborated by the presence of a sharp mixed mode (at ˜190 cm-1) and by a Fano-type resonant dip in their Raman spectra.

  1. Effect of Pr doping on the superconductivity and interlayer coupling of the Bi{sub 2}Sr{sub 2-x}Pr{sub x}Ca{sub 1}Cu{sub 2}O{sub y} system

    Energy Technology Data Exchange (ETDEWEB)

    Salamati, H [Department of Physics, Isfahan University of Technology, Isfahan 84154 (Iran, Islamic Republic of); Kameli, P [Department of Physics, Isfahan University of Technology, Isfahan 84154 (Iran, Islamic Republic of); Razavi, F S [Department of Physics, Brock University, St Catharines, ON L2S 3A1 (Canada)

    2003-08-01

    We investigate the effect of Pr substitution on the superconductivity and interlayer coupling of the Bi{sub 2}Sr{sub 2}Ca{sub 1}Cu{sub 2}O{sub y} system. Magnetic and transport measurements were performed for the purposes of characterization. The superconducting transition temperature T{sub c} first increases and then decreases until it becomes zero at x = 0.6. The effective superconducting volume also decreases due to Pr substitution. From the fluctuation conductivity analysis, it is found that the interlayer coupling constant J decreases monotonically with the increase of the Pr content. This result shows that the Pr doping weakens the CuO{sub 2} interlayer coupling of the Bi2212 system due to the loss of local superconductivity in the CuO{sub 2} layers.

  2. Rietveld refinement, impedance spectroscopy and magnetic properties of Bi0.8Sr0.2FeO3 substituted Na0.5Bi0.5TiO3 ceramics

    Science.gov (United States)

    Kumari, Rekha; Ahlawat, Neetu; Agarwal, Ashish; Sanghi, Sujata; Sindhu, Monica; Ahlawat, Navneet

    2016-09-01

    We herein presented the investigation on the structural, electrical and magnetic properties of (1-x)(Na0.5Bi0.5TiO3)-x(Bi0.8Sr0.2FeO3) polycrystalline ceramic samples, with x=0.1, 0.3, 0.5 and 0.7. These samples were prepared by conventional solid state reaction method and the crystalline phase of prepared ceramics was identified with the help of X-ray diffraction pattern. Rietveld analysis of the obtained XRD data confirmed that all the synthesized samples adopt the rhombohedral crystal structure with R3c space group. Impedance spectroscopic measurements were performed on all the compositions in the frequency range 10 Hz-5 MHz to probe the electrical microstructure of polycrystalline (1-x)(Na0.5Bi0.5TiO3)-x(Bi0.8Sr0.2FeO3) ceramics, which changes significantly as a function of x (content of BSFO). A significant increase in dielectric constant has been observed with increase in BSFO concentration, which was attributed to enhancement of oxygen vacancies. Detailed study of impedance complex plane plots revealed the presence of non-Debye type relaxation for all the prepared systems and enabled us to separate the contribution from grains and grain boundaries. Equivalent circuit model (RgCPEg)(RgbCPEgb)(ReCPEe) was employed to explain the impedance data for all the prepared samples. The activation energies obtained from electric modulus as well as dc conductivity increase with increase in BSFO content, which approaches the value 1 eV and indicates an Arrehenius type thermally activated process. Remnant magnetization (Mr) and coercive field (Hc) are found to be increase with BSFO concentration.

  3. Effects of Nb doping on the microstructure, ferroelectric and piezoelectric properties of 0.7BiFeO$_3$–0.3BaTiO$_3$ lead-free ceramics

    Indian Academy of Sciences (India)

    XIAOLAN WU; LINGLING LUO; NA JIANG; XIAOCHUN WU; QIAOJI ZHENG

    2016-06-01

    Donor-doped lead-free Bi$_{0.7}$Ba$_{0.3}$(Fe$_{0.7}$Ti$_{0.3}$)$_{1−x}$Nb$_{0.66x}$O$_{3}$ + 1 mol% MnO$_2$ ceramics were prepared by a conventional oxide-mixed method and the effects of Nb-doping on microstructure, piezoelectric and ferroelectricproperties of the ceramics were investigated. All the ceramics exhibit a pure perovskite structure with rhombohedral symmetry. The grain growth of the ceramics is inhibited after the addition of Nb doping. High electricinsulation ($R = 10^9–10^{10}$ $\\Omega$·cm) and the poor piezoelectric performance and weak ferroelectricity are observed after the addition of Nb$_2$O$_5$ in the ceramics. Different from the donor effect of Pb-based perovskite ceramics, the introduction of Nb into 0.7BiFeO$_3$–0.3BaTiO$_3$ degrades the piezoelectricity and ferroelectricity of the ceramics. The Bi$_{0.7}$Ba$_{0.3}$(Fe$_{0.7}$Ti$_{0.3}$)$_{1−x}$Nb$_{0.66}$xO$_3$ + 1 mol% MnO2 ceramic with $x = 0$ exhibits the optimum piezoelectric properties with $d_{33} = 133$ pN C$^{−1}$ and $k_p = 0.29$ and high Curie temperature ($T_C = 603^{\\circ}$C).

  4. Synthesis and electrical properties of BaBiO 3 and high resistivity BaTiO 3 –BaBiO 3 ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Nitish [Oregon State Univ., Corvallis, OR (United States); Univ. of New South Wales, Sydney, NSW (Australia); Golledge, Stephen L. [Univ. of Oregon, Eugene, OR (United States); Cann, David P. [Oregon State Univ., Corvallis, OR (United States)

    2016-12-01

    Ceramics of the composition BaBiO3 (BB) were sintered in oxygen to obtain a single phase with monoclinic II2/mm symmetry as suggested by high-resolution X-ray diffraction. X-ray photoelectron spectroscopy confirmed the presence of bismuth in two valence states - 3+ and 5+. Optical spectroscopy showed presence of a direct bandgap at ~ 2.2eV and a possible indirect bandgap at ~ 0.9eV. This combined with determination of the activation energy for conduction of 0.25eV, as obtained from ac impedance spectroscopy, suggested that a polaron-mediated conduction mechanism was prevalent in BB. The BB ceramics were crushed, mixed with BaTiO3 (BT), and sintered to obtain BT–BB solid solutions. All the ceramics had tetragonal symmetry and exhibited a normal ferroelectric-like dielectric response. Using ac impedance and optical spectroscopy, it was shown that resistivity values of BT–BB were orders of magnitude higher than BT or BB alone, indicating a change in the fundamental defect equilibrium conditions. A shift in the site occupancy of Bi to the A-site is proposed to be the mechanism for the increased electrical resistivity.

  5. Stable glass-ceramic sealants for solid oxide fuel cells: Influence of Bi{sub 2}O{sub 3} doping

    Energy Technology Data Exchange (ETDEWEB)

    Goel, Ashutosh; Ferreira, Jose M.F. [Department of Ceramics and Glass Engineering, University of Aveiro, CICECO, 3810-193 Aveiro (Portugal); Pascual, Maria J. [Instituto de Ceramica y Vidrio (CSIC), Kelsen 5, Campus de Cantoblanco, 28049 Madrid (Spain)

    2010-07-15

    Diopside (CaMgSi{sub 2}O{sub 6}) based glass-ceramics in the system SrO-CaO-MgO-Al{sub 2}O{sub 3}-B{sub 2}O{sub 3}-La{sub 2}O{sub 3}-Bi{sub 2}O{sub 3}-SiO{sub 2} have been synthesized for sealing applications in solid oxide fuel cells (SOFC). The parent glass composition in the primary crystallization field of diopside has been doped with different amounts of Bi{sub 2}O{sub 3} (1, 3, 5 wt.%). The sintering behavior by hot-stage microscopy (HSM) reveals that all the investigated glass compositions exhibit a two-stage shrinkage behavior. The crystallization kinetics of the glasses has been studied by differential thermal analysis (DTA) while X-ray diffraction adjoined with Rietveld-R.I.R. analysis have been employed to quantify the amount of crystalline and amorphous phases in the glass-ceramics. Diopside and augite crystallized as the primary crystalline phases in all the glass-ceramics. The coefficient of thermal expansion (CTE) of the investigated glass-ceramics varied between (9.06-10.14) x 10{sup -6} K{sup -1} after heat treatment at SOFC operating temperature for a duration varying between 1 h and 200 h. Further, low electrical conductivity, good joining behavior and negligible reactivity with metallic interconnects (Crofer22 APU and Sanergy HT) in air indicate that the investigated glass-ceramics are suitable candidates for further experimentation as sealants in SOFC. (author)

  6. Thermoelectric sintered glass-ceramics with a Bi{sub 2}Sr{sub 2}Co{sub 2}O{sub x} phase

    Energy Technology Data Exchange (ETDEWEB)

    Lingner, Julian [Johannes Gutenberg-Universitaet Mainz, Institut fuer Physik, Mainz (Germany); SCHOTT AG, Material Development, Mainz (Germany); Funahashi, Ryoji; Combe, Emmanuel [National Institute of Advanced Industrial Science and Technology, Osaka (Japan); Letz, Martin [SCHOTT AG, Material Development, Mainz (Germany); Jakob, Gerhard [Johannes Gutenberg-Universitaet Mainz, Institut fuer Physik, Mainz (Germany)

    2015-07-15

    Glass-ceramic materials containing Bi{sub 2}Sr{sub 2}Co{sub 2}O{sub x} crystals with plate-like structures are prepared by a melting process and a subsequent sintering step after manual quenching. The chemical starting compositions of the samples are Bi{sub 2}Sr{sub 2}Co{sub 2}O{sub x} (BSC222), Bi{sub 1.8}Sr{sub 2}Co{sub 2}O{sub x} (Bi1.8) and Bi{sub 2}Sr{sub 2}Co{sub 1.7}O{sub x} (Co1.7). All three samples are p-type conductors. The electric properties of Seebeck coefficient S and electrical resistivity ρ show only a slight dependence on chemical composition. The Seebeck values increase with increasing temperature, and at T = 873 K, they reach S = 180, 176 and 167 μV/K, respectively. The electrical resistivity slightly decreases with temperature for two samples and increases for the Co1.7 sample. The thermal conductivity for all measured samples at this temperature is around κ = 0.8 W/(m K). The figure of merit ZT increases with temperature for all samples. The materials reach a ZT value of 0.03 at T = 873 K. (orig.)

  7. Dense high temperature ceramic oxide superconductors

    Science.gov (United States)

    Landingham, Richard L.

    1993-01-01

    Dense superconducting ceramic oxide articles of manufacture and methods for producing these articles are described. Generally these articles are produced by first processing these superconducting oxides by ceramic processing techniques to optimize materials properties, followed by reestablishing the superconducting state in a desired portion of the ceramic oxide composite.

  8. Effect of substitution of Ce on superconducting properties of Bi1.7Pb0.3Sr2Ca2-CeCu3O10+ system

    Indian Academy of Sciences (India)

    R R Kothawale; B N Dole; S S Shah

    2002-05-01

    We have investigated the superconducting properties of the Bi1.7Pb0.3Sr2Ca2-CeCu3O10+ system with = 0.00, 0.02, 0.04, 0.08 and 0.1 by X-ray diffraction and magnetic susceptibility. The substitution of Ce for Ca has been found to drastically change the superconducting properties of the system. X-ray diffraction studies on these compounds indicate decrease in the -parameter with increased substitution of Ce at Ca site and volume fraction of high c(2 : 2 : 2 : 3) phase decreases and low c phase increases. The magnetic susceptibility of this compound shows that the diamagnetic on set superconducting transition temperature (onset) varies from 109 K to 51 K for =0.00, 0.02, 0.04, 0.08 and 0.1. These results suggest the possible existence of Ce in a tetravalent state rather than a trivalent state in this system; that is, Ca2+ → Ce4+ replacement changes the hole carrier concentration. Hole filling is the cause of lowering c of the system.

  9. Percolation effect in thick film superconductors: Using a Bi(Pb)SrCaCuO based paste to prepare a superconducting planar transformer

    Science.gov (United States)

    Sali, Robert; Harsanyi, Gabor

    1995-01-01

    A thick film superconductor paste has been developed to study the properties of granulated superconductor materials, to observe the percolation effect and to confirm the theory of the conducting mechanism in the superconducting thick films. This paste was also applied to make a superconducting planar transformer. Due to the T(sub c) and advantageous current density properties the base of the past was chosen to be of Bi(Pb)SrCaCu) system. For contacts a conventional Ag/Pt paste was used. The critical temperature of the samples were between 110 K and 115 K depending on the printed layer thickness. The critical current density -at the boiling temperature of the liquid He- was between 200 - 300 A/sq cm. The R(T) and V(I) functions were measured with different parameters. The results of the measurements have confirmed the theory of conducting mechanism in the material. The percolation structure model has been built and described. As an application, a superconducting planar thick film transformer was planned and produced. Ten windings of the transformer were printed on one side of the alumina substrate and one winding was printed on the other side. The coupling between the two sides was possible through the substrate. The samples did not need special drying and firing parameters. After the preparation, the properties of the transformer were measured. The efficiency ans the losses were determined. Finally, some fundamental advantages and problems of the process were discussed.

  10. New superconducting oxides in the Bi-Sr-Ca-Cu-0 system: magnetic measurements and structural determination

    Energy Technology Data Exchange (ETDEWEB)

    Giordanengo, B.; Godinho, M.; Lejay, P.; De Rango, P.; Sulpice, A.; Tholence, J.L.; Tournier, R. (Centre National de la Recherche Scientifique, 38 - Grenoble (FR) Centre de Recherches sur les Tres Basses Temperatures, Grenoble, (FR)); Hewat, A.W. (Institut Max Von Laue - Paul Langevin, 38 - Grenoble (FR)); Hewat, E.A. (CEA Centre d' Etudes Nucleaires de Grenoble 38 (FR). Inst. de Recherche Technologique et de Developpement Industriel (IRDI)); Marezio, M. (AT and T Bell Lab., Murray Hill, NJ (US)); Bordet, P.; Capponi, J.J.; Chaillout, C.; Chenavas, J.J.; Hodeau, J.L.; Spieser, A.M.; Tranqui, D. (Centre National de la Recherche Scientifique, 38 - Grenoble (FR) Lab. de Cristallographie (FR))

    1988-12-01

    Detailed neutron diffraction structure analysis of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} is reported. The effects of Pb-substitution on Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} and Bi{sub 2}Sr{sub 2}CuO{sub 6} are discussed, and magnetization measurement results on the 110 K phase in the Bi-Sr-Ca-Cu-O system are given.

  11. Microstructure, dielectric and piezoelectric properties of lead-free Bi0.5Na0.5TiO3−Bi0.5K0.5TiO3−BiMnO3 ceramics

    Indian Academy of Sciences (India)

    Huabin Yang; Xu Shan; Changrong Zhou; Qin Zhou; Weizhou Li; Jun Cheng

    2013-04-01

    To improve the piezoelectric properties of Bi0.5Na0.5TiO3-based ceramics, a new perovskite-type leadfree piezoelectric (1 – – )Bi0.5Na0.5TiO3−Bi0.5K0.5TiO3−BiMnO3 system has been fabricated by a conventional solid–state reaction method and their microstructure, dielectric and piezoelectric properties have been investigated. The results of X-ray diffraction (XRD) analysis reveal that the addition of small amounts of BiMnO3 did not cause a remarkable change in crystal structure, but resulted in an evident evolution inmicrostructure. An obvious secondary phase was observed in samples with high Bi0.5K0.5TiO3 content. It is found from dielectric constant curves that low-temperature hump disappeared with increasing y and it appeared again with increasing x. The piezoelectric properties significantly increase with increasing Bi0.5K0.5TiO3 and BiMnO3 content. The piezoelectric constant and electromechanical coupling factor attain maximum values of 33 = 182 pC/N at = 0.21( = 0.01) and p = 0.333 at = 0.18 ( = 0.01), respectively.

  12. Spinon Superconductivity and Superconductivities Mediated by Spin-Waves and Phonons in Cuprates

    OpenAIRE

    Mourachkine, A.

    1998-01-01

    The disclosure of spinon superconductivity and superconductivity mediated by spin-waves in hole-doped Bi2212 cuprate raises the question about the origin of the superconductivity in other cuprates and specially in an electron-doped NCCO cuprate.

  13. Large Electric-Field Modulation of Magnetic Properties in Fe Films on BiScO3-PbTiO3 Ceramics

    Directory of Open Access Journals (Sweden)

    Jing Wang

    2010-01-01

    Full Text Available Based on the magneto-optical Kerr effect, we report the electric-field modulation of the magnetic properties in Fe/BiScO3-PbTiO3 (BSPT film-on-ceramic substrate structure. The Fe films are directly grown on the fully-poled BSPT ceramic substrates by magnetron sputtering. An electric field applied parallel to the prepolarization direction of the piezoelectric BSPT can induce a reversible increase in the coercive field Hc of about 30%, whereas an electric field antiparallel to the prepolarization direction can cause a persistent, tremendous decrease (as large as 97% in Hc, and a small reversal electric field can resume it back. The strain induced by the inverse piezoelectric effect is the primary mechanism behind. This large modulation of the coercive field by the electric field could inspire further exploration of electric-field-controlled magnetic switching in multiferroic heterostructures.

  14. Effect of Ba addition on the structural, dielectric and ferroelectric properties of Na0.5Bi0.5TiO3 ceramics

    Directory of Open Access Journals (Sweden)

    Suchanicz J.

    2015-06-01

    Full Text Available Lead-free (Na0.5Bi0.51-xBaxTiO3 (x = 0, 0.04 and 0.06 ceramics were fabricated by conventional solid phase sintering process. X-ray diffraction analysis shows that obtained specimens possess the perovskite structure. The microstructure study shows a dense structure, in good agreement with the relative density determined by the Archimedes method (above 95 %. Electric permittivity anomaly is shifted to low temperature after Ba doping of NBT. The pyroelectric and hysteresis loops measurements show that polarization and coercive field increases and decreases, respectively, after Ba doping of NBT. The obtained results are discussed in terms of ions/lattice imperfections, which create local electromechanical fields. The investigated ceramics are considered to be promising candidates for lead-free electronic materials.

  15. Effect of cerium additive and secondary phase analysis on Ag0.5Bi0.5TiO3 ceramics

    Indian Academy of Sciences (India)

    S Supriya; Antonio J Dos Santos-García; F Fernández-Martinez

    2016-02-01

    Cerium-doped silver bismuth titanate—Ag0.5Bi0.5TiO3 (ABT) ceramics have been synthesized by the high-temperature solid-state reaction method. The structure and elemental examination of the prepared ceramic was analysed by X-ray diffraction (XRD), Fourier transform infrared, scanning electron microscopy and energydispersive spectroscopy. XRD analysis showed the presence of pyrochlore structure and secondary phase when more than 5 mol% cerium was added. The impact of temperature on cerium-doped silver bismuth titanate samples was analysed by differential thermal analysis and differential scanning calorimetry. Cerium doping caused the flaky morphology comparing with undoped sample. The homogeneity of all the samples was discussed in detail by diffuse reflectance spectrum. This is the first time the reflection process is analysed for the cerium-doped ABT system to the best of our knowledge.

  16. Bright upconversion luminescence and increased Tc in CaBi{sub 2}Ta{sub 2}O{sub 9}:Er high temperature piezoelectric ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Peng Dengfeng [Functional Materials Research Laboratory, Tongji University, 1239 Siping Road, Shanghai 200092 (China); National Institute of Advanced Industrial Science and Technology, Kyushu, 807-1 Shuku, Tosu, Saga 841-0052 (Japan); Wang Xusheng; Yao Xi [Functional Materials Research Laboratory, Tongji University, 1239 Siping Road, Shanghai 200092 (China); Xu Chaonan [National Institute of Advanced Industrial Science and Technology, Kyushu, 807-1 Shuku, Tosu, Saga 841-0052 (Japan); Lin Jian; Sun Tiantuo [College of Material Science and Engineering, Tongji University, 4800 Cao' an Highway, Shanghai 201804 (China)

    2012-05-15

    Er{sup 3+} doped CaBi{sub 2}Ta{sub 2}O{sub 9} (CBT) bismuth layered-structure high temperature piezoelectric ceramics were synthesized by the traditional solid state method. The upconversion (UC) emission properties of Er{sup 3+} doped CBT ceramics were investigated as a function of Er{sup 3+} concentration and incident pump power. A bright green upconverted emission was obtained under excitation 980 nm at room temperature. The observed strong green and weak red emission bands corresponded to the transitions from {sup 4}S{sub 3/2} and {sup 4}F{sub 9/2} to {sup 4}I{sub 15/2}, respectively. The dependence of UC emission intensity on pumping power indicated that a three-photon process was involved in UC emissions. Studies of dielectric with temperature have also been carried out. Introduction of Er increased the Curie temperature of CBT, thus, making this ceramic suitable for sensor applications at higher temperatures. Because of its strong up-converted emission and increased Tc, the multifunctional high temperature piezoelectric ceramic may be useful in high temperature sensor, fluorescence thermometry, and optical-electro integration applications.

  17. Nd3+-doped TeO2-Bi2O3-ZnO transparent glass ceramics for laser application at 1.06 μm

    Science.gov (United States)

    Hu, Xiaolin; Luo, Zhiwei; Liu, Taoyong; Lu, Anxian

    2017-04-01

    The high crystallinity transparent glass ceramics based on Nd3+-doped 70TeO2-15Bi2O3-15ZnO (TBZ) compositions were successfully prepared by two-step heat treatment process. The effects of Nd2O3 content on the thermal, structural, mechanical, and optical properties of TBZ glass ceramics were studied. The incorporation of Nd2O3 enhanced the crystallization tendency in the matrix glass composition. The crystal phase and morphology of Bi2Te4O11 in the glass ceramics were confirmed by X-ray diffraction and field emission scanning electron microscopy. Due to precipitate more crystal phase, the hardness values increased from 3.21 to 3.66 GPa. Eight absorption peaks were observed from 400 to 900 nm and three emission bands appeared in the range of 850-1400 nm. With the increasing of Nd2O3 content from 0.5 to 2.5 wt%, the intensity of absorption peaks enhanced and the emission intensity increased up to 1.0 wt% and then fell down for further dopant concentration. The fluorescence decay lifetime decreased rapidly starting from 1.5 wt% Nd2O3 content due to the obvious energy migration among Nd3+. According to the extreme strong emission band around 1062 nm and the optimum Nd2O3 content (1.0 wt%), N10 glass ceramic was considered as a potential material for 1.06 μm laser applications.

  18. The effect of Al2O3 nanopowder addition on the phase formation and the superconducting properties of Bi1.6Pb0.4Sr1.9Ca2.1Cu3O10-y

    Directory of Open Access Journals (Sweden)

    A Aftabi

    2009-08-01

    Full Text Available   In this work Bi1.6Pb0.4Sr1.9Ca2.1Cu3O10-y superconducting system (Bi2223 has been prepared by solid state reaction and the effect of nanoalumina additive on the phase formation and supercoducting properties have been investigated. XRD investigations show that addition of 0.2 wt% of nanoalumina on the superconducting system improved Bi-2223 phase formation . The results show that Jc increases from 36 A/cm2 for the nanoalumina free sample to 107 A/cm2 for the sample with 0.5 wt% nanoalumina.On the other hand results show that the transition temperature (Tc of all samples is around 108 K and addition of nanoalumina has not affected Tc significantly .

  19. Photoluminescence and electrical properties of Er3+-doped Na0.5Bi4.5Ti4O15—Bi4Ti3O12 inter-growth ferroelectric ceramics

    Science.gov (United States)

    Jiang, Yalin; Jiang, Xiangping; Chen, Chao; Chen, Yunjing; Jiang, Xingan; Tu, Na

    2017-03-01

    Upconversion (UC) and electrical properties of Na0.5Bi8.5- x ErxTi7O27 (NBT-BIT- xEr, 0.00⩽ x⩽0.25) ceramics were studied. Structural analysis revealed that a single inter-growth structured phase exists in all samples and the Er3+ ion substituting for Bi3+ at the A-site increases the orthorhombic distortion. Under the 980 nm laser excitation, two characteristic green emission bands and one red emission band were situated at 527, 548 and 670 nm, corresponding to the transitions 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2, respectively. The optimal photoluminescence (PL) were found in the NBT-BIT-0.20Er sample, and the emission color transforms from green to yellowish green. Temperature dependence of fluorescence intensity ratio (FIR) for NBT-BIT-0.20Er was measured ranging from 290 to 440 K and its maximum sensitivity was calculated to be about 0.0020 K-1 at 290 K. Dielectric measurements indicated that T C slightly increased simultaneously with the decrease of tan δ. Therefore, this ceramic has potential applications for high-temperature multifunctional devices.

  20. Superconducting characterization of Ni/Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub y} superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Tokuda, T.; Hidaka, K. [Department of Electrical and Electric Engineering, Tottori University, 4-101, Koyama-Minami, Tottori 680-8552 (Japan); Kishida, S. [Department of Electrical and Electric Engineering, Tottori University, 4-101, Koyama-Minami, Tottori 680-8552 (Japan)], E-mail: kishida@ele.tottori-u.ac.jp

    2007-10-01

    We deposited non-superconducting materials, Ni metal on the surface of Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub y} (BSCCO) superconductors. Critical temperature (T{sub c}) and critical current (I{sub c}) of Ni/BSCCO specimens decreased with increasing thickness of Ni films. This indicates that the T{sub c} and the I{sub c} of the BSCCO films are degraded with a thickness of Ni. This behavior is approximately equal to that of a Ni/YBa{sub 2}Cu{sub 3}O{sub y} (YBCO) specimen, where the T{sub c} and the I{sub c} of it were dependent on rf power during Ni deposition. Therefore, the degradation of the Ni/BSCCO specimen may be due to the Ni diffusion into the BSCCO films.

  1. Field-Angle-Dependent Low-Energy Excitations around a Vortex in the Superconducting Topological Insulator CuxBi2Se3

    Science.gov (United States)

    Nagai, Yuki

    2014-06-01

    We study the quasiparticle excitations around a single vortex in the superconducting topological insulator CuxBi2Se3, focusing on a superconducting state with point nodes. Inspired by the recent Knight shift measurements, we propose two ways to detect the positions of point nodes, using an explicit formula of the density of states with Kramer-Pesch approximation in the quasiclassical treatment. The zero-energy local density of states around a vortex parallel to the c-axis has a twofold shape and splits along the nodal direction with increasing energy; these behaviors can be detected by the scanning tunneling microscopy. An angular dependence of the density of states with a rotating magnetic field on the a-b plane has deep minima when the magnetic field is parallel to the directions of point nodes, which can be detected by angular-resolved heat capacity and thermal conductivity measurements. All the theoretical predictions are detectable via standard experimental techniques in magnetic fields.

  2. Optimization on dielectric properties of Y2Ti2O7 ceramics with Bi2O3-Nd2O3-Nb2O5 co-doping

    Institute of Scientific and Technical Information of China (English)

    DING Jiayu; WANG Zhefei; GONG Zhijie; XIAO Yuan; WANG Lixi; ZHANG Qitu

    2011-01-01

    The present work aimed to explore a kind of microwave dielectric materials with middle-permittivity,high Qf,near-zero τf,and lower sintering temperature.A series of Y2Ti2O7 microwave dielectric ceramics were synthesized by conventional solid-state method.For improving the dielectric properties of Y2Ti2O7 systerm,Bi2O3,Nd2O3 and Nb2O5 were added and their effects on phase composition,microstructure,and dielectric properties at microwave frequencies were investigated by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM).The queuing score method for multi-target orthogonal design was used to obtain the optimum prescription.The results showed that the Y2Ti2O7 ceramics with 8 wt.% Bi2O3 and 1 mol.% Nd2O3-Nb2O5 were well sintered at 1350 ℃,exhibiting excellent dielectric characteristics,i.e.εr≈76,Qf≈18980 GHz,τf=+25.5 ppm/℃.

  3. Non-Ohmic conduction in In{sub 2}O{sub 3}–Bi{sub 2}O{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Glot, A.B., E-mail: alexglot@mixteco.utm.mx [Universidad Tecnológica de la Mixteca, Huajuapan de León, Oaxaca 69000 (Mexico); Mazurik, S.V. [Dniepropetrovsk National University, Dniepropetrovsk 49010 (Ukraine)

    2013-11-01

    The semiconductor In{sub 2}O{sub 3}–Bi{sub 2}O{sub 3} ceramics exhibit unusual behaviour: The current quasi-saturation (current limiting) in dc current–voltage characteristic is accompanied by low-frequency (∼1 Hz) current oscillations. In this paper some electrical properties of In{sub 2}O{sub 3}–Bi{sub 2}O{sub 3} ceramics are studied and a mechanism of non-Ohmic conduction in this material is suggested. The electrical conduction is controlled by the grain-boundary potential barriers. Assuming that the barrier heights at different grain boundaries in a sample are not identical, the current quasi-saturation is explained qualitatively by capture of electrons at the interface states and respective increase in the height of key barriers. A mechanism of current oscillations is related to the current quasi-saturation. An increase in the height of key barriers leads to a raise of the voltage drop at these barriers and to Joule heating of barrier regions followed by decrease in the barrier height. The suggested mechanism of non-Ohmic conduction is confirmed by the obtained experimental data.

  4. Oxygen sorption-desorption behavior and superconductivity of Bi-based oxide superconductor (2212 phase). Bi-kei sankabutsu chodendotai (2212 so) no sanso shudacchaku kyodo to chodendo tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Deshimaru, Y.; Otani, T.; Shimizu, Y.; Miura, N.; Yamazoe, N. (Kyushu Univ., Fukuoka (Japan). Graduate School of Engineering Sciences)

    1991-09-01

    Authors have researched on a very small quantity of oxygen sorption-desorption behavior of Bi-based 2223 phase specimen (Pb added) by means of TPD method, and have examined correlation between the desorpted quantity of oxygen and critical temperature T {sub c}. In this paper, correlation among oxygen content volume change of 2212 phase specimen and crystal structure and superconductive characteristics were examined, by researching oxygen sorption-desorption behavior using TPD method same as the last report. Further, Pb add effects were also researched using 2212 phase specimen, which was changed the composition ratio of Sr and Ca. As a result, in each case of 4 specimens of Bi {sub 2 {minus} x} Pb {sub x} Sr {sub 2 {minus} y} Ca {sub 1+y} Cu {sub 2} O {sub 8+{delta}}, (x,y) = (0, 0), (0, 0.8), (0.2, 0), (0.2, 0.8), it could be found that very small quantity of oxygen about 2 {approximately} 3 {times} 10 {sup {minus} 5} mol/g would be sorpted/desorpted reversibly under less than 600 {degree} C. Moreover, in case of Pb added specimen, it could be clarified that hole concentration was about 1 {times} 10 {sup {minus} 5} mol/g in converted to the oxygen quantity higher than the case of not added one. 29 refs., 8 figs., 1 tab.

  5. Variation of Piezoelectric properties and mechanisms across the relaxor-like/Ferroelectric continuum in BiFeO3- (K0.5Bi0.5)TiO3-PbTiO3 ceramics.

    Science.gov (United States)

    Bennett, James; Shrout, Thomas R; Zhang, Shujun; Owston, Heather E; Stevenson, Tim J; Esat, Faye; Bell, Andrew J; Comyn, T P

    2015-01-01

    1- x - y)BiFeO3-x(K0.5Bi0.5)TiO3-yPbTiO3 (BFKBT- PT) piezoelectric ceramics were investigated across the compositional space and contrasted against the xBiFeO3- (1-x)(K0.5Bi0.5)TiO3 (BF-KBT) system, whereby a range of relaxor-like/ferroelectric behavior was observed. Structural and piezoelectric properties were closely related to the PbTiO3 concentration; below a critical concentration, relaxor-like behavior was identified. The mechanisms governing the piezoelectric behavior were investigated with structural, electrical, and imaging techniques. X-ray diffraction established that longrange non-centrosymmetric crystallographic order was evident above a critical PbTiO3 concentration, y > 0.1125. Commensurate with the structural analysis, electric-field-induced strain responses showed electrostrictive behavior in the PbTiO3-reduced compositions, with increased piezoelectric switching in PbTiO3-rich compositions. Positive-up-negative-down (PUND) analysis was used to confirm electric-field-induced polarization measurements, elucidating that the addition of PbTiO3 increased the switchable polarization and ferroelectric ordering. Piezoresponse force microscopy (PFM) of the BF-KBT-PT system exhibited typical domain patterns above a critical PbTiO3 threshold, with no ferroelectric domains observed in the BF-KBT system in the pseudocubic region. Doping of BiFeO3-PbTiO3 has been unsuccessful in the search for hightemperature materials that offer satisfactory piezoelectric properties; however, this system demonstrates that the partial substitution of alternative end-members can be an effective method. The partial substitution of PbTiO3 into BF-KBT enables long-range non-centrosymmetric crystallographic order, resulting in increased polar order and TC, compared with the pseudocubic region. The search for novel high-temperature piezoelectric ceramics can therefore exploit the accommodating nature of the perovskite family, which allows significant variance in chemical and physical

  6. International round robin test of the retained critical current after double bending at room temperature of Ag-sheathed Bi-2223 superconducting wires

    Science.gov (United States)

    Yamada, Y.; Nishijima, G.; Osamura, K.; Shin, H. S.; Goldacker, W.; Breschi, M.; Ribani, P.

    2016-02-01

    An international round robin test was carried out in order to establish a test method for retained critical current after double bending at room temperature of Ag-sheathed Bi-2223 superconducting wires. Tests for commercial Bi-2223 tape were conducted by six laboratories using the same guidelines. The standard uncertainties (SUs) of measurands were evaluated for these four quantities: I C0, I C/I C080, I C/I C060, I C/I C050, where, I C0 is initial critical current and I C /I C0XX is critical current after XX mm bending. Using an F test to determine where the most scatter was generated in the test results it was found that the greatest scatter in the normalized critical current measurements came from inter-laboratory scatter. In a type-B uncertainty evaluation, the major contribution was from the bending diameter and measuring temperature. The relative SU tended to increase as the bending diameter decreased. A specific mandrel diameter corresponding to a retained critical current of 95% could be determined with a relative SU of 1.3%. In order to reduce the overall scatter, the temperature difference between the critical current measurements before and after bending should be small.

  7. Superconducting and mechanical properties of the bulk Bi(pb)SCCO system prepared via solid state and ammonium nitrate precipitation methods

    Energy Technology Data Exchange (ETDEWEB)

    Safran, S., E-mail: safran@science.ankara.edu.tr [Ankara University, Faculty of Science, Department of Physics, Tandoğan, Ankara 06100 (Turkey); Center of Excellence for Superconductivity Research, 50 Year Campus, Golbaşı, Ankara (Turkey); Kılıçarslan, E.; Ozturk, H. [Ankara University, Faculty of Science, Department of Physics, Tandoğan, Ankara 06100 (Turkey); Center of Excellence for Superconductivity Research, 50 Year Campus, Golbaşı, Ankara (Turkey); Alp, M. [Center of Excellence for Superconductivity Research, 50 Year Campus, Golbaşı, Ankara (Turkey); Akdogan, M. [Center of Excellence for Superconductivity Research, 50 Year Campus, Golbaşı, Ankara (Turkey); Abant İzzet Baysal University, Department of Physics, Bolu (Turkey); Asikuzun, E.; Ozturk, O. [Kastamonu University, Department of Physics, Kastamonu (Turkey); Kastamonu University, Research and Application Center, Kastamonu (Turkey); Kılıç, A. [Ankara University, Faculty of Science, Department of Physics, Tandoğan, Ankara 06100 (Turkey); Center of Excellence for Superconductivity Research, 50 Year Campus, Golbaşı, Ankara (Turkey)

    2015-09-01

    We have investigated the effect of preparation method on superconducting and mechanical properties of Bi(Pb)-2223 bulk samples using Bi{sub 1.85}Pb{sub 0.35}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10±y} stoichiometry. Solid-state reaction and ammonium nitrate precipitation methods have been used for fabrication of the bulk samples. In addition, the effect of annealing time on BSCCO samples have been studied. Structural, electrical, magnetic and microhardness analyses of samples are performed by the X-ray powder diffraction (XRD), the Scanning Electron Microscopy (SEM), DC resistivity, AC susceptibility and Vickers microhardness test. The critical transition temperature, phase purity, surface morphology and crystallinity of the prepared bulk samples are compared with each other. Elasticity (E), brittleness (B{sub i}), fracture toughness (K{sub IC}) and yield strength (Y) values are also determined according to annealing time, applied load and production parameters of materials.

  8. Structure and superconductivity in (Bi{sub 0.35}Cu{sub 0.65})Sr{sub 2}YCu{sub 2}O{sub 7} and related materials

    Energy Technology Data Exchange (ETDEWEB)

    Jennings, R.A.; Williams, S.P.; Greaves, C. [Univ. of Birmingham (United Kingdom)

    1994-12-31

    The recently reported (Bi/Cu)Sr{sub 2}YCu{sub 2}O{sub 7} phase has been studied by time of flight powder neutron diffraction. The proposed 1212 structure has been confirmed and refinements have shown the oxygen in the (Bi/Cu)O layer is displaced by 0.78{angstrom} from the ideal (1/2,1/2,0) site (P4/mmm space group) along (100). Bond Valence Sum calculations have suggested oxidation states of Bi{sup 5+} and Cu{sup 2+} for the cations in the (Bi/Cu)O layers. The material is non-superconducting and all attempts to induce superconductivity have been unsuccessful. Work on the related material (Ce/Cu)Sr{sub 2}YCu{sub 2}O{sub y} has shown the ideal Ce content to be 0.5 Ce per formula unit. The introduction of Ba (10%) onto the Sr site dramatically increases phase stability and also induces superconductivity (62K).

  9. PHASE EVOLUTION AND MICROWAVE DIELECTRIC PROPERTIES OF (Li0.5Bi0.5)(W1-xMox)O4(0.0 ≤ x ≤ 1.0) CERAMICS WITH ULTRA-LOW SINTERING TEMPERATURES

    Science.gov (United States)

    Zhou, Di; Guo, Jing; Yao, Xi; Pang, Li-Xia; Qi, Ze-Ming; Shao, Tao

    2012-11-01

    The (Li0.5Bi0.5)(W1-xMox)O4(0.0 ≤ x ≤ 1.0) ceramics were prepared via the solid state reaction method. The sintering temperature decreased almost linearly from 755°C for (Li0.5Bi0.5)WO4 to 560°C for (Li0.5Bi0.5)MoO4. When the x≤0.3, a wolframite solid solution can be formed. For x = 0.4 and x = 0.6 compositions, both the wolframite and scheelite phases can be formed from the X-ray diffraction analysis, while two different kinds of grains can be revealed from the scanning electron microscopy and energy-dispersive X-ray spectrometer results. High performance of microwave dielectric properties were obtained in the (Li0.5Bi0.5)(W0.6Mo0.4)O4 ceramic sintered at 620°C with a relative permittivity of 31.5, a Qf value of 8500 GHz (at 8.2 GHz), and a temperature coefficient value of +20 ppm/°C. Complex dielectric spectra of pure (Li0.5Bi0.5)WO4 ceramic gained from the infrared spectra were extrapolated down to microwave range, and they were in good agreement with the measured values. The (Li0.5Bi0.5)(W1-xMox)O4(0.0 ≤ x ≤ 1.0) ceramics might be promising for low temperature co-fired ceramic technology.

  10. Electrocaloric effect and energy storage in lead free Gd0.02Na0.48Bi0.5TiO3 ceramic

    Science.gov (United States)

    Zannen, M.; Lahmar, A.; Kutnjak, Z.; Belhadi, J.; Khemakhem, H.; El Marssi, M.

    2017-04-01

    The electrocaloric effect (EC) was investigated in the ferroelectric lead-free Na1/2(Bi0.98 Gd0.02)1/2TiO3 (GdNBT) ceramics. A pure perovskite structure was observed by the X-ray diffraction in GdNBT ceramics synthesized by a solid-state reaction method. Dielectric measurements revealed the existence of different ferroelectric and antiferroelectric transformations in this material. Based on the temperature dependence of P-E loops, reversible electrocaloric temperature changes of about ΔT = 0.75 K at the electric field of 90 kV/cm and the EC responsivity ΔT/ΔE ≈ 0.08 × 10-6 K m V-1 were obtained in the GdNBT ceramics. The energy-storage density W = 0.85 J cm-3 and the associated efficiency (η = 65%) at 413 K were determined from the P-E loops data. The simultaneous existence of EC responsivity and energy-storage density makes GdNBT very promising lead-free material and opens a great potential for its application in electronic devices.

  11. Superconductivity of reduction-treated ceramic material of Pr{sub 2}Ba{sub 4}Cu{sub 7}O{sub 15-{delta}} mixed with the related structure phases

    Energy Technology Data Exchange (ETDEWEB)

    Hagiwara, M. [Department Comprehensive Sciences, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585 (Japan)], E-mail: hag@kit.ac.jp; Tanaka, S.; Shima, T.; Gotoh, K. [Department Comprehensive Sciences, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585 (Japan); Kanda, S.; Saito, T.; Koyama, K. [University of Tokushima, Tokushima 770-8502 (Japan)

    2008-09-15

    Superconductivity caused by oxygen reduction treatment for sintered Pr{sub 2}Ba{sub 4}Cu{sub 7}O{sub 15-{delta}} (Pr247) synthesized using citrate pyrolysis precursor method is examined experimentally. The sintered sample tends to be heterogeneous structure including Pr124 phase and stacking fault structure rich in CuO single chains. In this work, such a heterogeneous sample and nearly pure phase one were prepared, and the electric conductive behaviors were examined comparatively for various reduction grade sample series. In enough reduced stages, superconductivity with onset temperature 25-28 K was observed for both heterogeneous and purer samples. At transition process by the reduction, superconductivity of the heterogeneous samples can arise from lower oxygen-reduction% than purer Pr247 material. The results may possibly suggest superconductivity by CuO double chains besides Pr247 crystal in our heterogeneous ceramic system.

  12. Growth and superconducting properties of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} {sub +} {sub δ} thin films incorporated with iridate nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    De Vero, Jeffrey C.; Hwang, Inwoong; Shin, Hyeonseop; Song, Jong Hyun [Department of Physics, Chungnam National University, Daejeon, 305-764 (Korea, Republic of); Santiago, Alvin Carl; Sarmago, Roland V. [National Institute of Physics, University of the Philippines, Diliman, 1101 (Philippines); Lee, Doopyo [Department of Physics, Pohang University of Science and Technology, Pohang, 790-784 (Korea, Republic of); Chang, Jungwon [Department of Display and Semiconductor Physics, Korea University, Sejong Campus, Sejong, 339-700 (Korea, Republic of); Korea Research Institute of Science and Standards, Daejeon, 305-340 (Korea, Republic of); Kim, Jinhee [Korea Research Institute of Science and Standards, Daejeon, 305-340 (Korea, Republic of)

    2014-08-15

    Iridate nanoparticle AIrO{sub 3} (A = Sr, Ba) incorporated Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} {sub +} {sub δ} (Bi-2212) thin films were successfully grown using pulsed laser deposition with post-growth ex situ heat treatment. Nanosized particles of SrIrO{sub 3} (Sr-iridate) and BaIrO{sub 3} (Ba-iridate) were deposited on top of MgO (100) substrate, followed by Bi-2212 layers to investigate their effects on the physical and superconducting properties of Bi-2212 thin films. The number of laser pulses was changed from 450 to 1800 to control the density of iridates in the Bi-2212 matrix. The composite film is then partial-melted at 890 C for 15 min and annealed at 850 C for 5 h in ambient air. Scanning electron microscopy shows that the surfaces of thin films with iridates are more compact with minimal voids and porosity than those of pure Bi-2212 thin films. Both types of iridate incorporation suppress T{sub c-zero} of Bi-2212 thin films. Incorporating Sr-iridate in the Bi-2212 strongly affects T{sub c-zero} than those with Ba-iridate at low density. However, both iridate incorporations result in the expansion of the c-axis lattice constant and variation of Bi/Sr ratio of Bi-2212 films. On the other hand, we observed improvement of the activation energy, U{sub 0}, as well as the self-field critical current density, J{sub c}(0), of Bi-2212 films with incorporated iridates even with suppressed T{sub c-zero}. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Processing Bi-Pb-Sr-Ca-Cu-O superconductors from amorphous state

    Science.gov (United States)

    Chiang, C. K.; Freiman, S. W.; Wong-Ng, W.; Hwang, N. M.; Shapiro, A. J.; Hill, M. D.; Cook, L. P.; Shull, R. D.; Swartzendruber, L. J.; Bennett, L. H.

    1990-01-01

    Researchers produced superconducting ceramics of the Bi-Pb-Sr-Ca-Cu-O system started from a glass. To form the glass, the mixed oxide powder was melted at 1200 C in air. The liquid was quenched rapidly by pouring it onto an aluminum plate and rapidly pressing with another plate. The quenched compound was in the form of black amorphous solid, whose x-ray powder pattern has no crystalline peaks. After heat treatment at high temperatures, the glass crystallized into a superconductor. The crystalline phases in the superconductor identified using x-ray diffraction patterns. These phases were that associated with the superconducting phases of T(sub c) = 80 K (Bi2Ca1Sr2Cu2Ox) and of T(sub c) = 110 K (Bi2Ca2Sr2Cu3Ox). The dc resistivity and the ac susceptibility of these superconductors were studied.

  14. Structural and dielectric studies of Bi (Ni0.45Ti0.45Fe0.10) O3 ceramics

    Science.gov (United States)

    Kumar, Nitin; Shukla, Alok; Choudhary, R. N. P.; Behera, C.

    2016-05-01

    In the present investigation, a solid solution of BiFeO3 and NiTiO3 i.e., Bi(Ni0.45Ti0.45Fe0.10)O3 (abbreviation is BNTF) have been synthesized using a solid-state reaction technique. Structural and dielectric properties of BNTF ceramics have been studied in details to understand their properties. Preliminary X-ray diffraction analysis confirm the formation of a new system, which is different from that of its parent compounds. Substitution of a small amount of NiTiO3 into BiFeO3 enhances dielectric and ferroelectric properties, and reduces electrical leakage current or tangent loss. It was shown by XRD that at room temperature structure of the compound is of single-phase with tetragonal symmetry. Some electrical characteristics (dielectric constant and loss) studied over a wide frequency (1 kHz-1 MHz) and temperature (25-400°C) ranges have provided many more interesting information useful for devices.

  15. The spatial distribution of temperature and oxygen deficiency in spark-plasma sintered superconducting Bi-based materials

    Energy Technology Data Exchange (ETDEWEB)

    Govea-Alcaide, E.; Pérez-Fernández, J.E. [Departamento de Ciencias Básicas, Facultad de Ciencias Técnicas, Universidad de Granma, Apdo. 21, P.O. Box 85100, Bayamo (Cuba); Machado, I.F. [Departamento de Engenharia Mecatrônica e Sistemas Mecânicos, Escola Politécnica, Universidade de São Paulo, 05508-900 São Paulo, SP (Brazil); Jardim, R.F., E-mail: rjardim@if.usp.br [Instituto de Física, Universidade de São Paulo, CP 66318, 05315-970 São Paulo, SP (Brazil)

    2014-12-15

    Pre-reacted powders of (Bi–Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+δ} (Bi-2223) were consolidated by using the spark plasma sintering (SPS) technique under vacuum and at different consolidate temperatures T{sub D}. X-ray diffraction patterns revealed that the dominant phase in all SPS samples is the Bi-2223 phase, but traces of the Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 10+x} (Bi-2212) phase were identified. We have found that the transport properties of SPS samples depend on their oxygen content because the SPS process is performed under vacuum. Simulations by using the finite element method (FEM) were performed for determining the actual temperature in which powders are consolidated. From these results we have inferred that SPS samples are oxygen deficient and such a deficiency is more marked near the grain boundaries, suggesting the occurrence of grains with core–shell morphology. We also argued that the width of the shell depends on the consolidation temperature, a feature corroborated by the FEM simulations.

  16. Preparation of dense nanocrystalline Bi{sub 2}O{sub 3}-HfO{sub 2}-Y{sub 2}O{sub 3} ceramic by microwave plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Zhen Qiang [Nano-Science and Nano-Technology Research Center, School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China)]. E-mail: qzhen@staff.shu.edu.cn; Vannier, Rose Noelle [Laboratoire de Cristallochimie et Physicochimie du Solide, UPRESA-CNRS 8012 ENSCL-USTL, BP 108, 59652 Villeneuve d' Ascq Cedex (France); Kale, Girish M. [Institute for Materials Research, University of Leeds, Leeds LS2 9JT (United Kingdom)

    2007-01-25

    Processing of nanocrystalline Bi{sub 2}O{sub 3}-HfO{sub 2}-Y{sub 2}O{sub 3} ceramic having high density has been investigated and reported in this paper. Nanopowders of mixed bismuth oxide, hafnia and yttrium oxide have been prepared by a reverse titration chemical coprecipitation from Bi{sup 3+}, Hf{sup 4+} and Y{sup 3+} containing aqueous solution. The high density, nanocrystalline Bi{sub 2}O{sub 3}-HfO{sub 2}-Y{sub 2}O{sub 3} ceramic has been synthesized by microwave plasma sintering. The XRD results of grain growth behavior indicates that growth of both {delta}-Bi{sub 2}O{sub 3} and c-HfO{sub 2} crystallites obeys the parabolic rate law, expressed as (D-D {sub 0}){sup 2} = Kt, during sintering process. After sintering at 700 deg. C for 60 min, the relative density of the samples sintered by microwave plasma has been found to be greater than 97%, and the samples exhibit considerably finer microstructure with an average size between 60 and 70 nm and equiaxed morphology and better density comparing with that of samples sintered by conventional pressureless sintering. In addition, mechanical properties of nanocrystalline Bi{sub 2}O{sub 3}-HfO{sub 2}-Y{sub 2}O{sub 3} ceramic has been improved greatly compareing with nanocrystalline Bi{sub 2}O{sub 3}-Y{sub 2}O{sub 3} ceramic.

  17. Effects of out-of-plane disorder on the superconductivity of Bi{sub 2}Sr{sub 2-x}La{sub x}CuO{sub 6+{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Roehler, Juergen; Trabant, Christoph; Frielingsdorf, Johanna; Djemour, Rabia [Universitaet Koeln, 50937 Koeln (Germany); Martovitsky, Victor [Lebedev-Institute, 119991 Moscow (Russian Federation); Dudy, Lenart; Dwelk, Helmut; Krapf, Alica [Humboldt Universitaet Berlin, 12489 Berlin (Germany)

    2008-07-01

    The effects of out-of-plane substitutional order/disorder on cuprate superconductivity remains to a large extent an unresolved issue. We have investigated the connection between superconductivity and the lattice effects arising from the heterovalent doping of Bi{sub 2}Sr{sub 2-x}La{sub x}CuO{sub 6+{delta}}, x = 0.8-0.1. Decreasing lanthanum content tunes the compound through the entire underdoped and overdoped regimes. Cu-K and La- K EXAFS served as local structural probes, and single crystal X-ray diffraction for the determination of the basic unit cell, and the symmetry of the supercell. The oxygen atoms in the CuO{sub 2} planes were found significantly disordered, dependent on doping, and to exhibit minimum disorder around x{sub opt}=0.33. But the degree of substitutional disorder in the out-of-plane La environment turned out independent on the concentration of the La dopants, the superstructure symmetry, and the crystal growth parameters, whereas T{sub c} depends sensitively on them. No evidence was found for possible concentration dependent site changes of the La dopant from the nominal Sr to the Bi sites. We discuss the probably crucial role of the interstitial oxygen atoms for the superconducting properties of the Bi{sub 2}Sr{sub 2-x}La{sub x}CuO{sub 6+{delta}} system.

  18. Enhanced magnetic response in single-phase Bi0.80La0.15A0.05FeO3-δ (A=Ca, Sr, Ba) ceramics

    Science.gov (United States)

    Sharma, Poorva; Kumar, Ashwini; Varshney, Dinesh

    2015-10-01

    Single phase Bi0.80La0.15A0.05FeO3-δ (A=Ca, Sr, Ba) dense ceramics were synthesized via solid state reaction method. Structural studies through X-ray diffraction shows that all prepared ceramics crystallized in a rhombohedrally (R 3 barC)distorted BiFeO3 structure with compressive lattice distortion induced by the rare earth (La3+) ion and divalent co-doping at the Bi-site for the Raman study. Scanning electron micrograph of the compounds showed the uniform distribution of grains on the sample surface with high density. A large ferromagnetic hysteresis loop is observed for La/Ba co-doped BiFeO3 as compared with BiFeO3 prepared under similar conditions, with saturation magnetization of 6.85 emu/g and remnant magnetization of 2.72 emu/ g at 300 K. Clear ferromagnetic ground state was observed in Bi0.80La0.15Ba0.05FeO3 and weak ferromagnetism in BLCFO and BLSFO samples. Dielectric constant and dielectric loss were found to decrease with increase in frequency for all the compounds. These improved properties of La/Ba co-doped BFO demonstrate the possibility of enhancing the magnetic applicability and makes very promising for industrial applications such as new devices in information storage.

  19. Pressure and temperature dependent up-conversion properties of Yb3+-Er3+ co-doped BaBi4Ti4O15 ferroelectric ceramics

    Institute of Scientific and Technical Information of China (English)

    戚兴国; 随志磊; 邓宇航; 代如成; 王中平; 张增明; 丁泽军

    2014-01-01

    Yb3+ and Er3+ co-doped BaBi4Ti4O15 (BBT) ceramic samples showed brighter up-conversion photoluminescence (UC-PL) under excitation of 980 nm. The monotonous increase of fluorescence intensity ratio (FIR) from 525 to 550 nm with temperature showed that this material could be used for temperature sensing with the maximum sensitivity to be 0.0046 K-1 and the energy dif-ference was 700 cm-1. Moreover, the sudden change of red and green emissions around 400 ºC might imply a phase transition. With increasing pressure up to 4 GPa, the PL intensity decreased but was still strong enough. These results illustrated the wide applications of BBT in high temperature and high pressure conditions.

  20. Energy storage property in lead free gd doped Na1/2Bi1/2TiO3 ceramics

    Science.gov (United States)

    Zannen, Moneim; Lahmar, Abdelilah; Khemakhem, Hamadi; El Marssi, Mimoun

    2016-11-01

    The Effect of Gadolinium ion incorporation on structure, dielectric and ferroelectric properties of lead-free Na1/2Bi1/2TiO3 (NBT) ceramic was investigated. X-ray diffraction allowed the identification of a pure phase isostructural to NBT. Dielectric measurements showed more pronounced anomalies in the range of depolarization temperature when Gd was added. Antiferroelectric-like behavior with a double pinched hysteresis loop was observed versus temperature in the doped phase. The energy-storage density (W) was calculated using the P-E loops data and was found to vary from 0.45 J cm-3 at room temperature to 0.85 J cm-3 at 413 K, which is promising for energy storage application.

  1. Piezoelectric properties of low loss and high Curie temperature (Bi, La)FeO_3-Pb(Ti, Mn)O_3 ceramics with Mn doping

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    Piezoelectric ceramics of 0.6(Bi0.9La0.1)FeO3-0.4Pb(Ti1-xMnx)O3 (BLF-PTM) for x=0, 0.01, 0.02, and 0.03 were prepared by sol-gel process combined with a solid-state reaction method. The tan? for BLF-PTM of x=0.01 is just 0.006 at 1 kHz, drastically decreasing by using Mn dopants. The TC increases to 490 ℃ for BLF-PTM of x=0.02. Furthermore, Mn modification effectively enhances the poling state and the piezoelectric properties of BLF-PTM. The kp, Qm, d33, and g33 of 0.34, 403, and 124 pC1·N-1 and 37×10-3 Vm·...

  2. Correlation between temperature-dependent permittivity dispersion and depolarization behaviours in Zr4+-modified BiFeO3–BaTiO3 piezoelectric ceramics

    Indian Academy of Sciences (India)

    Weidong Zeng; Changrong Zhou; Jianrong Xiao; Jiafeng Ma

    2015-12-01

    The correlation between permittivity frequency dispersion and depoling process upon heating was investigated in Zr4+-modified 0.75BiFeO3–0.25BaTiO3 (BF–BZT) ceramics. The temperature-dependent permittivity r() and the piezoelectric coefficient 33 for poled samples were measured under heating conditions to clarify the depolarization mechanism. The results indicate that the poling temperature plays a crucial role in the domains' alignment process, as expected. The temperature-dependent permittivity frequency dispersion and depolarization behaviours may have same origin. The aligned domains' break up into random state/nanodomains at depoling temperature ( d), which causes strong frequency dependence of the permittivity, simultaneously, induces the loss of piezoelectricity. It suggests that the temperature-dependent permittivity measurements method is a simple way to determine the depolarization temperature.

  3. Structural, dielectric and magnetic properties of Bi0.8Ba0.2Fe0.6Mn0.4O3 ceramic

    Science.gov (United States)

    Rangi, Manisha; Sanghi, S.; Agarwal, A.; Kaswan, K.; Jangra, S.; Singh, O.

    2016-05-01

    Polycrystalline Bi0.8Ba0.2Fe0.6Mn0.4O3 ceramic was synthesized via conventional two stage solid state reaction method. The crystal structure is examined via powder x-ray diffraction and Rietveld refinement revealed that the sample has a rhombohedral crystal structure (space group R3c). The dielectric response of the sample was analyzed in the frequency range 10 Hz to 5 MHz at different temperature. The values of dielectric constant (ɛ') and dielectric loss factor (tan δ) increases with increasing temperature at different frequencies which may be the result of increase in the number of charge carriers and their mobilities due to the thermal activation. M-H hysteresis loop was recorded at room temperature up to a field of 15 kOe which shows that there is slightly enhancement in magnetization with co-doping.

  4. Spectral weight changes at the superconducting transition of Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8+. delta

    Energy Technology Data Exchange (ETDEWEB)

    Dessau, D.S.; Shen, Z.X.; Wells, B.O.; Spicer, W.E. (Stanford Univ., CA (United States). Stanford Electronics Labs.); Arko, A.J. (Los Alamos National Lab., NM (United States))

    1991-01-01

    An overview of our gap studies in high-{Tc} superconductors is presented for the workshop on Fermiology of high-{Tc}'s. The work is centered on the study of single crystal Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}}. In a conventional BCS superconductor, a superconducting gap {Delta} is formed when the near Fermi edge electrons condense to form Cooper pairs at low temperatures. As the material goes superconducting the density of states is modified such that the spectral intensity in the region from the Fermi energy down to an energy {Delta} is transferred to a regions just below {Delta}. While this spectral weight transfer has in the past been studied with tunneling spectroscopy, the size of the gap as well as improvements in our instrument resolution allow us now to study it with photoelectron spectroscopy. We have found that as the sample goes superconducting, not only is there spectral weight transfer from the gap region as in BCS theory, but along the {Gamma}-M direction there is also some spectral weight transfer from higher binding energies resulting in a dspectral dip at about {minus}90 meV relative E{sub F}. The total spectral weight decreases along the {Gamma}-M direction, but actually increases along the {Gamma}-X direction. This temperature dependent spectral transfer is discussed in terms of (1) a two to three dimensional phase transition from RVB theory; (2) a manifestation of the electron-boson interaction in the form of {alpha}{sup 2}F oscillations; and (3) conformity with the theory of Van Hove singularities. The latter are particularly attractive in that there are several other observations possibly explained by them: (1) the observation that the magnitude of the gap is anisotropic in the a-b plane; (2) the observation that for overdoped samples the magnitude of D appears to fall off faster then {Tc}. 25 refs., 8 figs., 1 tab.

  5. Quenching effects for piezoelectric properties on lead-free (Bi1/2Na1/2)TiO3 ceramics

    Science.gov (United States)

    Muramatsu, Hiroki; Nagata, Hajime; Takenaka, Tadashi

    2016-10-01

    Lead-free ferroelectric and piezoelectric ceramics, (Bi0.5Na0.5)TiO3 (BNT), were fabricated by a quenching procedure after sintering, and then their electrical properties were investigated with the aim to increase their depolarization temperature T d. From the measurement of the temperature dependence of dielectric properties, T d increased with increasing quench temperature. The T d of a BNT sample quenched from 1100 °C was 223 °C, which was almost 50 °C higher than that prepared by the ordinary cooling process. From the measurement of P-E hysteresis loops, both the remanent polarization P r and the coercive field E c of BNT samples prepared by ordinary firing were almost the same as those quenched from 1100 °C. Additionally, from the measurements by a resonance-antiresonance method, the electromechanical coupling factor k 33 of ordinarily fired BNT was 0.45, and that of the quenched BNT was 0.46. From these results, it is clarified that the quenching procedure is an effective way to increase the T d of BNT ceramics without deteriorating ferroelectric and piezoelectric properties.

  6. Study of (Bi{sub 2}O{sub 3})(Ba{sub x}Mo{sub 1-x}O{sub 3}) polycrystalline ceramic as relaxor ferroelectric

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Paramjeet; Agarwal, Ashish [Department of Applied Physics, Guru Jambheshwar University of Science and Technology, Hisar-125001, Haryana (India); Sanghi, Sujata, E-mail: sutkash@yahoo.com [Department of Applied Physics, Guru Jambheshwar University of Science and Technology, Hisar-125001, Haryana (India); Singh, Navneet [Department of Applied Physics, Guru Jambheshwar University of Science and Technology, Hisar-125001, Haryana (India); Khasa, Satish [Department of Physics, Deenbandhu Chhotu Ram University of Science and Technology, Murthal, Sonipat-131093, Haryana (India)

    2012-12-15

    Solid solutions of bismuth layered (Bi{sub 2}O{sub 3})(Ba{sub x}Mo{sub 1-x}O{sub 3}) (0.2{<=}x{<=}0.8, x is in step of 0.2) ceramics were prepared by conventional solid-state reaction of the constitutive oxides at optimized temperatures with a view to study its electrical properties. Powder X-ray diffraction has been employed for physical characterization and an average grain size of {approx}16 to 22 nm was obtained. XRD study reveals the single phase structure of the samples. Dielectric properties such as dielectric constant ({epsilon} Prime ), dielectric loss (tan{delta}) and ac electrical conductivity ({sigma}{sub ac}) of the prepared ceramics sintered at various temperatures in the frequency range 10{sup 1}-10{sup 7} Hz have been studied. A strong dispersion observed in the dielectric properties shows the relaxor type behavior of the ceramic. The presence of maxima in the dielectric permittivity spectra indicates the ferroelectric behavior of the samples. Impedance plots (Cole-Cole plots) at different frequencies and temperatures were used to analyze the electric behavior. The value of grain resistance increases with the increase in Ba ion concentration. The conductivity mechanism shows a frequency dependence, which can be ascribed to the space charge mainly due to the oxygen vacancies. The relaxation observed for the M Double-Prime ({omega}) or Z Double-Prime ({omega}) curves is correlated to both localized and long range conduction. A single 'master curve' for the normalized plots of all the modulus isotherms observed for a given composition indicates that the conductivity relaxation is temperature independent.

  7. Structural, spectroscopic, and dielectric characterizations of Mn-doped 0.67BiFeO3-0.33BaTiO3 multiferroic ceramics

    KAUST Repository

    Hang, Qiming

    2013-09-07

    0.67BiFeO3-0.33BaTiO3 multiferroic ceramics doped with x mol% MnO2 (x = 2–10) were synthesized by solid-state reaction. The formation of a perovskite phase with rhombohedral symmetry was confirmed by X-ray diffraction (XRD). The average grain sizes were reduced from 0.80 μm to 0.50 μm as increasing the Mn-doped levels. Single crystalline nature of the grains was revealed by high-resolution transmission electron microscopy (HRTEM) images and electron diffraction patterns. Polar nano-sized ferroelectric domains with an average size of 9 nm randomly distributed in the ceramic samples were revealed by TEM images. Ferroelectric domain lamellae (71° ferroelectric domains) with an average width of 5 nm were also observed. Vibrational modes were examined by Raman spectra, where only four Raman peaks at 272 cm−1 (E-4 mode), 496 cm−1 (A 1-4 mode), 639 cm−1, and 1338 cm−1 were observed. The blue shifts in the E-4 and A 1-4 Raman mode frequencies were interpreted by a spring oscillator model. The dieletric constants of the present ceramics as a function of the Mn-doped levels exhibited a V-typed curve. They were in the range of 350–700 measured at 103 Hz, and the corresponding dielectric losses were in range of 0.43–0.96, approaching to 0.09 at 106 Hz.

  8. Chemical pressure induced change in multiferroicity of Bi1+2xGd2x/2Fe1-2xO3 bulk ceramics

    Science.gov (United States)

    Pradhan, S. K.; Sahu, D. R.; Rout, P. P.; Das, S. K.; Pradhan, A. K.; Srinivasu, V. V.; Roul, B. K.

    2017-04-01

    We have optimized Gd ion substitution in BiFeO3 (BFO) and observed prominently change in structural, electrical and magnetic behavior of Bi1+2xGd2x/2Fe1-2xO3 ceramics synthesized through slow step sintering schedule. It is observed that with the increase in concentration of Gd (x=0.1), original structure of BFO is transformed from rhombohedral R3c space group to orthorhombic Pn21a space group. Surprisingly, unit cell volume is drastically contracted (35% for x=0.2) and the sintered specimen showed enhanced room temperature ferromagnetic behavior although the original BFO is normally G-type antiferromagnetic in nature at 643 K. It is expected that intrinsic chemical pressure within the bulk body built by the substitution of Gd in presence of excess bismuth greatly supported through unidirectional movement of electrical dipole moment with in each individual domain as a result of which suppression of leakage current with enhanced dielectric and ferroelectric hysteresis is observed.

  9. Dielectric properties and relaxation of Bi0.5Na0.5TiO3–BaNb2O6 lead-free ceramics

    Indian Academy of Sciences (India)

    Chang-Rong Zhou; Xin-Yu Liu

    2007-12-01

    A new member of lead-free piezoelectric ceramics of the BNT-based group, (1 – )Bi0.5Na0.5TiO$_{3}–x$ BaNb2O6, was prepared by conventional solid state reaction and its dielectric properties and relaxation was investigated. X-ray diffraction showed that BaNb2O6 diffused into the lattice of Bi0.5Na0.5TiO3 to form a solid solution with perovskite-type structure. A diffuse character was proved by the linear fitting of the modified Curie–Weiss law. The temperature dependence of dielectric constant at different frequencies revealed that the solid solution exhibited relaxor characteristics different from classic relaxor ferroelectrics. The samples with = 0.002 and 0.006 exhibited obvious relaxor characteristics near the low temperature dielectric abnormal peak, f, and the samples with = 0.010 and 0.014 exhibited obvious relaxor characteristics between room temperature and f. The mechanism of relaxor behaviour was also discussed according to the macro-domain to micro-domain transition theory.

  10. Influence of the post-annealing cooling rate on the superconducting and mechanical properties of LFZ textured Bi-2212 rods

    CERN Document Server

    Natividad, E; Angurel, L A; Salazar, A; Pastor, J Y; Llorca, J

    2002-01-01

    Laser floating zone textured Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8 sub + subdelta (Bi-2212) thin rods were manufactured and subjected to a two-step annealing process at 870 deg C and 801 deg C in air. It was found that the subsequent cooling process led to marked changes in electrical properties. Three cooling rates were tested: (i) quenching in liquid nitrogen, (ii) cooling in air inside an alumina tube and (iii) cooling inside the furnace. The results showed that the faster the cooling rate, the higher the normal state resistivity. The T sub c distribution across the rods was also affected by the cooling rate, but no large differences were observed in the magnitude of the critical current at 77 K since the homogeneity of furnace-cooled samples compensated for the higher outer J sub c values of fast-cooled ones. The mechanical properties (elastic modulus and flexure strength) were not influenced by the cooling rate, but the samples quenched in liquid nitrogen were often cracked by thermal shock. The elastic m...

  11. Comparison of Structures and Dielectric Properties of Bi1.65Zn1.0Nb1.5O7.225 Ceramic and Thin Film%Bi1.65Zn1.0Nb1.5O7.225陶瓷和薄膜的结构和介电性能对比

    Institute of Scientific and Technical Information of China (English)

    张效华; 辛凤; 胡跃辉; 杨丰; 陈义川

    2012-01-01

    Based on the Bi1.5Zn1.0Nb1.5O7 formula, the non-stoichiometric pyrochlore Bi1.65 Zn1.0 Nb1.5 O7.225 (BZN) ceramic was prepared by adding the Bi2O3 with 10 mol% excess amount. Bi1.65 Zn1.0 Nb1.5 O7.225 ceramics were prepared by the conventional solid-state reaction technology. Thin films were prepared on Pt/ SiO2/Si(100) substrates by pulsed laser deposition. Bi1.65Zn1.0Nb1.5 O7.225 ceramic and thin film was compared to investigate the difference of crystallinity, microstructure and dielectric properties. The results indicated that the sintered BZN ceramic and the deposited BZN thin films have a pure cubic pyrochlore structure, however, BZN thin film exhibits the strong preferential orientation of (222) plane. The lattice constant and microstructure between ceramic and thin film also both exhibit the obvious difference. After contrast the dielectric properties of ceramic and thin film, it can be concluded that the dielectric constant of BZN thin film is significantly larger than that of BZN ceramic, which can be attributed to the difference between bulk ceramic and thin film, such as thickness, density and the preferential orientation, etc.%以立方焦绿石Bi1.5Zn1.0Nb1.5O7(BZN)为配方基础,通过掺入过量10%的Bi2O3,形成Bi1.65Zn1.0Nb1.5O7.225非化学计量比分子式.采用固相反应法合成具有焦绿石立方结构的Bi1.65Zn1.0Nb1.5O7.225陶瓷,并采用脉冲激光沉积法在Pt/SiO2/Si(100)基片上制备其薄膜.对比研究了非化学计量比Bi1.5Zn1.0Nb1.5O7.225陶瓷和薄膜的结晶性能,微观形貌以及介电性能的差异.结果表明烧结的Bi1.65Zn1.0Nb1.5O7.225陶瓷和沉积的BZN薄膜都保持立方焦绿石单相结构,但是薄膜展现出较强的(222)晶面择优取向.陶瓷和薄膜的晶格常数,微观形貌都体现出差异.对比二者的介电特性后发现,Bi1.65Zn1.0Nb1.5O7.225薄膜的介电常数明显高于陶瓷的介电常数,这归因于薄膜和块体材料之间的差异,例如厚度,致密度,择优取向等.

  12. Low-Temperature Sintering and Microwave Dielectric Properties of Bi0.9Ln0.05Li0.05V0.9Mo0.1O4 (Ln = Sm, Nd and La) Ceramics

    Science.gov (United States)

    Wang, Zixing; Yuan, Changlai; Yang, Tao; Feng, Qin; Liu, Fei; Chen, Jinman; Zhou, Changrong; Chen, Guohua

    2016-08-01

    Microwave dielectric ceramics of Bi0.9Ln0.05Li0.05V0.9Mo0.1O4 (Ln = Sm, Nd and La) with a low firing temperature were prepared via conventional solid-state reaction. The phases and microstructures of the ceramics were characterized by x-ray diffraction and scanning electron microscopy. The temperature coefficients of resonant frequency in the three compositions increased as sintering temperature increased. It is worth noting that a phase transition of the Bi0.9Ln0.05Li0.05V0.9Mo0.1O4 (Ln = Sm, Nd and La) ceramics from a monoclinic to a tetragonal scheelite structure was found with an increase in sintering temperature. The densification temperatures of all compositions were below 700°C. Excellent microwave dielectric properties were obtained for the Bi0.9Nd0.05Li0.05V0.9Mo0.1O4 ceramic sintered at 650°C, with a dielectric constant of ~72.2, a quality factor of ~6467 GHz and a temperature coefficient of resonant frequency of ~2.6 ppm/°C. The Bi0.9Ln0.05Li0.05V0.9Mo0.1O4 (Ln = Sm, Nd and La) ceramics are chemically compatible with both Ag and Cu powders at their sintering temperatures, and are thus a promising candidate for use in LTCC technology applications.

  13. Effect of MnO2 doping and temperature treatment on optical energy band gap properties in Zn-Bi-Ti-O varistor ceramics

    Science.gov (United States)

    Ghazali, M. S. M.; Abdullah, W. R. W.; Zakaria, A.; Kamari, H. M.; Rizwan, Z.

    2016-11-01

    In this study, the optical band-gap energy (Eg) was investigated with respect to MnO2 and sintering temperatures on ZnO based varistor ceramics. Eg of the ceramic (99-x) mol% ZnO + 0.5 mol% Bi2O3 + 0.5 mol% TiO2 + × MnO2 where × = 0, 0.2, 0.4, 0.6 and 0.8 mol%, were determined using UV-Vis spectrophotometer. The samples was prepared through solid-state route and sintered at the sintering temperature from 1110, 1140 and 1170 °C for 45 and 90 min in open air. At no doping of MnO2, the values of Eg are 2.991 ± 0.001, 2.989 ± 0.001 eV for 45 and 90 min sintering time; respectively. Eg was decreased to 2.192 ± 0.001 eV at 1140 °C at 45 min sintering time. Similar result of Eg was observed at longer heat treatment. Further addition of dopant causing the Eg decreases rapidly to 2.099 and 2.106 ± 0.001 eV at 45 and 90 min sintering time; respectively. XRD analysis indicates that there is hexagonal ZnO and secondary phases, Zn2MnO4, Bi4Ti3O12 and Zn2Ti3O8. The relative density of the sintered ceramics decreased or remain constant with the increase of MnO2 concentration for 45 min sintering time, however, further prolong sintering time; the relative density decreases form 90.25 to 88.35%. This indicates the pores are increasing with the increase of heat treatment. The variation of sintering temperatures to the optical band gap energy of based ZnO varistor doped with MnO2 due to the formation of interface states.

  14. Effect of HIPing on conductivity and impedance measurements of DyBi5Fe2Ti3O18 ceramics

    Indian Academy of Sciences (India)

    N V Prasad; G Prasad; Mahendra Kumar; S V Suryanarayana; T Bhimasankaram; G S Kumar

    2000-12-01

    X-ray diffraction, a.c. impedance and conductivity (a.c. and d.c.) have been used to characterize DyBi5Fe2Ti3O18. Samples were prepared by solid state double sintering method. A few samples were also subjected to hot isostatic pressing (HIP) at 800°C for 2 h at 100 MPa pressure. The data on XRD, impedance and conductivity of two sets of samples are compared to understand study of effect of HIPing on the properties of DyBi5Fe2Ti3O18.

  15. Influence of Cr2O3 additive and sintering temperature on the structural characteristics and piezoelectric properties of Bi4Ti2.95W0.05O12.05 Aurivillius ceramics

    Directory of Open Access Journals (Sweden)

    Yu Chen

    2016-12-01

    Full Text Available In this paper, Cr2O3 (0–0.4 wt% as an additive was added into Bi4Ti2.95W0.05O12.05 (BITW for preparing a kind of W/Cr co-doped BIT (BITW-yCr Aurivillius ceramics, both W6+ and Cr3+ are considered to substitute Ti4+ in the [TiO6] octahedron of BIT. Besides the orthorhombic Bi4Ti3O12 as the major phase, BITW-yCr ceramics also contain the cubic Bi2Ti2O7 as the second phase which was formed due to the doping effect of WO3, but its formation could be depressed by the addition of less Cr2O3. Additionally, the cell parameters of BITW ceramics are also changed by the incorporation of Cr2O3, as the distortion degree of the orthorhombic structure (a/b increases firstly and then decreases with its addtional amount (y. On the other hand, the grain growth of BITW-yCr ceramics is mainly controlled by the sintering process, there a higher sintering temperature results in a larger grain size. In comparison to BIT ceramics, BITW-yCr ceramics with less Cr-addition (y=0–0.2 require a higher sintering temperature to attain the best dense state, moreover, as y increases, the sintering temperature to gain the highest piezoelectric activity also increases. Finally, BITW-0.2Cr which was sintered at 1150 °C exhibits a higher piezoelectric activity than the others, which could be attributed to its larger orthorhombic distortion and larger grain size, its ideal piezoelectric constant (d33=28 pC/N provides it with great applying potentiality.

  16. Detailed magnetization study of superconducting properties of YBa{sub 2}Cu{sub 3}O{sub 7-x} ceramic spheres

    Energy Technology Data Exchange (ETDEWEB)

    Landau, I L; Willems, J B; Hulliger, J [Department of Chemistry and Biochemistry, University of Berne, Freiestrasse 3, CH-3012 Berne (Switzerland)], E-mail: landau@iac.unibe.ch

    2008-03-05

    We present a magnetization study of low density YBa{sub 2}Cu{sub 3}O{sub 7-x} ceramics carried out in magnetic fields H such that 0.5 Oesuperconducting links between grains may be completely suppressed either by a magnetic field H{approx}100 Oe (at low temperatures) or by an increase of temperature to above 70 K. This property of the present samples allowed us to evaluate the ratio between the average grain size and the magnetic field penetration depth {lambda}. Furthermore, at temperatures T>85 K, using low field magnetization measurements, we were able to evaluate the temperature dependence of {lambda}, which turned out to be very close to predictions from conventional Ginzburg-Landau theory. Although the present samples consisted of randomly oriented grains, specifics of magnetization measurements allowed for evaluation of {lambda}{sub ab}(T). Good agreement between our estimation of the grain size and the real sample structure provides evidence for the validity of this analysis of magnetization data. Measurements of the equilibrium magnetization in high magnetic fields were used for evaluation of H{sub c2}(T). At temperatures close to T{sub c}, the H{sub c2}(T) dependence turned out to be linear, in agreement with Ginzburg-Landau theory. The value of the temperature at which H{sub c2} vanishes coincides with the superconducting critical temperature evaluated from low field measurements, which is important evidence of the validity of both approaches to the analysis of magnetization data.

  17. Good Thermal Stability, High Permittivity, Low Dielectric Loss and Chemical Compatibility with Silver Electrodes of Low-Fired BaTiO3-Bi(Cu0.75W0.25)O3 Ceramics

    Science.gov (United States)

    Chen, Xiuli; Ma, Dandan; Chen, Jie; Huang, Guisheng; Zhou, Huanfu

    2016-09-01

    (1 - x)BaTiO3-xBi(Cu0.75W0.25)O3 [(1 - x)BT-xBCW, 0 ≤ x ≤ 0.04] perovskite solid solutions ceramics of an X8R-type multilayer ceramic capacitor with a low sintering temperature (900°C) were synthesized by a conventional solid state reaction technique. Raman spectra and x-ray diffraction analysis demonstrated that a systematically structural evolution from a tetragonal phase to a pseudo-cubic phase appeared near 0.03 co-fired multilayer capacitor applications.

  18. Separation of BSA through FAU-Type Zeolite Ceramic-Composite Membrane Formed on Tubular Ceramic Support: Optimization of Process Parameters by Hybrid Response Surface Methodology and Bi-Objective Genetic Algorithm.

    Science.gov (United States)

    Kumar, R Vinoth; Moorthy, I Ganesh; Pugazhenthi, G

    2017-03-09

    In this study, Faujasite (FAU) zeolite was coated on low cost tubular ceramic support as a separating layer via hydrothermal route. The mixture of silicate and aluminate solutions was used to create a zeolitic separation layer on the support. The prepared zeolite ceramic-composite membrane was characterized by using X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), particle size distribution (PSD), Field emission scanning electron microscopy (FESEM) and zeta potential measurements. The porosity of ceramic support (53%) was reduced by the deposition of FAU (43%) zeolite layer. The pore size and water permeability of the membrane were evaluated as 0.179 µm and 1.62 × 10(-7) m(3)/m(2)s.kPa, respectively, which are lower than that of the support (pore size of 0.309 µm and water permeability of 5.93 × 10(-7) m(3)/m(2)s.kPa). The permeate flux and rejection potential of the prepared membrane was evaluated by microfiltration of bovine serum albumin (BSA). To study the influences of three independent variables such as operating pressure (68.94 - 275.79 kPa), concentration of BSA (100 - 500 ppm) and solution pH (2 - 4) on permeate flux and percentage of rejection, the RSM (Response Surface Methodology) was employed. The predicted models for permeate flux and rejection were further subjected to bi-objective Genetic Algorithm (GA). The hybrid RSM-GA approach resulted a maximum permeate flux of 2.66 × 10(-5) m(3)/m(2)s and BSA rejection of 88.02%, at which the optimum conditions were attained as 100 ppm BSA concentration, 2 pH solution and 275.79 kPa applied pressure. In addition, the separation efficiency was compared with other membranes applied for BSA separation in order to know the potential of the fabricated FAU zeolite ceramic-composite membrane.

  19. Dielectric prop erties and high temp erature magnetic behavior on multiferroics Bi1-xCaxFeO3 ceramics%多铁材料Bi1-xCaxFeO3的介电、铁磁特性和高温磁相变∗

    Institute of Scientific and Technical Information of China (English)

    宋桂林; 苏健; 张娜; 常方高

    2015-01-01

    Multiferroic Bi1−xCaxFeO3 (x = 0, 0.05, 0.1, 0.15, 0.2) ceramics are prepared by sol-gel method. The effects of Ca doping on the structure, delectrical, ferromagnetism properties and high temperature magnetic behavior of BiFeO3 ceramics are studied. The structures of BiFeO3 ceramics are characterized by X-ray diffraction (XRD). The results show that all the peaks for Bi1−xFexO3 samples can be indexed according to the crystal structure of pure BiFeO3. The characteristic diffraction peaks of Bi1−xCaxFeO3 samples become gradually wider and the (104) and (110) peaks of BiFeO3 merge partially into a broadened peak (110) with Ca2+ doping increasing. XRD analysis reveals a phase transition in Ca-doped BiFeO3 from rhombohedral to orthorhombic when x is larger than 0.15. The scan electron microscope images indicate that Ca2+ doping significantly increases the grain sizes of BiFeO3 ceramic. The average grain sizes of Bi1−xCaxFeO3 samples range from 0.5 to 2 µm. The dielectric behaviors of Bi1−xCaxFeO3 ceramics change with content x and frequency. The dielectric constant measured at 1 kHz reaches a maximum value of εr =4603.9 when x=0.1, seven times as big as that of pure BiFeO3. With further increasing the Ca content (x=0.15, 0.2), the value of the dielectric constant is back to the level of pure BiFeO3. The dielectric constant of Bi0.8Ca0.2FeO3 (εr = 57) is less than one-tenth that of BiFeO3 (εr = 629.9). The dielectric losses of Bi1−xCaxFeO3 samples become smaller than that of BiFeO3 ceramic. This dramatic change in the dielectric properties of Bi1−xCaxFeO3 samples can be understood in terms of orientational relaxation of dipoles and the space charge limited conduction associated with crystal defects at low frequency. The magnetic measurements show that all samples possess strong ferromagnetism at room temperature expect BiFeO3 which is weakly ferromagnetic. The X-ray photoelectron spectroscopy spectrum indicates the coexistence of Fe2+and Fe3+ in Bi1

  20. Transport Barkhausen-like noise in uniaxially pressed Bi{sub 1.65}Pb{sub 0.35}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+{delta}}ceramic samples

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Fornaris, I. [Departamento de Ciencias Basicas, Universidad de Granma, Apdo. 21, P.O. Box 85100, Bayamo (Cuba); Govea-Alcaide, E. [Departamento de Fisica, Universidad de Oriente, Patricio Lumumba s/n, P.O. Box 90500, Santiago de Cuba (Cuba); Instituto de Fisica, Universidade de Sao Paulo, CP 66318, 05315-970 Sao Paulo, SP (Brazil); Alberteris-Campos, M. [Departamento de Engenharia Mecanica, Escola Politecnica, Universidade de Sao Paulo, 05508-900 Sao Paulo, SP (Brazil); Mune, P. [Departamento de Fisica, Universidad de Oriente, Patricio Lumumba s/n, P.O. Box 90500, Santiago de Cuba (Cuba); Jardim, R.F., E-mail: rjardim@if.usp.b [Instituto de Fisica, Universidade de Sao Paulo, CP 66318, 05315-970 Sao Paulo, SP (Brazil)

    2010-08-01

    We report on the detection of the transport Barkhausen-like noise (TBN) in polycrystalline samples of Bi{sub 1.65}Pb{sub 0.35}Sr{sub 2}Ca{sub 2} Cu{sub 3}O{sub 10+{delta}}(Bi-2223) which were subjected to different uniaxial compacting pressures. The transport Barkhausen-like noise was measured when the sample was subjected to an ac triangular-shape magnetic field (f {approx} 1 Hz) with maximum amplitude B{sub max} {approx} 5.5 mT, in order to avoid the flux penetration within the superconducting grains. Analysis of the TBN signal, measured for several values of excitation current density, indicated that the applied magnetic field in which the noise signal first appears, B{sub a}(t{sub i}), is closely related to the magnetic-flux pinning capability of the material. The combined results are consistent with the existence of three different superconducting levels within the samples: (i) the superconducting grains; (ii) the superconducting clusters; and (iii) the weak-links. We finally argue that TBN measurements constitute a powerful tool for probing features of the intergranular transport properties in polycrystalline samples of high-T{sub c} superconductors.

  1. Electronic and magnetic properties of superconducting LnO1-x F x BiS2 (Ln  =  La, Ce, Pr, and Nd) from first principles

    Science.gov (United States)

    Morice, Corentin; Artacho, Emilio; Dutton, Siân E.; Kim, Hyeong-Jin; Saxena, Siddharth S.

    2016-09-01

    A density functional theory study of the BiS2 superconductors containing rare-earths: LnO1-x F x BiS2 (Ln  =  La, Ce, Pr, and Nd) is presented. We find that CeO0.5F0.5BiS2 has competing ferromagnetic and weak antiferromagnetic tendencies, the first one corresponding to experimental results. We show that PrO0.5F0.5BiS2 has a strong tendency for magnetic order, which can be ferromagnetic or antiferromagnetic depending on subtle differences in 4f orbital occupations. We demonstrate that NdO0.5F0.5BiS2 has a stable magnetic ground state with weak tendency to order. Finally, we show that the change of rare earth does not affect the Fermi surface, and predict that CeOBiS2 should display a pressure induced phase transition to a metallic, if not superconducting, phase under pressure.

  2. Ferroelectric, piezoelectric, and dielectric properties of BiScO3-PbTiO3-Pb(Cd1/3Nb2/3)O3 ternary high temperature piezoelectric ceramics

    Science.gov (United States)

    Zhao, Tian-Long; Chen, Jianguo; Wang, Chun-Ming; Yu, Yang; Dong, Shuxiang

    2013-07-01

    (0.95-x)BiScO3-xPbTiO3-0.05Pb(Cd1/3Nb2/3)O3 (BS-xPT-PCN) high temperature piezoelectric ceramics near the morphotropic phase boundary (MPB) have been synthesized by traditional solid-state reaction methods. The microstructural morphology, phase structure, and electrical properties of BS-xPT-PCN ceramics were investigated in detail. X-ray diffraction analysis indicated BS-xPT-PCN ceramics have a pure perovskite structure. The coexistence of rhombohedral and tetragonal phases at MPB composition enhanced the polarizability by the coupling between two dynamically equivalent energy states, resulting in the improved piezoelectric and ferroelectric properties at MPB vicinity. The BS-xPT-PCN (x = 0.60) ceramics possess the optimal piezoelectric and ferroelectric properties with d33 = 505pC/N, kp = 55.9%, kt = 36.5%, strain = 0.23% (under the electric field 37.5 kV/cm), and Pr = 39.7 μC/cm2. High temperature dielectric behaviors showed diffuse phase transition in BS-xPT-PCN ceramics. The Curie temperature Tc was found to increase from 371 °C to 414 °C with x increasing from 0.58 to 0.62. All these results together with the good thermal stabilities make the BS-xPT-PCN ceramics promising candidates for high temperature piezoelectric applications.

  3. Electrical potential distribution in terahertz-emitting rectangular mesa devices of high- T c superconducting Bi2Sr2CaCu2O{}_{8+\\delta }

    Science.gov (United States)

    Watanabe, Chiharu; Minami, Hidetoshi; Kitamura, Takeo; Saiwai, Yoshihiko; Shibano, Yuki; Katsuragawa, Takuya; Kubo, Hiroyuki; Sakamoto, Kazuki; Kashiwagi, Takanari; Klemm, Richard A.; Kadowaki, Kazuo

    2016-06-01

    Excessive Joule heating of conventional rectangular mesa devices of the high-transition-temperature {T}{{c}} superconductor Bi2Sr2CaCu2O{}8+δ leads to hot spots, in which the local temperature T({\\boldsymbol{r}})\\gt {T}{{c}}. Similar devices without hot spots are known to obey the ac-Josephson relation, emitting sub-terahertz (THz) waves at frequencies f\\propto V/N, where V is the applied dc voltage or electrostatic potential and N is the number of active junctions in the device. However, it often has been difficult to predict the emission f from the applied V for two reasons: N is generally unknown and therefore has been assumed to be a fitting parameter, and especially when hot spots are present, V could develop a spatial dependence that cannot be accurately determined using two-terminal measurements. To clarify the situation, simultaneous SiC microcrystalline photoluminescence measurements of T({\\boldsymbol{r}}), Fourier-transform infrared (FTIR) measurements of f, and both two and four-terminal measurements of the local V({\\boldsymbol{r}}) were performed. The present four-probe measurements provide strong evidence that when a constant V is measured within the device's superconducting region outside of the hot spot, the only requirement for the accuracy of the ac-Josephson relation is the ubiquitous adjustment of the fitting parameter N. The four-probe measurements demonstrate that the electric potential distribution is strongly non-uniform near to the hot spot, but is essentially uniform sufficiently far from it. As expected, the emission frequency follows the ac-Josephson relation correctly even for low bath temperatures at which the system jumps to inner IV characteristic branches with smaller N values, reconfirming the ac-Josephson effect as the primary mechanism for the sub-THz emission.

  4. Diffuse phase transition and high-temperature dielectric relaxation study on (Bi{sub 0.5}Na{sub 0.5}){sub 1-x}Ba{sub x}TiO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Feng; Liu, Qiu-Xiang, E-mail: liuqx@gdut.edu.cn; Tang, Xin-Gui; Jiang, Yan-Ping; Yue, Jing-Long; Li, Jin-Kai

    2016-09-01

    Lead free (Bi{sub 0.5}Na{sub 0.5}){sub 1−x}Ba{sub x}TiO{sub 3} (x=0.6, 0.7, 0.8, 0.9) ferroelectric ceramics were synthesized by the traditional solid state reaction method. Sintering was carried out at 1200 °C for 2 h in air atmosphere. The structural, microstructure and Ferroelectric of ceramics were investigated. In dielectric studies, a diffuse phase transition was exhibited and a dielectric relaxation behavious was observed at high temperature range. Impedance analysis characterized grain and grain boundaries resistivities of the ceramics and calculated activation energy and the activation energy for conduction. Polaron theory indicates that the relaxation of the samples at high temperatures was associated with the hopping ions caused by oxygen vacancies.

  5. Struchre and Electrical Properties of (Na0.5Bi0.5)0.94Ba0.06TiO3 Ceramic with 0.5 wt% of MnO

    Institute of Scientific and Technical Information of China (English)

    LIU Weihua; XU Qing; CHEN Wen; CHEN Min; KIM Bokhee

    2008-01-01

    The structure and electrical properties of(Na0.5Bi0.5)0.94Ba0.06TiO3 ceramic doped with 0.5 wt% of MnO were investigated in comparison with those of(Na0.5Bi0.5)0.94Ba0.06TiO3 ceramic.It was ascertained that the MnO addition did not cause remarkable change in crystal structure and microstructure.The MnO addition mainly displayed a hard effect on the electrical properties,an increase of coercive field(Ec)and mechanical quality factor(Qm)together with a decrease of dielectric constant(?r)and piezoelectric constant(d33).An enhancement of electromechanical coupling factor(kp)with the MnO addition was obtained too.An essential relation between the piezoelectric properties and ferroelectric nature of the ceramics was detected.It was found that the piezoelectric properties of the ceramics highly depended on the corporative contribution of remanent polarization(Pr)and coercive field.

  6. Crystal Structure, Piezoelectric and Dielectric Properties of (Li, Ce)4+, Nb5+ and Mn2+ Co-doped CaBi4Ti4O15 High-Temperature Ceramics

    Science.gov (United States)

    Xin, Deqiong; Chen, Qiang; Wu, Jiagang; Bao, Shaoming; Zhang, Wen; Xiao, Dingquan; Zhu, Jianguo

    2016-07-01

    Bismuth-layered structured ceramics Ca0.85(Li,Ce)0.075Bi4Ti4- x Nb x O15-0.01MnCO3 were prepared by the conventional solid-state reaction method. The evolution of microstructure and corresponding electrical properties were studied. All the samples presented a single bismuth layered-structural phase with m = 4, indicating that (Li, Ce)4+, Nb5+ and Mn2+ adequately enter into the pseudo-perovskite structure and form solid solutions. It was found that Ca0.85(Li,Ce)0.075Bi4Ti3.98Nb0.02O15-0.01MnCO3 (CBTLCM-0.02Nb) ceramics possess the optimum electrical properties. The piezoelectric coefficient d 33, dielectric constant ɛ r, loss tan δ, planar electromechanical coupling factor k p and Curie-temperature T C of CBTLCM-0.02Nb ceramics were found to be ˜19.6 pC/N, 160, 0.16%, 8.1% and 767°C, respectively. Furthermore, the thermal depoling behavior demonstrates that the d 33 value of x = 0.02 content remains at 16.8 pC/N after annealing at 500°C. These results suggest that the (Li, Ce)4+-, Nb5+- and Mn2+-doped CBT-based ceramics are promising candidates for high-temperature piezoelectric applications.

  7. The doping effects of BiFe1-xCoxO3 (x =0.0-0.8)in layered perovskite Bi4Ti3O12 ceramics

    Institute of Scientific and Technical Information of China (English)

    Yang Wen-Lu; Chen Chun-Yan; Mao Xiang-Yu; Chen Xiao-Bing

    2012-01-01

    Bi5Fe1-xCoxTi3O15 (x =0.0,0.2,0.4,0.5,0.6,and 0.8) multiferroic ceramics are synthesized in two steps using the solid state reaction technique.X-ray diffraction patterns show that the samples have four-layer Aurivillius phases.At room temperature (RT),the samples each present a remarkable coexistence of ferromagnetism (FM) and ferroelectricity (FE).The remnant polarization (2Pr) reaches its greatest value of 14 μC/cm2 at x =0.6.Remnant magnetization (2Mr) first increases and then decreases,and the greatest 2Mr is 7.8 menu/g when x =0.5.The magnetic properties for x =0.4 are similar to those for x =0.6,indicating that the magnetic properties originate mainly from the coupling between Fe3+ and Co3+ ions,rather than from their own magnetic moments.

  8. Investigation of response of high-temperature superconducting Bi sub 2 Sr sub 2 CaCu sub 2 O sub y bolometer at hard substrate on infrared laser pulses of permanent power and variable relative pulse duration

    CERN Document Server

    Antonenko, S V; Korotkov, D P; Maltsev, S N

    2001-01-01

    A method for studying bolometric response of superconducting films to effect of a sequence of IR pulses of identical power and variable relative pulse duration using an optical rod was developed. A semiconductor laser was used as radiation source. Using the method suggested experiments on studying characteristics of a superconducting bolometer on the basis of Bi sub 2 Sr sub 2 CaCu sub 2 O sub y film on a MgO substrate were conducted. It was found that increase in pulse repetition frequency of IR laser in the range of 1-7 kHz brought about a decrease (by a factor of 2.5) of variable component of the bolometer response amplitude

  9. Structural characteristics of the new high-T/sub c/ superconducting phase Bi/sub 2/ Sr/sub 2/ Ca Cu/sub 2/ O/sub 8+x/

    Energy Technology Data Exchange (ETDEWEB)

    Carrillo, E.; Orozco, E.; Fuentes-Maya, J.; Mendoza, A.; Gasga, J.R.; Martinez, L.; Perez, R.; Garcia, A.; Schabes, P.S.; Acosta, D.

    1988-01-01

    A structural characterization of the superconducting phases in Bi/sub 2/ Sr/sub 2/ Ca Cu/sub 2/ O/sub 8+x/ is carried out. X-ray measurements are in agreement with recently reported diffraction patterns indicating an orthorhombic structure with large c-axis parameter (/approx/ 30A). Twin boundaries which are commonly found in high-T/sub c/ superconducting compounds based on Y or rare earths are however not frequent in these new type of superconductors. Transmission Electron Microscope images show a layered type of structure and electron diffraction patterns which confirm the orthorhombic structure. The resistivity measurements show a large drop at 100/sup 0/K with a T/sub c/ of the order of 76/sup 0/K.

  10. Effect of synthetic methods on the thermo electrical properties of textured Bi{sub 2}Ca{sub 2}Co{sub 1}.7O{sub x} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Rasekh, SH.; Madre, M. A.; Sotelo, A.; Guilmeau, E.; Marinel, S.; Diez, J. C.

    2010-07-01

    Thermoelectric performances on cobaltite ceramics can be changed by grain orientation. This can be performed by directional solidification on samples prepared from different synthetic methods. Three synthetic methods, conventional solid state reaction, sol-gel and polymer solution were used for preparation of Bi{sub 2}Ca{sub 2}Co{sub 1}.7O{sub x} powders. The powders have been directionally grown, at a rate of 30 mm/h, by the laser floating zone method. In all the cases, the microstructure shows alternated layers, of Bi{sub 2}Ca{sub 2}Co{sub 2}O{sub x} and a Bi-Ca-O solid solution, with small CoO inclusions. It has been found an improvement on the power factor at 50 degree centigrade for the solution methods with respect to the conventional solid sate sintered samples. (Author)

  11. Depolarization temperature and piezoelectric properties of Na1/2Bi1/2TiO3–Na1/2Bi1/2(Zn1/3Nb2/3)O3 ceramics by two-stage calcination method

    Indian Academy of Sciences (India)

    Xin-Yu Liu; Chang-Rong Zhou; Zhao-Hui Shan

    2007-12-01

    A new group of NBT-based lead-free piezoelectric ceramics, Na1/2Bi1/2TiO3–Na1/2Bi1/2(Zn1/3Nb2/3)O3, was synthesized using the two-stage calcination method and depolarization temperatures and piezoelectric properties were also investigated. The XRD analysis showed that the ceramics system had a morphotropic phase boundary (MPB) between the rhombohedral and the tetragonal structure. The highest piezoelectric properties of 33 = 97 pC/N and = 0.46 were obtained near MPB compositions. Furthermore, the depolarization temperatures near MPB compositions were slightly decreased and the lowest d was maintained at 210°C.

  12. Fabrication and Electrical Properties of Multilayer Ceramic Actuator Using Lead-Free (Bi1/2K1/2)TiO3

    Science.gov (United States)

    Nagata, Hajime; Tabuchi, Kazuya; Takenaka, Tadashi

    2013-09-01

    A prototype of a multilayer actuator (MLA) was fabricated using (Bi1/2K1/2)TiO3 (BKT) ceramics as active layers and Ag-Pd (7:3) as inner electrodes. Then, their microstructures and electrical properties were investigated. From the scanning electron microscope (SEM) observation, the thickness of the BKT active layers between electrodes was estimated to be approximately 60 µm for the body co-fired at 1045 °C for 10 h. Also, SEM images showed homogeneous and dense microstructures on the BKT active layers. Additionally, the interface between BKT and the Ag-Pd electrode was clearly distinguished and there are no significant signs of reaction or diffusion between them at least from the SEM micrographs. The resistivity ρ of BKT sample co-fired at 1045 °C for 10 h was about 1011 Ω.cm on average, which is sufficient for applying a high DC electric field to the sample. From the measurement of the field-induce strain S under unipolar driving at 100 kV/cm, a large strain of 0.14% at 100 kV/cm was obtained and the longitudinal dynamic displacement was 1 µm at the same electric field. The normalized d33* was calculated to be 138 pm/V, which is similar to that in the bulk samples. This result indicates that the BKT-based multilayered prototype efficiently functioned under unipolar driving up to 100 kV/cm.

  13. Effect of cooling rate on phase transitions and ferroelectric properties in 0.75BiFeO3-0.25BaTiO3 ceramics

    Science.gov (United States)

    Kim, Dae Su; Cheon, Chae Il; Lee, Seong Su; Kim, Jeong Seog

    2016-11-01

    The effect of the cooling rate on the electrical properties was investigated in the 0.75BiFeO3-0.25BaTiO3 ceramics. The air-quenched samples had superior ferroelectric and piezoelectric properties to the slowly cooled samples. The quenching effect weakened when the quenching temperature was less than 700 °C and eventually disappeared at 500 °C and below. The X-ray diffraction and transmission electron microscopy showed that the cooling rate had a significant effect on the crystal structure and domain structure. The slowly cooled sample showed a very small rhombohedral distortion and a poorly developed domain structure, which leads to weak ferroelectric and piezoelectric properties at room temperature. The quenched and slowly cooled samples had a ferroelectric rhombohedral structure (R3c) at room temperature and a paraelectric cubic structure (Pm-3m) at temperatures above 650 °C. On the other hand, the slowly cooled sample had a centro-symmetric orthorhombic (Pbnm) structure at intermediate temperatures, while the quenched sample had a noncentrosymmetric orthorhombic structure (Amm2). The diffusion of oxygen vacancies in the slowly cooled sample is believed to lead to a more symmetric orthorhombic structure at intermediate temperatures between 500 °C and 650 °C during the slow-cooling process and consequently very small rhombohedral distortion at room temperature.

  14. Anisotropic Ferro- and Dielectric Properties of Textured Bi4Ti3O12 Ceramics Prepared by the Solid-State Reaction Based on Multiple Calcination

    Directory of Open Access Journals (Sweden)

    Xiangyu Mao

    2010-01-01

    Full Text Available The grain-oriented Bi4Ti3O12 (BIT samples were prepared by the solid-state reaction method with a multicalcination process. The grain-oriented BIT samples exhibit anisotropic structural, ferroelectric, piezoelectric, and dielectric properties. The remanent polarization (2Pr and the piezoelectric constant (d33 of a/b- and c-direction BIT ceramics are 49.5 μC cm−2, 22.2 pC N−1 and 6.7 μC cm−2 6.9 pC N−1, respectively. The dielectric anomalies of samples are observed around 157 K and 232 K. The dielectric anomalies at around 157 K are related to oxygen vacancies. The activation energy of the dielectric relaxation of this anomaly is estimated to be 1.36 eV. Another dielectric anomaly at around 232 K is related to polarizable domains and the viscous motion of domain walls.

  15. Processing effects on the thermoelectric properties of Bi{sub 2}Ca{sub 2}Co{sub 1}.7O{sub x} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Rasekhi, S. H.; Constantinescu, G.; Madre, M. A.; Torres, M. A.; Diez, J. C.; Sotelo, A.

    2014-07-01

    Bi{sub 2}Ca{sub 2}Co{sub 1}.7O{sub x} bulk polycrystalline ceramics were prepared by the solid state method and by directional growth. Moreover, the effect of annealing on the textured materials has been studied. Microstructure has shown randomly oriented grains in the classical sintered materials while in the textured samples those were well oriented with their c-axis nearly perpendicular to the growth direction. Furthermore, the textured-annealed samples showed much lower amount of secondary phases than the as-grown ones. These microstructural changes are reflected on the thermoelectric properties which increase with the grain orientation and with the decrease on the secondary phase content mainly due to the electrical resistivity reduction. As a consequence, a raise on the power factor of about 6 and 9 times, compared with the classically sintered samples, was obtained for the as-grown and textured-annealed ones, respectively. The maximum power factor obtained at 650 degree centigrade in the textured-annealed samples (∼0.31 mW/K{sup 2}m) is about 50 % higher, at the same temperature, than the obtained in one of the most used methods for texturing this kind of materials, the sinter-forging process. (Author)

  16. A high temperature piezoelectric ceramic: (1-x)(Bi0.9La0.1)FeO(3-x)PbTiO3 crystalline solutions.

    Science.gov (United States)

    Chen, Jianguo; Qi, Yufa; Shi, Guiyang; Yu, Shengwen; Cheng, Jinrong

    2009-09-01

    (1-x)(Bi(0.9)La(0.1))FeO(3-x)PbTiO(3) (BLF-PT) crystalline solutions for x = 0.35, 0.37, 0.4, 0.43 and 0.45 have been prepared by the solid-state reaction method. The X-ray diffraction analysis shows that BLF-PT has a single perovskite phase with mixed tetragonal and rhombohedral phases between x = 0.4 and 0.43. The Curie temperature of BLF-PT for x = 0.4 attains 460 degrees C, which is about 80 degrees C higher than that of hard Pb(Zr,Ti)O(3) ceramics. The remnant polarization and piezoelectric constant of BLF-PT for x = 0.4 reach 38 microC/cm(2) and 112 pC/N, respectively. The planar coupling factor k(p) of BLF-PT for x = 0.4 remains stable at temperature increases of up to 360 degrees C. The impedance spectroscopy study reveals that the high temperature conduction of BLF-PT may be attributed to the motion of oxygen vacancies within the material. Our results indicate that BLF-PT is a promising candidate for high temperature applications.

  17. Influence of lanthanum distribution on dielectric and ferroelectric properties of BaBi{sub 4-x}La{sub x}Ti{sub 4}O{sub 15} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Khokhar, Anita [Department of Physics and Astrophysics, University of Delhi, Delhi 110 007 (India); Goyal, Parveen K., E-mail: goyalphy@gmail.com [Department of Physics, ARSD College, University of Delhi, Dhaula Kuan, New Delhi 110 021 (India); Thakur, O.P. [Electroceramics Group, Solid State Physics Laboratory, Lucknow Road, Delhi 110 054 (India); Shukla, A.K. [Department of Physics, Amity Institute of Applied Sciences, Amity University, Noida 201301 (India); Sreenivas, K., E-mail: kondepudysreenivas@gmail.com [Department of Physics and Astrophysics, University of Delhi, Delhi 110 007 (India)

    2015-02-15

    Structural and electrical properties of Lanthanum substituted barium bismuth titanate BaBi{sub 4-x}La{sub x}Ti{sub 4}O{sub 15} (0 ≤ x ≤ 0.50) ceramics prepared by conventional solid-state reaction method have been investigated. Raman spectra reveals the distribution of lanthanum into the perovskite layers and (Bi{sub 2}O{sub 2}){sup 2+} layers of BaBi{sub 4}Ti{sub 4}O{sub 15} ceramics. Room temperature dielectric constant (ε′) increases and considerable reduction in the low frequency (10{sup −2} to 10 Hz) dielectric losses and in dc conductivity (σ{sub dc}) are seen with lanthanum substitution. A critical La content of x ∼0.20 in BaBi{sub 4-x}La{sub x}Ti{sub 4}O{sub 15} exhibits a well-defined relaxor behavior as seen from the temperature and frequency dependence of the dielectric parameters ε′(T) and ε″(T). The dielectric data fit well to the modified Curie–Weiss law and the Lorentz-type relation and show increasing diffuseness in the phase transition with increasing La content. The temperature dependence of the characteristic relaxation time obtained from the Cole–Cole model shows a good fit to the non-linear Vogel–Fulcher relation. Improvements in the remnant polarization and a stable piezoelectric charge coefficient are seen up to a La content of x ∼0.20. The observed increase in dielectric loss and σ{sub dc} in addition to the diminished ferroelectric/piezoelectric properties for higher La content are explained in terms of changing oxygen vacancy concentration and structural relaxation due to the preferential incorporation of La into the (Bi{sub 2}O{sub 2}){sup 2+} layers as evidenced through the Raman spectroscopy. - Highlights: • La distribution in BaBi{sub 4-x}La{sub x}Ti{sub 4}O{sub 15} ceramics is analyzed through Raman spectroscopy. • Low and a nearly constant loss over wide frequency range (10{sup −2}–10{sup 7} Hz) obtained. • Critical La content x = 0.2 identified for high resistivity and ideal relaxor

  18. Piezoresponse Force Microscopy Imaging of Ferroelectric Domains in Bi(Zn1/2Ti1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 Piezoelectric Ceramics

    Institute of Scientific and Technical Information of China (English)

    LIU Li-Ming; ZENG Hua-Bong; CAO Zhen-Zhu; LENG Xue; ZHAO Kun-Yu; LI Guo-Rong; YIN Qing-Rui

    2011-01-01

    @@ Bismuth zinc titanate dopied lead magnesium niobate-lead titanate[Bi(Zn1/2Ti1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (BZT-PMN-PT)]piezoelectric ceramics are synthesized by the conventional solid state reaction method.Ferroelectric domain structures and the evolutionary behavior of BZT-PMN-PT ceramics under an external in-plane electric field are investigated by piezoresponse force microscopy(PFM).It is found that the BZT doping has a significant effect on the domain configurations and the domain kinetic behavior of the piezoelectric BZT-PMN-PT solid solution ceramics.Microdomains embedded in the macrodomains, induced by the BZT dopant in the solid solution ceramics, are clearly observed by PFM and their volume increases with increasing amounts of BZT doping.The microdomains of BZT-PMN-PT piezoelectric ceramics exhibit better domain dynamic behavior stability than macrodomains under an external in-plane electric held.

  19. Improved ferroelectric/piezoelectric properties and bright green/UC red emission in (Li,Ho)-doped CaBi4Ti4O15 multifunctional ceramics with excellent temperature stability and superior water-resistance performance.

    Science.gov (United States)

    Xiao, Ping; Guo, Yongquan; Tian, Mijie; Zheng, Qiaoji; Jiang, Na; Wu, Xiaochun; Xia, Zhiguo; Lin, Dunmin

    2015-10-21

    Multifunctional materials based on rare earth ion doped ferro/piezoelectrics have attracted considerable attention in recent years. In this work, new lead-free multifunctional ceramics of Ca1-x(LiHo)x/2Bi4Ti4O15 were prepared by a conventional solid-state reaction method. The great multi-improvement in ferroelectricity/piezoelectricity, down/up-conversion luminescence and temperature stability of the multifunctional properties is induced by the partial substitution of (Li0.5Ho0.5)(2+) for Ca(2+) ions in CaBi4Ti4O15. All the ceramics possess a bismuth-layer structure, and the crystal structure of the ceramics is changed from a four layered bismuth-layer structure to a three-layered structure with the level of (Li0.5Ho0.5)(2+) increasing. The ceramic with x = 0.1 exhibits simultaneously, high resistivity (R = 4.51 × 10(11)Ω cm), good piezoelectricity (d33 = 10.2 pC N(-1)), high Curie temperature (TC = 814 °C), strong ferroelectricity (Pr = 9.03 μC cm(-2)) and enhanced luminescence. These behaviours are greatly associated with the contribution of (Li0.5Ho0.5)(2+) in the ceramics. Under the excitation of 451 nm light, the ceramic with x = 0.1 exhibits a strong green emission peak centered at 545 nm, corresponding to the transition of the (5)S2→(5)I8 level in Ho(3+) ions, while a strong red up-conversion emission band located at 660 nm is observed under the near-infrared excitation of 980 nm at room temperature, arising from the transition of (5)F5→(5)I8 levels in Ho(3+) ions. Surprisingly, the excellent temperature stability of ferroelectricity/piezoelectricity/luminescence and superior water-resistance behaviors of piezoelectricity/luminescence are also obtained in the ceramic with x = 0.1. Our study suggests that the present ceramics may have potential applications in advanced multifunctional devices at high temperature.

  20. High-T{sub c} superconductivity in Bi{sub 1.6}Pb{sub 0.4}Sr{sub 2}Ca{sub 2}Cu{sub 2+x}O{sub y} compounds

    Energy Technology Data Exchange (ETDEWEB)

    Ali, Zahida; Maqsood, Asghari; Maqsood, Muhammad; Ramay, S.M.; Yousaf, Mohammad [Thermal Physics Laboratory, Department of Physics, Quaid-I-Azam University, Islamabad (Pakistan); Anwar-ul-Haq [Metallurgy Division, Dr A Q Khan Research Laboratories, Kahuta, Rawalpindi (Pakistan)

    1996-05-01

    Superconducting samples with the nominal composition Bi{sub 1.6}Pb{sub 0.4}Sr{sub 2}Ca{sub 2}Cu{sub 2+x}O{sub y} (x = 1.6, 1.8, 2.0) have been prepared by a solid state reaction technique. The resistivity data reveal the occurrence of multi phases in all the samples. By a process of ageing over 2 years then re annealing, a dramatic increase in T{sub c} was observed in the above system for x=2.0. We achieved zero resistance at 130 K, which is the highest in the composition Bi{sub 1.6}Pb{sub 0.4}Sr{sub 2}Ca{sub 2}Cu{sub 2+x}O{sub y} (x = 1.6, 1.8, 2.0) reported so far but the recipe is often not reproducible. This shows that the system is sensitive to Cu composition and to the conditions of preparation. Furthermore, long storage leads to a deterioration in the superconducting properties. X-ray diffraction studies show that these samples mainly contain the (2223) phase. However, in each sample, a few lines could not be indexed, which may indicate the presence of some new phase. (author)

  1. Effect of Pb substitution on the thermo electrical properties of textured Bi{sub 2}Ca{sub 2}Co{sub 1}.7O{sub y} ceramics prepared by a polymer solution method

    Energy Technology Data Exchange (ETDEWEB)

    Rasekh, S. H.; Madre, M. A.; Diez, J. C.; Guilmeau, E.; Marinel, S.; Sotelo, A.

    2010-07-01

    Thermo electrical properties of cobaltate ceramics can be tuned up by choosing the adequate synthetic method, cation substitution and subsequent grain orientation. This can be performed preparing the ceramics by a polymer solution method, using Pb partially substituting Bi, and texturing by directionally growing from the melt. In this work, Bi{sub 2}-xPb{sub x}Ca{sub 2}Co{sub 1}.7O{sub y} (x 0.0, 0.2, 0.4 and 0.6) ceramics, prepared by a polymer solution method, have been directionally grown, with the Laser Floating Zone (LFZ) technique, at 30 mm/h. In all the cases, the microstructure shows alternated layers with small CoO inclusions. It has been found a very important decrease on the resistivity and, at the same time, on the thermopower. However, the power factor values are improved with Pb addition, reaching power factor values, for samples with 0.4 Pb substitution, as high as two times the values obtained for undoped ones. (Author) 30 refs.

  2. Effects of V2O5 Additive on Structure and Dielectric Properties of BiNbO4 Ceramics

    Directory of Open Access Journals (Sweden)

    Lisińska-Czekaj A.

    2013-12-01

    Full Text Available Celem niniejszej pracy było zbadanie wpływu dodatku V2O5 na strukturę i właściwości dielektryczne ceramiki BiNbO*. Do wytworzenia ceramiki zastosowano metodę reakcji w fazie stałej i spiekanie swobodne w atmosferze powietrza. Cera- mikę poddano badaniom morfologii (SEM. składu chemicznego (EDS oraz rentgenowskiej analizie fazowej i strukturalnej. Właściwości dielektryczne w domenie częstotliwości (v =10Hz-lMHz i temperatury (T =RT-550°C zbadano przy pomocy spektroskopii impedancyjnej. Stwierdzono, że dodatek V2O5 powoduje niewielką zmianę parametrów komórki elementarnej, zmniejsza porowatość ceramiki oraz pozwolił zaobserwować zjawiska relaksacyjne występujące w dwóch zakresach częstotli- wości: v = 102-I03Hz oraz v =105-106Hz w temperaturze T>285°C.

  3. Oxygen vacancy-induced ferromagnetism in Bi4NdTi3FeO15 multiferroic ceramics

    Science.gov (United States)

    Zhang, Dalong; Feng, Lei; Huang, Weichuan; Zhao, Wenbo; Chen, Zhiwei; Li, Xiaoguang

    2016-10-01

    Layered Aurivillius compounds with multiferroic properties have attracted much attention due to their rich fundamental physics and great application potential. However, the ferroelectric and magnetic properties are different for these compounds with different synthesis conditions. In this paper, we investigate the structure, ferroelectricity, and magnetism of four-layer Aurivillius-phase multiferroic Bi4NdTi3FeO15. The four-layer structure is confirmed by powder X-ray diffraction and high-angle annular dark field scanning transmission electron microscopy. The ferroelectricity together with dielectric constant can be reduced by vacuum-annealing treatment due to the increase of oxygen vacancy concentration. More interestingly, the ferromagnetism is strongly enhanced by vacuum-annealing and can be obviously suppressed after re-oxidization, which may be associated with Fe3+-O-Fe2+ coupling originated from the variable valence state of Fe with different oxidization conditions. These findings indicate that oxygen vacancies play a crucial role in the ferroelectric and magnetic properties in Aurivillius compounds synthesized by different conditions.

  4. Free-standing oxide superconducting articles

    Science.gov (United States)

    Wu, Xin D.; Muenchausen, Ross E.

    1993-01-01

    A substrate-free, free-standing epitaxially oriented superconductive film including a layer of a template material and a layer of a ceramic superconducting material is provided together with a method of making such a substrate-free ceramic superconductive film by coating an etchable material with a template layer, coating the template layer with a layer of a ceramic superconductive material, coating the layer of ceramic superconductive material with a protective material, removing the etchable material by an appropriate means so that the etchable material is separated from a composite structure including the template lay This invention is the result of a contract with the Department of Energy (Contract No. W-7405-ENG-36).

  5. Dielectric properties of xNa0.5Bi0.5TiO3-(1 ‑ x)Ba0.66Mg0.04Sr0.3TiO3 composite ceramics

    Science.gov (United States)

    Wang, Jing; Cheng, Haiyan; Gao, Lan; Wang, Xianling; Duan, Ruijie; Li, Jiali

    2017-02-01

    The ceramics with the composition of xNa0.5Bi0.5TiO3-(1 ‑ x)Ba0.66Mg0.04Sr0.3TiO3 (NBT-BMST) in which x = 0.2, 0.3, 0.4 and 0.5 were prepared successfully by the solid-state reaction method. The effects of NBT-doping on phase structure, morphology, temperature stability and dielectric properties had been investigated in detail. The XRD results show that the composites are composed of tetragonal perovskite. The phase structure of NBT-BMST is observed by scanning electron microscopy. The dielectric constant of 0.3Na0.5Bi0.5TiO3-0.7Ba0.66Mg0.04Sr0.3TiO3 ceramic is ˜4100, the temperature coefficients of capacitance are ‑15%, 15% and 22% at ‑55∘C, 60∘C and 200∘C, respectively. And the dielectric loss is less than 0.13, which is obviously superior to other compositions. The results of this work showed that the component of 0.3Na0.5Bi0.5TiO3-0.7Ba0.66Mg0.04Sr0.3TiO3 is a promising candidate to high-temperature stable materials.

  6. Piezoelectric, impedance, electric modulus and AC conductivity studies on (Bi0.5Na0.50.95Ba0.05TiO3 ceramic

    Directory of Open Access Journals (Sweden)

    Ansu K. Roy

    2013-06-01

    Full Text Available Lead-free piezoelectric perovskite ceramic (Bi0.5Na0.50.95Ba0.05TiO3 (BNT-BT0.05, prepared by conventional high temperature solid state reaction technique at 1160 °C/3h in air atmosphere, is investigated by impedance and modulus spectroscopy in a temperature range 35–400 °C, over a frequency range 100 Hz–1 MHz. The crystal structure, microstructure, and piezoelectric properties as well as the AC conductivity of the sample were studied. Powder X-ray diffraction pattern derived from the resulting data at the room temperature subjected to Rietveld refinements and Williamson-Hall plot analysis confirmed the formation of phase pure compound with monoclinic unit cells having a crystallite-size ~33.8 nm. Observed SEM micrograph showed a uniform distribution of grains inside the sample having an average grain size ~3 mm. Longitudinal piezoelectric charge coefficient of the sample poled under a DC electric field of ~ 2.5 kV/mm at 80 °C in a silicone oil bath was found to be equal to 95 pC/N. The frequency and temperature dependent electrical data analysed in the framework of AC conductivity, complex impedance as well as electric modulus formalisms showed negative temperature coefficient of resistance (NTCR character of the material and the dielectric relaxation in the material to be of non-Debye type. Double power law for the frequency-dependence of AC conductivity and Jump Relaxation Model (JRM were found to explain successfully the mechanism of charge transport in BNT-BT0.05.

  7. 钇稳定氧化锆-饰面瓷结构双轴弯曲强度的研究%Study on bi-axial flexure strength of Upcera zirconia core/veneer ceramic composites

    Institute of Scientific and Technical Information of China (English)

    周珊羽; 王琳琳; 胡琛; 邵龙泉

    2012-01-01

    Objective To study the bi-axial flexure slrenglh of bilayered Upcera zirconia core and the veneering porcelain. Methods Forty disk specimens were made from different core and veneering porcelain, and divided inlo four groups as follows( n = 10) :Upcera core + Cercon ceram kiss veneer( group A) , Upcera core + IPS e. Max Ceram veneer( group B) , Cercon Brain Expert core + Cercon ceram kiss veneer( group C)and IPS e. Max CAD core + IPS e. Max Ceram veneer ( group D). The bi-axial flexure slrenglh were measured by ball-on-ring tesl. Results The value of bi-axial flexure slrenglh were ( 132. 03 ± 3. 05 ) Mpa for group A, ( 129. 91 ± 2. 06 ) Mpa for group B, ( 123. 97 ± 3. 04 ) Mpa for group C, ( 120. 96 ± 2. 09 ) Mpa for group D. There were significant differences among 4 groups( P < 0. 05 ). The bi-axial flexure slrenglh of group A and B were significantly higher than that of group C and D. The specimens displayed mainly crack propagalion ihrough ihe composite interface withoul delaminalion. Conclusions Veneering porcelain has no influence on bi-axial flexure slrenglh, failure mode of 4-group bi-layers slruclures is complete fraclure, there is a good bonding properly between Upcera zirconia core and the veneering porcelain.%目的 检测国产钇稳定氧化锆与饰面瓷双层结构的双轴弯曲强度,分析双层瓷结构的失败模式.方法 制作40个核瓷-饰面瓷的双层瓷结构试件,根据材料不同分为4组:A组:Upcera核瓷+Cercon ceram kiss饰面瓷;B组:Upcera核瓷+IPS e.max Ceram饰面瓷;C组:Cercon Brain Expert核瓷+Cercon ceram kiss饰面瓷;D组:IPS e.max CAD核瓷+IPS e.max Ceram饰面瓷(n=10).采用球-环法测定试件的双轴弯曲强度.结果 双轴弯曲强度分别为A组:(132.03±3.05)MPa;B组:(129.91±2.06)MPa;C组:(123.97±3.04)MPa;D组:(120.96±2.09)MPa.组间有统计学差异(P<0.05).A组和B组的双轴弯曲强度显著性高于C组和D组.失败模式主要为核瓷-饰面瓷的完全断裂.结论 饰面瓷对钇

  8. Ferroelectric, piezoelectric, and dielectric properties of BiScO{sub 3}-PbTiO{sub 3}-Pb(Cd{sub 1/3}Nb{sub 2/3})O{sub 3} ternary high temperature piezoelectric ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Tianlong [Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871 (China); School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Chen Jianguo; Dong Shuxiang [Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871 (China); Wang Chunming [School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Yu Yang [Faculty of Physics and Electronic Technology, Hubei University, Wuhan 430062 (China)

    2013-07-14

    (0.95-x)BiScO{sub 3}-xPbTiO{sub 3}-0.05Pb(Cd{sub 1/3}Nb{sub 2/3})O{sub 3} (BS-xPT-PCN) high temperature piezoelectric ceramics near the morphotropic phase boundary (MPB) have been synthesized by traditional solid-state reaction methods. The microstructural morphology, phase structure, and electrical properties of BS-xPT-PCN ceramics were investigated in detail. X-ray diffraction analysis indicated BS-xPT-PCN ceramics have a pure perovskite structure. The coexistence of rhombohedral and tetragonal phases at MPB composition enhanced the polarizability by the coupling between two dynamically equivalent energy states, resulting in the improved piezoelectric and ferroelectric properties at MPB vicinity. The BS-xPT-PCN (x = 0.60) ceramics possess the optimal piezoelectric and ferroelectric properties with d{sub 33} = 505pC/N, k{sub p} = 55.9%, k{sub t} = 36.5%, strain = 0.23% (under the electric field 37.5 kV/cm), and P{sub r} = 39.7 {mu}C/cm{sup 2}. High temperature dielectric behaviors showed diffuse phase transition in BS-xPT-PCN ceramics. The Curie temperature T{sub c} was found to increase from 371 Degree-Sign C to 414 Degree-Sign C with x increasing from 0.58 to 0.62. All these results together with the good thermal stabilities make the BS-xPT-PCN ceramics promising candidates for high temperature piezoelectric applications.

  9. Effect of doped Mn on piezoelectric properties of (Na0.5Bi0.5)0.92 Ba0.08TiO3 lead-free ceramics

    Institute of Scientific and Technical Information of China (English)

    ZHOU Xiao-yuan; GU Hao-shuang; LI Wei-yong

    2005-01-01

    Piezoelectric ceramics (Na0.5Bi0.5)0.92Ba0.08 TiO3 +x% MnCO3 (BNBT-Mn, x= 0 - 1. 6, mass fraction)were synthesized by conventional solid state reaction. The results show that when the addition of MnCO3 is 0 -1.4%, BNBT-Mn ceramics exhibit a single-phase perovskite structure. With the increase of content of MnCO3, piezoelectric constant and electromechanical coupling factor increase rapidly when x is lower than 0.3. Then they both decrease when x is in the range of 0.3 and 1.6. When x=0.3, piezoelectric constant and electromechanical coupling factor reach the maximum value of 160 pC/N and 58.5% respectively, which can improve the temperature stability of BNBT-Mn.

  10. Dielectric diffusive behavior of (Lax(Na0.5Bi0.5)1-1.5x)0.97Ba0.03TiO3 lead-free ceramics

    Science.gov (United States)

    Yu, Zi-de; Chen, Xiao-ming

    2016-12-01

    We investigate in the present work the additional data to the previous reported paper (Zhao, et al.) that sufficiently enrich to understand the dielectric diffusive behavior of the (Lax(Na0.5Bi0.5)1-1.5x)0.97Ba0.03TiO3 lead-free ceramics. The dielectric diffusive behavior of the ceramics was investigated using Lorentz-type quadratic relationship and Gaussian-type quadratic relationship. By calculating mean-square-root error and dielectric constant variance, it was found that Lorenz-type quadratic relationship was better to describe the characterization of dielectric diffusive behavior than Gaussian-type quadratic relationship. The results confirm that the increase in La3+ content causes an increase in the degree of diffuseness of dielectric peak.

  11. Dielectric and Raman studies of Ba0.06(Na1/2Bi1/20.94TiO3–NaNbO3 ceramics

    Directory of Open Access Journals (Sweden)

    Roy Sumit K.

    2016-06-01

    Full Text Available In this work the X-ray diffraction, scanning electron microscopy, Raman and dielectric studies of lead free perovskite (1 – xBa0.06(Na1/2Bi1/20.94TiO3–xNaNbO3 (0 ⩽ x ⩽ 1.0 ceramics, prepared using a standard solid state reaction method, were investigated. X-ray diffraction studies of all the ceramics suggested the formation of single phase with crystal structure transforming from rhombohedral-tetragonal to orthorhombic symmetry with the increase in NaNbO3 content. Raman spectra also confirmed the formation of solid solution without any new phase. Dielectric studies showed that the phase transition is of diffusive character and diffusivity parameter decreases with increasing NaNbO3 content. The compositional fluctuation was considered to be the main cause of diffusivity.

  12. Role of nickel ion coordination on spectroscopic properties of multi-component CaF2-Bi2O3-P2O5-B2O3 glass-ceramics

    Science.gov (United States)

    Suresh, S.; Narendrudu, T.; Kumar, A. Suneel; Rao, M. V. Sambasiva; Ram, G. Chinna; Rao, D. Krishna

    2016-10-01

    Multi-component CaF2-Bi2O3-P2O5-B2O3 glasses doped with different concentrations of NiO were crystallized through heat treatment. The prepared glass ceramic samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), differential thermal analysis (DTA) as well as conventional spectroscopic studies viz., optical absorption, Fourier transform infrared (FTIR) and Raman. The XRD and SEM studies have indicated that the samples contain well defined and randomly distributed grains of different crystalline phases. The optical absorption studies together with FTIR and Raman measurements indicated the gradual transformation of nickel ions from tetrahedral sites to octahedral sites (lasing sites) as the concentration of NiO is increased beyond 1.5 mol%. All these investigations have indicated that the growing degree of disorder in the glass ceramic network at higher concentrations of NiO. Glass ceramics doped with NiO beyond 1.5 mol% appear to be suitable for getting laser emission due to 3T2(F) → 3A2(F) transition in NIR region. These glass-ceramics can be expected as an amplification medium for tunable lasers and broadband optical amplifiers for wavelength division multiplexing transmission system.

  13. Dielectric properties of (Na0.5Bi0.5)TiO3-Ba0.7Sr0.3Sn0.02Ti0.98O3 composite ceramics

    Science.gov (United States)

    Wang, Jing; Rong, Guijuan; Liu, Lei; Cheng, Haiyan; Jiang, Qi; Li, Chuangchuang; Wang, Mengmeng

    2016-05-01

    Lead-free x(Na0.5Bi0.5)TiO3-(1 - x)Ba0.7Sr0.3Sn0.02Ti0.98O3 (NBT-BSST) ceramics are prepared by a wet solid-phase reaction method. The effect of NBT/BSST ratio on phase structure, microstructure and dielectric properties has been investigated in detail. The X-ray diffraction (XRD) analysis illustrates that the composites are composed of tetragonal perovskite. With increasing NBT content, the ceramic capacitors display stronger temperature stability in its dielectric behavior. A great enhance of dielectric properties and other electric parameters is obtained in this system by properly modulating the compositions. For example, the composite ceramics with 30% NBT content possess a large dielectric constant (𝜀r) of 3200 and a low dielectric loss (tan δ) of 0.09. The temperature coefficient of capacitance of NBT-BSST varies from -50% to 20% while the NBT content is 30% at the whole range of measured temperature. The results show that NBT-BSST ceramics are a good candidate of lead-free dielectric materials.

  14. Composition-dependent structural, dielectric and ferroelectric responses of lead-free Bi0.5Na0.5TiO3-SrZrO3 ceramics

    Science.gov (United States)

    Maqbool, Adnan; Hussain, Ali; Rahman, Jamil Ur; Malik, Rizwan Ahmed; Song, Tae Kwon; Kim, Myong-Ho; Kim, Won-Jeong

    2016-06-01

    The influence of SrZrO3 (SZ) addition on the crystal structure, piezoelectric and the dielectric properties of lead-free Bi0.5Na0.5TiO3 (BNT-SZ100 x, with x = 0 - 0.10) ceramics was systematically investigated. A significant reduction in the grain size was observed with SZ substitution. The X-ray diffraction analysis of the sintered BNT-SZ ceramics revealed a single perovskite phase with a pseudocubic symmetry; however, electric poling indicated a non-cubic distortion in the poled BNT-SZ ceramics. With increase in the SZ content, the temperature of maximum dielectric constant ( T m ) shifted towards lower temperatures, and the curves became more diffuse. Enhanced piezoelectric constant ( d 33 = 102 pC/N) and polarization response were observed for the BNT-SZ5 ceramics. The results indicated that SZ substitution induced a transition from a ferroelectric to relaxor state with a field-induced strain of 0.24% for BNT-SZ9 corresponding to a normalized strain of 340 pm/V.

  15. Good Thermal Stability, High Permittivity, Low Dielectric Loss and Chemical Compatibility with Silver Electrodes of Low-Fired BaTiO3-Bi(Cu0.75W0.25)O3 Ceramics

    Science.gov (United States)

    Chen, Xiuli; Ma, Dandan; Chen, Jie; Huang, Guisheng; Zhou, Huanfu

    2017-01-01

    (1 - x)BaTiO3- xBi(Cu0.75W0.25)O3 [(1 - x)BT- xBCW, 0 ≤ x ≤ 0.04] perovskite solid solutions ceramics of an X8R-type multilayer ceramic capacitor with a low sintering temperature (900°C) were synthesized by a conventional solid state reaction technique. Raman spectra and x-ray diffraction analysis demonstrated that a systematically structural evolution from a tetragonal phase to a pseudo-cubic phase appeared near 0.03 x X-ray photoelectron analysis confirmed the existence of Cu+/Cu2+ mixed-valent structure in 0.96BT-0.04BCW ceramics. 0.96BT-0.04BCW ceramics sintered at 900°C showed excellent temperature stability of permittivity (Δ ɛ/ ɛ 25°C ≤ ±15%) and retained good dielectric properties (relative permittivity ˜1450 and dielectric loss ≤2%) over a wide temperature range from 25°C to 150°C at 1 MHz. Especially, 0.96BT-0.04BCW dielectrics have good compatibility with silver powders. Dielectric properties and electrode compatibility suggest that the developed materials can be used in low temperature co-fired multilayer capacitor applications.

  16. Dielectric relaxation on Ba{sub 1-x}Bi{sub 2x/3}Zr{sub 0.25}Ti{sub 0.75}O{sub 3} ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Badapanda, T., E-mail: badapanda.tanmaya@gmail.com [Department of Physics, National Institute of Technology, Rourkela 769008 (India); Senthil, V. [Department of Physics, National Institute of Technology, Rourkela 769008 (India); Rout, S.K. [Department of Applied Physics, Birla Institute of Technology, Mesra, Ranchi (India); Panigrahi, S. [Department of Physics, National Institute of Technology, Rourkela 769008 (India); Sinha, T.P. [Department of Physics, Bose Institute, 93/1 A.P.C. Road, Kolkata 700009 (India)

    2012-04-16

    Highlights: Black-Right-Pointing-Pointer Perovskite-type cubic structure with space group Pm3m. Black-Right-Pointing-Pointer ac conductivity obeys the Jonscher's universal power law. Black-Right-Pointing-Pointer Space charge polarization is easy to activate thermally. Black-Right-Pointing-Pointer Ba{sub 1-x}Bi{sub 2x/3}Zr{sub 0.25}Ti{sub 0.75}O{sub 3} (x = 0.025) ceramic behaves like negative temperature coefficient of resistance (NTCR). - Abstract: Polycrystalline (Ba{sub 1-x}Bi{sub 2x/3}Zr{sub 0.25}Ti{sub 0.75}O{sub 3}) (x = 0.025) (BBZT) ceramic, is prepared by solid-state reaction. The X-ray diffraction of the sample at room temperature shows single-phase compound in a cubic crystal system. The electrical behavior (complex impedance Z*, complex permittivity {epsilon}*, complex modulus M*) of the BBZT ceramic has been studied by non-destructive complex impedance spectroscopy (CIS) as a function of frequency at different temperatures. Grain and grain boundary conduction is observed from complex impedance spectrum by the appearance of two semicircular arcs in the Nyquist plot. The presence of non-Debye type multiple relaxations has been confirmed by complex modulus analysis. The Nyquist plot shows the negative temperature coefficient of resistance (NTCR) character of BBZT. Variation of ac conductivity as a function of frequency shows that the compound exhibits Arrhenius-type of electrical conductivity. The ac conductivity data are used to evaluate the density of states at Fermi level and activation energy of this ceramic. The dc electrical and thermal conductivities of grain and grain boundary have been discussed.

  17. SOLID STATE SINTERING PREPARED 0.935(Bi0.5Na0.5TiO3-0.065BaTiO3 LEAD FREE CERAMICS: EFFECT OF POLING CONDITIONS

    Directory of Open Access Journals (Sweden)

    HAMZA LIDJICI

    2012-03-01

    Full Text Available In this work , the influence of poling conditions (poling field, poling temperature and poling time on the piezoelectric properties of 0.935(Bi0.5Na0.5 TiO3-0.065BaTiO3 (BNT6.5BT lead-free ceramics was examined. Piezoelectric properties like piezoelectric constant (d33 and electromechanical factors (Kp ,Kt depend on poling field and poling temperature, whereas different poling times, in the 5-30 min range, were not observed to have significant effect on the piezoelectric properties.

  18. Friction and wear behavior of the superconducting compound oxide of Ag/Bi_(1. 6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x)%超导Ag/Bi_(1.6)Pb_(0.4)Sr_2Ca_2Cu_3O_(10-x)复合氧化物摩擦磨损性能

    Institute of Scientific and Technical Information of China (English)

    彭义; 李长生; 董丽荣; 丁巧党; 王昊璐

    2009-01-01

    The superconducting Bi_(1.6)Pb_(0.4)Sr_2Ca_2Cu_3O_(10-x) samples were prepared by the solid-state synthesismethod. The tribological properties were measured on the friction and wear tester from ambient temperature toliquid nitrogen temperature. The results indicate that the friction coefficient of Bi_(1.6)Pb_(0.4)Srz_2Ca_2Cu_30_(10-x) againststainless steel is about 0.35 at the ambient temperature and decreases abruptly to half of the normal state value whenthe temperature is below the superconducting transition temperature of Bi_(1.6)Pb_(0. 4_Srz_2Ca_2Cu_30_(10-x). Themeasurements prove directly the effect of electronic excitation on friction. Moreover, the Ag/Bi_(1.6) Pb_(0.4)Sr_2Ca_2Cu_3O_(10-x) composite samples were prepared by sintering Bi_(1.6)Pb_(0.4)Sr_2Ca_2Cu_3O_(10-x) with Ag at different mass fractions to improve the tribological properties of Bi_(1.6)Pb_(0.4)Sr_2Ca_2Cu_3O_(10-x) at room temperature. The experimental results show that the friction coefficient of 10 Wt%Ag/Bi_(1. 6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x) is about 0. 2~O. 3 and the wear rate is 4. 57×10~(-4)mm~3·(N·m)~(-1), and the superconductivity of 10 Wt% Ag/Bi_(1. 6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x) is not degenerated.%为适应20℃~-200℃温度的适用范围, 采用固相法制备了Bi_(1.6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x)超导材料, 用摩擦磨损试验机测试了Bi_(1.6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x)从液氮温度至室温的摩擦学性能. 结果表明: 在室温20℃下, Bi_(1. 6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x)与对偶件轴承钢盘对摩时, 摩擦系数约为0. 35, 当温度降到超导转变温度以下时(液氮温度-170℃)摩擦系数大幅度降低, Bi_(1. 6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x)超导态摩擦系数为正常态值的一半, 实验证明了电子激励对摩擦能量耗散的作用. 为改善室温下Bi_(1. 6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x)摩擦学性能, 掺杂不同质量分数Ag作为润滑组元, 制备了Ag/Bi_(1. 6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x)

  19. The effect of K-na co-doping on the formation and particle size of Bi-2212 phase

    Science.gov (United States)

    Kır, M. Ebru; Özkurt, Berdan; Aytekin, M. Ersin

    2016-06-01

    Superconducting K-Na co-doped Bi2Sr2KxCa1Cu1.75Na0.25Oy (x=0, 0.05, 0.1 and 0.25) ceramics are prepared by a solid-state reaction method. It is clearly determined from XRD data that the characteristic peaks of Bi-2212 phase are observed in all samples. The resistivity measurements show that Tc (onset) values is gradually increasing as K content is increased. It is also found that K-Na co-doping influence the grain sizes for Bi-2212 phase significantly. The critical current densities as a function of magnetic field have been calculated from M-H hysteresis loops of samples according to Bean's critical model, indicating that K-Na co-doping cause higher Jc values than the pure ones.

  20. Spectral investigation of hot-spot and cavity resonance effects on the terahertz radiation emitted from high-Tc superconducting Bi2Sr2CaCu2O8+δ single crystal mesa structures

    Science.gov (United States)

    Kadowaki, Kazuo; Watanabe, Chiharu; Minami, Hidetoshi; Yamamoto, Takashi; Kashiwagi, Takanari; Klemm, Richard

    2014-03-01

    Terahertz (THz) electromagnetic radiation emitted from high-Tc superconducting Bi2Sr2CaCu2O8+δ mesa structures in the case of single mesa and series-connected mesas is investigated by the FTIR spectroscopic technique while observing its temperature distribution simultaneously by a SiC photoluminescence technique. Changing the bias level, sudden jumps of the hot-spot position were clearly observed. Although the radiation intensity changes drastically associated with the jump of the hot spot position, the frequency is unaffected as long as the voltage per junction is kept constant. Since the frequency of the intense radiation satisfies the cavity resonance condition, we confirmed that the cavity resonance is of primarily importance for the synchronization of whole intrinsic Josephson junctions in the mesa for high power radiation. This work was supported in part by the Grant-in-Aid for challenging Exploratory Research, the Ministry of Education, Culture, Sports, Science & Technology (MEXT).

  1. Dielectric and piezoelectric properties of Bi0.5(Na0.82K0.18)0.5 TiO3–LiSbO3 lead-free piezoelectric ceramics

    Indian Academy of Sciences (India)

    Zhou Chong-Rong; Chai Li-Yuan

    2011-07-01

    The (1–)Bi0.5(Na0.82K0.18)0.5TiO3–LiSbO3 ( = 0−0.03) lead-free piezoelectric ceramics were fabricated by a conventional solid-state reaction method and the effect of LiSbO3 addition on microstructure and electrical properties of the ceramics was investigated. The results of XRD measurement show that Li+ and Sb5+ diffuse into the Bi0.5(Na0.82K0.18)0.5TiO3 lattices to form a solid solution with a pure perovskite structure. The LiSbO3 addition has no remarkable effect on the crystal structure. However, a significant change in grain size took place. Simultaneously, with increasing amount of LiSbO3, the temperature for a antiferroelectric to paraelectric phase transition clearly increases. The piezoelectric constant 33 and the electromechanical coupling factor p show an obvious improvement by adding small amount of LiSbO3, which shows optimum values of 33 = 175 pC/N and p = 0.36 at = 0.01.

  2. Dielectric, thermal and Raman spectroscopy studies of lead-free (Na0.5Bi0.5)1-xSrxTiO3 (x = 0, 0.04 and 0.06) ceramics

    Science.gov (United States)

    Suchanicz, J.; Bovtun, V.; Dutkiewicz, E. M.; Konieczny, K.; Sitko, D.; Kluczewska, K.; Wajda, A.; Kalvane, A.; Sternberg, A.

    2016-08-01

    Lead-free (Na0.5Bi0.5)1-xSrxTiO3 (x = 0, 0.04 and 0.06) ceramics with relative densities above 97% were prepared by solid-state synthesis process. Their dielectric, thermal and Raman properties were studied. X-ray diffraction analysis shows perovskite structure with rhombohedral symmetry at room temperature. Sr doping of Na0.5Bi0.5TiO3 (NBT) results in an increase of the dielectric permittivity, diffusing of the permittivity maximum and its shift toward lower temperatures. The temperature of the rhombohedral-tetragonal phase transition indicated by the differential scanning calorimetry (DSC) peak and relaxational dielectric anomaly near the depolarization temperature are also shifted toward lower temperatures. The observed increase and broadening of the permittivity maximum, enhancement of the dielectric relaxation near the depolarization temperature, broadening of the DSC anomaly related to the rhombohedral-tetragonal phase transition and broadening of the Raman bands with increasing Sr content are attributed to the increase of the degree of cationic disorder and evident enhancement of the relaxor-like features in NBT-xST. This enhancement could play a positive role in the improvement of the piezoelectric performance of NBT-based ceramics.

  3. Electric-field-temperature phase diagram of Mn-doped Bi{sub 0.5}(Na{sub 0.9}K{sub 0.1}){sub 0.5}TiO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Ehara, Yoshitaka, E-mail: Ehara@ceramics.tu-darmstadt.de; Novak, Nikola [Institute of Materials Science, Technische Universität Darmstadt, Darmstadt 64287 (Germany); Yasui, Shintaro; Itoh, Mitsuru [Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Webber, Kyle G. [Department of Materials Science, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91058 Erlangen (Germany)

    2015-12-28

    An electric field–temperature (E-T) phase diagram for a lead-free 0.5 mol. % Mn-doped Bi(Na{sub 0.1}K{sub 0.9})TiO{sub 3} ceramics was investigated. The x-ray diffraction, dielectric and polarization measurements revealed relaxor behavior and were used to characterize the stability regions of the non-ergodic relaxor, ergodic relaxor and electric field induced ferroelectric states. As indicated by the polarization–current density profiles, transformation between two electric fields, induced ferroelectric states with opposite polarization direction arise via a two-step process through an intermediate relaxor state. Interplay between the ferroelectric state conversion and intermediate relaxor state is governed by the dynamics of polarization relaxation. The presented E-T phase diagram revealed the effects of the applied electric field and temperature on stability regions. This is of special interest since the Bi{sub 0.5}(Na{sub 0.1}K{sub 0.9}){sub 0.5}TiO{sub 3} ceramics were proposed as a potential piezoceramic material.

  4. Composite metallic sheathes: the key to low-cost, high strength (Bi,Pb)2Sr2Ca2Cu3O10-based tapes?

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude

    2007-01-01

    (Bi, Pb)(2)Sr2Ca2Cu3O10-based superconducting tapes were prepared by the powder- in- tube process, using a bimetallic sheath consisting of Ag and Ni. Ag was in contact with the superconducting ceramic core and acted as a protective layer against reaction between the external Ni sheath and the core......(e) of about 11 000 A cm(-2), were achieved in a single heat-treatment. The efficient protection offered by the Ag layer against Ni diffusion into the ceramic core suggests that Ag layers as thin as 5 mu m may be applied, thus reducing the production costs. The superior stiffness of Ni provides a stronger...

  5. High Tc superconducting small loop antenna

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Z.; Mehler, M.J.; Maclean, T.S.M.; Lancaster, M.J.; Gough, C.E. (Univ. of Birmingham (UK)); Alford, N. (I.C.I. Advanced Materials Div., Runcorn (UK))

    1989-12-01

    The improvement in the radiation efficiency of an electrically small loop antenna is analysed when it is fabricated from a superconductor, and experimental results for a liquid nitrogen cooled, ceramic superconducting loop at 450MHz are presented. (orig.).

  6. Structures, phase transformations, and dielectric properties of (1-x)Bi{sub 2}Zn{sub 2/3}Nb{sub 4/3}O{sub 7}-xBi{sub 1.5}NiNb{sub 1.5}O{sub 7} pyrochlore ceramics prepared by aqueous sol-gel method

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Y.X.; Li, L.X., E-mail: lilingxia91@163.com; Dong, H.L.; Yu, S.H.; Xu, D.

    2015-02-15

    Highlights: • The sol-gel process was employed to produce (1-x)β-BZN-xBNN pre-nanopowders. • The phase structure evolution procedure in (1-x)β-BZN-xBNN system was determined. • A near-zero τ{sub ε} together with a high ε{sub r} was obtained at 900 °C. • The structure-dielectric property relationships of the ceramics were determined. - Abstract: As a candidate of thermostable low temperature co-fired ceramics (LTCC) material, (1-x)Bi{sub 2}Zn{sub 2/3}Nb{sub 4/3}O{sub 7}-xBi{sub 1.5}NiNb{sub 1.5}O{sub 7} (0.0 ⩽ x ⩽ 1.0) ceramics with improved dielectric properties have been prepared via aqueous sol-gel method. The relations of phase equilibrium, crystal structure and dielectric properties of the composites were investigated systematically. Phase transformation, from orthorhombic zirconolite-like to cubic pyrochlore structure, occured with the increasing Bi{sub 1.5}NiNb{sub 1.5}O{sub 7} content. The phase stability of the orthorhombic and cubic pyrochlore phase in the (1-x)β-BZN-xBNN system was dependent on the Bi{sup 3+} content as well as the distribution and variety of divalent cations, such as Ni{sup 2+}/Zn{sup 2+} ratio. The phase boundaries were located around x = 0.1 and x = 0.6 for orthorhombic and cubic phases, respectively. Near-zero temperature coefficient of dielectric constant (τ{sub ε}) was obtained and the dielectric constant (ε{sub r}) was in the range of 80-165 in this system, which were strongly correlated with phase composition. The (1-x)β-BZN-xBNN ceramic with x = 0.2 satisfied the EIA (Electronic Industries Association) specification NP0 (τ{sub ε}≤± 30 ppm/°C between -55 and 125 °C) exhibited excellent dielectric properties of ε{sub r} = 105.6, small dielectric tangent (tan δ) ∼ 10{sup -4}, τ{sub ε} = -11.1 ppm/°C with the low-firing temperature of 900 °C within the two-phase region, which can be a promising candidate for LTCC and multilayer components applications in high frequency and microwave range.

  7. Needle-like microstructure in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+x}

    Energy Technology Data Exchange (ETDEWEB)

    Cabeza, O.; Barca, O.; Miguelez, F. [Univ. de A Coruna (Spain)

    1997-06-01

    The authors have obtained superconducting Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+x} ceramic compounds with a grain structure that consists of needle-like particles of about 1.5 mm in length and 100 {mu}m in diameter, which seem to be formed by flake-like small grains. The Bi(2212) compound has been prepared following the polymer solution synthesis method. The thermal treatment used is a simplified version of the melt-textured growth process (MTG), with the sample placed in a zone of a simple tube furnace where the temperature gradient was about 15{degrees}C/cm. The authors have performed scanning electron microscopy (SEM) observations on the samples, before and after thermal treatment. In addition, they have measured the ac susceptibility of both samples to confirm their superconducting nature and critical temperatures of about 91 K.

  8. Study on Far-Infrared Reflectivity Spectra of Microwave Dielectric Ceramic (RbBi) 1/2 MoO4%(RbBi)1/2MoO4陶瓷微波介电性能的远红外反射谱研究

    Institute of Scientific and Technical Information of China (English)

    王秋萍; 刘汉臣

    2012-01-01

    The (RbBi)1/2MoO4 ceramic was prepared via solid state reaction method. The room temperature far-infrared reflectivity spectra were measured and 15 vibration modes were observed. Kramers-Kronig (K-K) relationship was employed to fit infrared spectra. The optical frequency permittivity ε00 is equal to 2. 17 for the dielectric materials, and the extrapolated value to microwave frequency (at about 9 GHz) is 20. 56 and it is slightly smaller than the actual measured value ~21. 4. The calculated value of quality factor (Q×f) is 11 790 GHz, which is higher than the actual measured value ~6 200 GHz, and it can be deduced that the quality factor of the (RbBi)1/2MoQt ceramic material has large room for improvement.%采用固相反应法制备了(RbBi)1/2 MoO4陶瓷样品.室温下测量了(RbBi)1/2 MoO4的红外反射谱,观察到15个振动模式;利用Kramers-Kronig(K-K)关系对样品的红外反射谱进行数据处理,获得材料的光频介电常数ε∞=2.17,微波频段的外推值为20.56,略小于实际测量值21.4;获得材料的本征品质因数Q×f为11790 GHz,高于实际测量值6200 GHz,说明陶瓷材料的品质因数还有较大提升空间.

  9. X-ray diffraction, dielectric, conduction and Raman studies in Na{sub 0.925}Bi{sub 0.075}Nb{sub 0.925}Mn{sub 0.075}O{sub 3} ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Chaker, Chiheb [Laboratoire des Materiaux Ferroelectriques (LMF), Unite de Recherche Physique-Mathematiques 05UR15-04, Universite de Sfax, Faculte des Sciences de Sfax, Route de Soukra km 3,5 - B.P.1171, 3000 Sfax (Tunisia); Laboratoire de Physique de la Matiere Condensee (LPMC), Universite de Picardie Jules Verne, Pole Scientifique, 33 rue Saint-Leu, 80039 Amiens Cedex 1 (France); Gagou, Y.; Dellis, J.-L.; El Marssi, M. [Laboratoire de Physique de la Matiere Condensee (LPMC), Universite de Picardie Jules Verne, Pole Scientifique, 33 rue Saint-Leu, 80039 Amiens Cedex 1 (France); Abdelmoula, N.; Khemakhem, H. [Laboratoire des Materiaux Ferroelectriques (LMF), Unite de Recherche Physique-Mathematiques 05UR15-04, Universite de Sfax, Faculte des Sciences de Sfax, Route de Soukra km 3,5 - B.P.1171, 3000 Sfax (Tunisia); Masquelier, C. [Laboratoire de Reactivite et Chimie des Solides (LRCS), UMR 6007, Universite de Picardie Jules Verne, Pole Scientifique, 33 rue Saint-Leu, 80039 Amiens Cedex 1 (France)

    2012-02-15

    Ceramic with composition Na{sub 0.925}Bi{sub 0.075}Nb{sub 0.925}Mn{sub 0.075}O{sub 3} (NNBM0075) was synthesized by high temperature solid state reaction technique. It was studied using X-ray diffraction (XRD), dielectric measurements and Raman spectroscopy. The sample crystallizes in orthorhombic perovskite structure with space group Pbma at room temperature. Dielectric properties of the ceramic was investigated in a broad range of temperatures (-150 to 450 deg. C) and frequencies (0.1-10{sup 3} kHz), and show two different anomalies connected to the symmetry change and electrical conductivity. Dielectric frequency dispersion phenomena in the NNBM0075 ceramic was analyzed by impedance spectroscopy in the temperature range from 55 to 425 deg. C. The Cole-Cole analysis based on electrical circuit and least square method was used to characterize the conduction phenomenon. A separation of the grain and grain boundary properties was achieved using an equivalent circuit model. The different parameters of this circuit were determined using impedance studies. Four conduction ranges, with different activation energies, were determined using the Arrhenius model. Raman spectra were studied as a function of temperatures and confirmed the X-ray and dielectric results. This composition is of interest for applications due to his physical properties and environmentally friendly character.

  10. Significantly enhanced ferroelectricity and magnetic properties in (Sr{sub 0.5}Ca{sub 0.5})TiO{sub 3}-modified BiFeO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Juan; Liu, Xiao Qiang, E-mail: xqliu@zju.edu.cn, E-mail: xmchen59@zju.edu.cn; Chen, Xiang Ming, E-mail: xqliu@zju.edu.cn, E-mail: xmchen59@zju.edu.cn [Laboratory of Dielectric Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

    2015-05-07

    BiFeO{sub 3} multiferroic ceramics were modified by introducing (Sr{sub 0.5}Ca{sub 0.5})TiO{sub 3} to form solid solutions. The single phase structure was easy to be obtained in Bi{sub 1−x}(Sr{sub 0.5}Ca{sub 0.5}){sub x}Fe{sub 1−x}Ti{sub x}O{sub 3} (x = 0.2, 0.25, 0.3, and 0.4) solid solutions. Rietveld refinement of X-ray diffraction data revealed a transition from rhombohedral R3c (x = 0.2, 0.25, and 0.3) to orthorhombic Pnma (x = 0.4). Current density-field (J-E) characteristics indicated that the leakage current density was reduced by three orders of magnitude in Bi{sub 1−x}(Sr{sub 0.5}Ca{sub 0.5}){sub x}Fe{sub 1−x}Ti{sub x}O{sub 3} ceramics. Both the ferroelectricity and magnetic properties were significantly enhanced in the present solid solutions. P-E hysteresis loop measurements with dynamic leakage current compensation methods showed the significantly enhanced ferroelectric properties for x = 0.25 and 0.3 and the paraelectric behavior for x = 0.4. The best ferromagnetic characteristics were achieved in the composition of x = 0.25, where the saturated M-H loop was determined with M{sub r} = 34.8 emu/mol. The improvement of ferroelectricity was mainly due to the suppressed leakage current, and the enhanced magnetism originated from the partial substitution of Fe{sup 3+} by Ti{sup 4+}, which destroyed its previous spiral structure to allow the appearance of a macroscopic magnetization.

  11. Ceramic synthesis of 0.08BiGaO3-0.90BaTiO3-0.02LiNbO3 under high pressure and high temperature

    Science.gov (United States)

    Hui, Jin; Yong, Li; Mou-Sheng, Song; Lin, Chen; Xiao-Peng, Jia; Hong-An, Ma

    2016-07-01

    In this paper, the preparation of 0.08BiGaO3-0.90BaTiO3-0.02LiNbO3 is investigated at pressure 3.8 GPa and temperature 1100-1200 °C. Experimental results indicate that not only is the sintered rate more effective, but also the sintered temperature is lower under high pressure and high temperature than those of under normal pressure. It is thought that the adscititious pressure plays the key role in this process, which is discussed in detail. The composition and the structure of the as-prepared samples are recorded by XRD patterns. The result shows that the phases of BaTiO3, BaBiO2.77, and Ba2Bi4Ti5O18 with piezoelectric ceramic performance generate in the sintered samples. Furthermore, the surface morphology characteristics of the typical samples are also investigated using a scanning electron microscope. It indicates that the grain size and surface structure of the samples are closely related to the sintering temperature and sintering time. It is hoped that this study can provide a new train of thought for the preparation of lead-free piezoelectric ceramics with excellent performance. Project supported by the National Natural Science Foundation of China (Grant No. 51172089), the Natural Science Foundation of Education Department of Guizhou Province, China (Grant Nos. KY [2013]183 and LH [2015]7232), and the Research Fund for the Doctoral Program of Tongren University, China (Grant No. DS1302).

  12. Structure-property relationships of novel microwave dielectric ceramics with low sintering temperatures: (Na(0.5x)Bi(0.5x)Ca(1-x))MoO(4).

    Science.gov (United States)

    Guo, Jing; Zhou, Di; Li, Yong; Shao, Tao; Qi, Ze-Ming; Jin, Biao-Bing; Wang, Hong

    2014-08-21

    A novel series of microwave dielectric ceramics (Na0.5xBi0.5xCa1-x)MoO4 (0 ≤ x ≤ 0.6) was synthesized by the solid state reaction method. The crystal structures, microstructures, dielectric responses, and vibrational properties were investigated using X-ray diffraction, scanning electron microscopy, a microwave network analyzer, and terahertz, Raman and infrared spectroscopies. All the samples could be sintered well below 850 °C and a scheelite solid solution could be formed without any secondary phase. At x = 0.5 and x = 0.6, low-firing (750-775 °C) high performance microwave dielectric materials were obtained with permittivities of 19.1-21.9, Q × f values of 20 660-22 700 GHz, and near-zero temperature coefficients. The factors affecting microwave dielectric properties were discussed based on the vibrational data. As revealed by Raman spectroscopy, the disorder degree grows with x rising, which might increase the permittivities and decrease the Q × f values. The infrared spectra were analyzed using the classical harmonic oscillator model, and the complex dielectric responses gained from the fits were extrapolated down to the microwave and THz range. It is believed that the external vibration modes located at low frequencies dominate the main dielectric polarization contributions, especially the Na-O/Bi-O translational mode. This result indicates that the microwave dielectric properties of (Na0.5xBi0.5xCa1-x)MoO4 ceramics mainly depend on the behavior of AO8 polyhedra.

  13. Preparation and characterization of Ag-added Bi1.84Pb0.4Sr2Ca2.2Cu3O10+ bulk tube conductors for cryogen free superconducting magnet

    Indian Academy of Sciences (India)

    S N Ekbote; G K Padam; M Sharma; N K Arora; B S Khurana; R C Goel; D K Suri; N Mehra; B K Das

    2001-12-01

    Bulk tube conductors of Bi1.84Pb0.4Sr2Ca2.2Cu3O10+ with addition of silver varying from 0 to 25 wt% (not reported earlier) were systematically studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), electrical transport and a.c. susceptibility techniques. The tube conductors formed by cold isostatic pressing (CIP) of the powders obtained from spray drying method have been made successfully. It was found that Ag addition has not only affected the formation of the desired Bi-2223 phase and the microstructure of these large bulk tube samples thereby influencing on the critical current (c), it also reduces the contact resistance to minimize the cryogen losses. These variations have been found to be Ag content dependent. An optimized value of 10 wt% Ag has been found to produce the best quality tubes showing reproducible c value > 120 Amp at 77 K which is in general a requirement to energies of the cryogen free conventional/HTSC superconducting magnets below 20 K.

  14. Superconductivity in La1-x Sm x O0.5F0.5BiS2 (x  =  0.2, 0.8) under hydrostatic pressure

    Science.gov (United States)

    Kalai Selvan, G.; Thakur, Gohil S.; Manikandan, K.; Banerjee, A.; Haque, Zeba; Gupta, L. C.; Ganguli, Ashok K.; Arumugam, S.

    2016-07-01

    We have investigated the pressure effect on the newly discovered samarium-doped La1-x Sm x O0.5F0.5BiS2 superconductors. More than a threefold increase in T c (10.3 K) is observed with external pressure (at ~1.74 GPa at a rate of 4.08 K GPa-1) for x  =  0.2 composition. There is a concomitant large improvement in the quality of the superconducting transition. Beyond this pressure T c decreases monotonously at the rate of  -2.09 K GPa-1. In the x  =  0.8 sample, we do not observe any enhancement in T c with the application of pressure (up to 1.76 GPa). The semiconducting behavior observed in the normal-state resistivity of both samples is significantly subdued with the application of pressure which, if interpreted by invoking the thermal activation process, implies that the activation energy gap of the carriers is significantly reduced with pressure. We believe these observations should generate further interest in La1-x Sm x O0.5F0.5BiS2 superconductors.

  15. The oxygen content of the high-temperature superconducting compound Bi{sub 2+x}Sr{sub 3-y}CayCu{sub 2}O{sub 8+d} with respect to varying Ca and Bi contents

    Energy Technology Data Exchange (ETDEWEB)

    Majewski, P.; Su, H.L.; Aldinger, F. [Max-Planck-Institut fuer Metallforschung, Stuggart (Germany)

    1994-12-31

    The oxygen content of Bi{sub 2+x}Sr{sub 3-y}Ca{sub y}Cu{sub 2}O{sub 8+d} (2212 phase) has been determined as a function of its cation concentration. With increasing Ca and Bi content the oxygen content increases and T{sub c} decreases. The oxygen content of Ca rich 2212 phase increases with decreasing annealing temperatures. The study shows that the T{sub c} of the 2212 phase primarily is controlled by its cation concentration.

  16. Electron-phonon superconductivity in LaO{sub 0.5}F{sub 0.5}BiSe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Yanqing; Du, Yongping; Wan, Xiangang, E-mail: xgwan@nju.edu.cn; Wang, Bogen [Department of Physics and National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Ding, Hang-Chen [Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai 200062 (China); Savrasov, Sergey Y. [Department of Physics, University of California, Davis, One Shields Avenue, Davis, California 95616 (United States); Duan, Chun-Gang [Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai 200062 (China); National Laboratory for Infrared Physics, Chinese Academy of Sciences, Shanghai 200083 (China)

    2014-06-21

    We report density functional calculations of the electronic structure, Fermi surface, phonon spectrum and electron–phonon coupling for the newly discovered superconductor LaO{sub 0.5}F{sub 0.5}BiSe{sub 2}. It is confirmed that there is a strong Fermi surface nesting at (π,π,0), which results in unstable phonon branches. Combining the frozen phonon total energy calculations and an anharmonic oscillator model, we find that the quantum fluctuation prevents the appearance of static long–range order. The calculation shows that LaO{sub 0.5}F{sub 0.5}BiSe{sub 2} is highly anisotropic, and same as its cousin LaO{sub 0.5}F{sub 0.5}BiS{sub 2}, this compound is also a conventional electron-phonon coupling induced superconductor.

  17. Influence of gold diffusion-doped on phase formation, superconducting and microstructure properties of Bi1.8Pb0.35Sr1.9Ca2.1Cu3Oy superconductors

    Science.gov (United States)

    Ozturk, O.; Akdogan, M.; Terzioglu, C.; Gencer, A.

    2009-03-01

    We report on low-field magnetic properties of gold diffusion-doped Bi1.8Pb0.35Sr1.9Ca2.1Cu3Oy superconducting bulk samples by performing ac susceptibility measurements. The undoped samples were prepared by the standard solid-state reaction method. Doping of Bi1.8Pb0.35Sr1.9Ca2.1Cu3Oy was carried out by means of Au-diffusion during sintering from an evaporated gold film on pellets. To investigate the effect of gold-diffusion and diffusion-annealing duration on transport, magnetic and microstructure properties of the superconducting samples we performed magnetoresistivity, scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements. The ac susceptibility as a function of temperature measurements were carried out at different values of the ac magnetic field amplitudes (Hac) in the range between 20A/m and 320 A/m for 211 Hz. The imaginary part of ac susceptibility measurements is used to calculate intergranular critical current density Jc(Tp) using the Bean Model. Jc(Tp) is seen to increase from 60 A cm-2 to 90 A cm-2 with increasing diffusion-annealing time from 10 h to 50 h. The peak temperature, Tp, in the imaginary part of the ac susceptibility is shifted to a lower temperature with decreasing diffusion-annealing duration as well as increasing ac magnetic fields. The force pinning density (αjj (0)) increased with increasing diffusion annealing time. The value of Tc in gold-diffused samples, in comparison with the undoped samples, increased from 100 ± 0.2 K to 104 ± 0.2 K. It was observed that the value of Tc-offset of the gold-doped samples enhanced with further increasing diffusion-annealing duration. XRD patterns and SEM micrographs are used to obtain information about Bi-2223 phase ratio, lattice parameters and grain size of the samples. Gold doping enhanced the formation high-Tc phase and increased the grain size. The possible reasons for the observed improvements in transport, microstructure and magnetic properties due to Au diffusion and

  18. Applied superconductivity

    CERN Document Server

    Newhouse, Vernon L

    1975-01-01

    Applied Superconductivity, Volume II, is part of a two-volume series on applied superconductivity. The first volume dealt with electronic applications and radiation detection, and contains a chapter on liquid helium refrigeration. The present volume discusses magnets, electromechanical applications, accelerators, and microwave and rf devices. The book opens with a chapter on high-field superconducting magnets, covering applications and magnet design. Subsequent chapters discuss superconductive machinery such as superconductive bearings and motors; rf superconducting devices; and future prospec

  19. CuO/V2O5-Codoped Bi3/2ZnNb3/2O7 (BZN) Ceramic for Embedded Capacitor Layer in Integrated LTCC Modules

    Science.gov (United States)

    Lee, Kyoungho; Kang, Seungjin

    2016-06-01

    Sintering additives for Bi3/2ZnNb3/2O7 (BZN) ceramic have been studied to facilitate use of BZN as a material for embedded decoupling capacitors in high-density multilayered low-temperature cofired ceramic (LTCC) modules for mobile communication systems and three-dimensional printing modules. Among the additives studied, a CuO/V2O5 mixture was the most promising for cofiring BZN ceramic with a commercial low-permittivity ( ɛ r) LTCC sheet (MLS-22; NEG Co., Japan) and Ag electrode. BZN codoped with 0.5 wt.% CuO/V2O5 was successfully densified at 860°C by reactive liquid-phase sintering, and the resulting dielectric properties were acceptable for use of the CuO/V2O5-codoped BZN for embedded capacitors in LTCC modules. The room-temperature permittivity ( ɛ r) of the CuO/V2O5-codoped BZN was 148 at 1 MHz, and the capacitance thermal stability was ±1.3% within the temperature range of -55°C to 125°C. The physical and chemical compatibilities of the CuO/V2O5-codoped BZN with heterogeneous layers (low- ɛ r LTCC layer and Ag electrode layer) in LTCC modules were also examined. A cofiring test of the doped BZN ceramic with MLS-22 LTCC sheet revealed that thickness control of the two heterogeneous layers was a key factor to avoid crack formation during cofiring. The optimum thickness ratio of doped BZN to MLS-22 layers was less than 0.25:1. A chemical compatibility test revealed no severe reaction between the doped BZN/MLS-22 and doped BZN/Ag layers.

  20. Effect of Ag2O addition on the intergranular properties of the superconducting Bi-(Pb)-Sr-Ca-Cu-O system

    Science.gov (United States)

    Karaca, I.; Çelebi, S.; Varilci, A.; Malik, A. I.

    2003-01-01

    The effect of Ag2O addition on the Bi-(Pb)-Sr-Ca-Cu-O system has been investigated in terms of ac susceptibility, phase evolution, critical current density and critical temperature. It was found that as the amount of Ag2O addition increases, the intergranular critical current density decreases in our samples (Bi1.84Pb0.34Sr1.91Ca2.03Cu3.06O10) fabricated by ammonium nitrate technique. The analysis for comparison is based on the suppression degree of the diamagnetic behaviour with respect to fields, rapid or slow shift of the summit in chi'(T) to lower temperature with increasing field amplitude and the sharpness of the transition of chi'(T) for intergranular component for the same field amplitude. We also qualitatively discuss experimental results in the framework of the critical state model. The room temperature XRD diagram indicates the presence of large amount of high-Tc (2223) phase. The percentage of Bi-2223 phase in the phase mixture was estimated from the intensities of high-Tc (2223) and low-Tc (2212) phase peaks as 78% for the pure BSCCO sample. Among the Ag2O-added BSCCO samples studied, the one in which 5 wt%Ag2O was added shows the highest rate of Bi-2223 formation as 92%. The SEM analysis reveals some morphological changes induced by silver addition.

  1. Composition, microstructures, and magnetic properties of Bi-modified NiCuZn-ferrite for low temperature Co-fired ceramic application

    Science.gov (United States)

    Zhang, Suna; Jia, Lijun; Zhang, Huaiwu; Li, Jie; Zhou, Tingchuan; Liu, Baoyuan

    2014-05-01

    The effects of Ni2+ and Bi3+ substitution on the microstructural development and magnetic properties of low-temperature-fired NiCuZn ferrites with nominal compositions of NixCu0.21 Zn0.79-xBiyFe2-yO4 (x = 0.1-0.5, y = 0-0.05) were investigated in order to develop low-temperature-cofired ferrite technology and to produce high-frequency devices with a multilayer process. For the Bi-modified NiCuZn ferrites, increasing x decreased the average grain size due to lattice contraction; meanwhile, the saturation flux density first increased and then decreased. We attributed this behavior to the change of superexchange between A-B sites and B-B sites in the spinel structure. We found that Bi3+ ions could enter into the ferrite lattice, which enhanced the grain growth and densification during sintering due to the activation of the lattice. A study of the solid-state reaction kinetics of Bi-modified NiCuZn ferrites revealed that Bi3+ modification decreased the early activation temperature and the ferrite formation temperature; thus, Bi3+ modification could reduce the activation energy of the solid-state reaction. The Bi-substituted samples with x = 0.35 and y = 0.02 had compact, uniform microstructures, and high sintering densities, leading to relatively high values of permeability and Q-factor.

  2. 传输电流法测量Bi222/Ag多芯高温超导带材的交流损耗%AC Losses of Bi2223/Ag Superconducting Tape Measured by Transport Current Method

    Institute of Scientific and Technical Information of China (English)

    胡立发; 周廉; 王金星; 张平祥; 李成山; 扬仕钟; 何砚发; 李景会

    2001-01-01

    利用传输电流法设计了一套高温超导体自场损耗测量系统,样品上负载的传输电流幅值可以达到100A,频率在0.5 Hz到1 000Hz之间任意可调.测量了Bi2223/Ag高温超导带材在77 K不同频率条件下的自场交流损耗.并将实验结果与Norris方程的预期值进行了比较.发现当传输电流的频率较低时,Bi2223/Ag的交流损耗主要是磁滞损耗;而当频率较高时耦合损耗不能忽略.

  3. Superconductivity in the Sn-Ba-Sr-Y-Cu-O system

    Science.gov (United States)

    Aleksandrov, K. S.; Khrustalev, B. P.; Krivomazov, S. N.; Petrov, M. I.; Vasilyev, A. D.; Zwegintsev, S. A.

    1991-01-01

    After the discovery of high-T(sub c) superconductivity in the La-Ba-Cu-O compound, several families of superconducting oxides were synthesized. Here, researchers report the results of the search for superconductivity in the compounds based on tin which has a lone electron pair like Bi, Tl, and Pb. The following compounds were synthesized: Sn1Ba1Sr1Cu3O(sub x), Sn1Ba1Ca1Cu3O(sub x), Sn1Ba1Mg1Cu3O(sub x), Sn1Sr1Ca1Cu3O(sub x), Sn1Sr1Mg1Cu3O(sub x), and Sn1Ca1Mg1Cu3O(sub x). The initial components were oxides and carbonates of the appropriate elements. A standard firing-grinding procedure was used. Final heating was carried out at 960 C during 12 hours. Then the samples were cooled inside the furnace. All the synthesis cycles were carried out in air atmosphere. Among the synthesized compounds only Sn1Ba1Sr1Cu3O(sub x) showed remarkable conductivity. Other compounds were practically dielectrics. Presence of a possible superconductivity in Sn1Ba1Sr1Cu3O(sub x) was defined by using the Meissner effect. At low temperature a deviation from paramagnetic behavior is observed. The hysteresis loops obtained at lower temperature undoubtly testify to the presence of a superconductive phase in the sample. However, the part of the superconductive phase in the Sn1Ba1Sr1Cu3O(sub x) ceramic turned out to be small, less than 2 percent, which agrees with the estimation from magnetic data. In order to increase the content of the superconductive phase, two-valent cations Ba and Sr were partially substituted by univalent (K) and three-valent ones (Y).

  4. Effect of Electric Field and Temperature on Average Structure and Domain Wall Motion in 0.93Bi0.5Na0.5TiO3-0.07BaTiO3 Ceramic

    Directory of Open Access Journals (Sweden)

    Jian Wang

    2013-01-01

    Full Text Available In situ neutron powder diffraction patterns and dielectric spectra of 0.93Bi0.5Na0.5TiO3-0.07BaTiO3 ceramic were investigated under different electrical fields and temperatures. An electric-field-induced phase transition from metrically cubic to metrically tetragonal, associated with strong domain wall motion, occurs. Such induced phase and domain wall motion are unchanged until the high-temperature phase transition occurs from metrically tetragonal to metrically cubic. All these changes are irrelevant to the observed depolarization temperature (75°C. The depolarization behaviour is thus suggested to be associated with the local structure caused by the octahedral tilt twinning disorder.

  5. Comparison of the electrical properties of the new conductor Pr{sub 0.5}Bi{sub 0.05}Li{sub 0.35}TiO{sub 3} prepared by sol-gel and ceramic methods

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Sanchez, M.F. [IMRE, Universidad de la Habana, Ciudad de la Habana (Cuba); Fernandez, Nestor [Departamento de Quimica Inorganica, Universidad de la Habana, Ciudad de la Habana (Cuba); Martinez-Sarrion, Maria-Luisa; Mestres, Lourdes; Herraiz, Marta [Departament de Quimica Inorganica, Universitat de Barcelona, Barcelona (Spain); Escribano, Purificacion; Cordoncillo, Eloisa; Beltran, Hector [Departament de Quimica Inorganica y Organica, Universitat Jaume I, Castellon de la Plana (Spain)

    2005-07-01

    Lithium ion conducting perovskite, Pr{sub 0.5}Bi{sub 0.05}Li{sub 0.35}TiO{sub 3}, has been synthesized by ceramic and sol-gel methods. The influence of the synthesis method on the crystal structure, morphology and ionic conductivity has been studied. Crystal structure of the material prepared by the sol-gel method is identical to that of the material prepared by the solid state reaction, although the synthesis temperature in the former case is lower. AC impedance measurements show two contributions to the ionic conductivity, which can be ascribed to grain and grain boundary effects. The bulk conductivity is similar for samples obtained by each methods. The grain boundary conductivity, and therefore the total conductivity, is higher for samples prepared by the sol-gel method. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. 饰瓷对磨牙e.max双层全瓷冠断裂类型的影响%Influence of Veneering on Failure Behavior of e. max Bi- layered All- ceramic Molar Crowns. P

    Institute of Scientific and Technical Information of China (English)

    潘娱; Michael V Swain; 马骁; 张新平; 赵克

    2011-01-01

    目的:通过抗折破坏实验研究饰瓷对磨牙e.max双层全瓷冠断裂强度和断裂类型的影响,为减少临床双层全瓷修复体崩瓷提供实验依据.方法:制作单层全瓷冠(IPS e.max Press)和双层全瓷冠(IPS e.max Press/Ceram)共40个(每组20个),粘接于树脂代型后进行抗折破坏实验并记录断裂强度值;体视显微镜和扫描电子显微镜下观察断裂类型;能谱分析饰瓷-核瓷界面化学元素构成.结果:单层全瓷冠断裂强度值[(2665.4±759.2)N]与双层全瓷冠[(1431.1±404.3)N]间差异有统计学意义(P=0.000).饰瓷内部及饰瓷-核瓷界面缺陷催生裂纹造成饰瓷崩裂是双层全瓷冠断裂的主要模式.结论:饰瓷对磨牙e.max双层全瓷冠断裂强度和断裂类型均有影响;饰瓷内部及饰瓷-核瓷界面缺陷是全瓷冠断裂的主要原因,提高饰瓷断裂强度及减少界面缺陷可减少因崩瓷造成的修复体失败.%Objective: To evaluate the effect of veneering on fracture strength and failure mode of e. max bi-layered all-ceramic molar crowns, so as to provide an experimental basis for reducing veneer chipping and delamination in clinical situations. Methods: Forty all-ceramic molar crowns (IPSe. max Press) were fabricated in two groups (with and without veneering) and each group consists of twenty identical crowns. The crowns were seated on composite resin dies by adhesion and then the specimens were loaded to failure by using a universal mechanical testing machine under compressive load. Fractographic morphology and fracture mode of the failed specimens were observed by a stereomicroscope and a scanning electron microscope (SEM), and the compositions of the veneer-core interface were analyzed by energy dispersive spectroscopy (EDS). Result: Statistical analysis results indicated a significant difference of the mean fracture strength between mono-layered group (2665.4±759.2 N) and bi-layered group (1431.1±404.3 N, P=0.000). The bi-layered crowns

  7. Strain control of composite superconductors to prevent degradation of superconducting magnets due to a quench: I. Ag/Bi2Sr2CaCu2Ox multifilament round wires

    Science.gov (United States)

    Ye, Liyang; Li, Pei; Jaroszynski, Jan; Schwartz, Justin; Shen, Tengming

    2017-02-01

    The critical current of many practical superconductors is sensitive to strain, and this sensitivity is exacerbated during a quench that induces a peak local strain which can be fatal to superconducting magnets. Here, a new method is introduced to quantify the influence of the conductor stress and strain state during normal operation on the margin to degradation during a quench, as measured by the maximum allowable hot spot temperature T allowable, for composite wires within superconducting magnets. The first conductor examined is Ag-sheathed Bi2Sr2CaCu2Ox round wire carrying high engineering critical current density, J E, of 550 A mm-2 at 4.2 K and 15 T. The critical axial tensile stress of this conductor is determined to be 150 MPa and, in the absence of Lorentz forces, T allowable is greater than 450 K. With increasing axial tensile stress, σ a, however, T allowable decreases nonlinearly, dropping to 280 K for σ a = 120 MPa and to 160 K for σ a = 145 MPa. T allowable(σ a) is shown to be nonlinear and independent of magnetic field from 15 to 30 T. T allowable(σ a) dictates the balance between magnetic field generation, which increases with the magnet operating current and stress, and the safety margin, which decreases with decreasing T allowable, and therefore has important engineering value. It is also shown that T allowable(σ a) can be predicted accurately by a general strain model, showing that strain control is the key to preventing degradation of superconductors during a quench.

  8. The Investigation of Ba_(6-3x)(Nd_(1-y)Bi_y)_(8+2x)Ti_(18)O_(54) Microwave Dielectric Ceramics%Ba_(6-3x)(Nd_(1-y)Bi_y)_(8+2x)Ti_(18)O_(54)系微波介电陶瓷的研究

    Institute of Scientific and Technical Information of China (English)

    王爽

    2009-01-01

    研究了Ba_(6-3x)(Nd_(1-y)Bi_y)_(8+2x)Ti_(18)O_(54)(x=0~1)陶瓷微波性能,并对其微观机理和晶体结构进行分析.随Bi_2O_3含量的增加,系统介电常数(ε)迅速增大,品质因数与频率的乘积(Q·f)逐渐减小.掺入Bi_2O_3后,系统中出现具有高ε的Bi_4Ti_3O_(12)晶相,并形成了类填满型钨青铜结构,阳离子极化增强,因此ε随Bi_2O_3含量的增加而增大.实验表明,当y=0.25~0.3时,Ba_(6-3x)(Nd_(1-y)Bi_y)_(8+2x)Ti_(18)O_(54)(x =0~1) 陶瓷具有优良的微波介电性能,其主要工艺条件和性能参数为烧结温度1 200 ℃保温4 h,ε≈102~107,Q·f≈20 000~22 000 GHz(1 GHz测量), 容量温度系数|α_c|<10×10~(-6)/℃.%The microwave properties of Ba_(6-3x)(Nd_(1-y)Bi_y)_(8+2x)Ti_(18)O_(54)(x =0~1)system were investigated,and the micro-mechanism and the crystal structure were analyzed.The results indicated that the dielectric constant increased greatly while the Q·f value decreased with the increase of Bi_2O_3 content.These phenomena were related to the appearance of a new phase Bi_4Ti_3O_(12),which has high dielectric constant. Besides, full-filled tungsten bronze-like structure should be formed,the polarization of positive ions were enhanced.So,the samples doped with Bi_2O_3 presented higher dielectric constant.The experimental results showed that Ba_(6-3x)(Nd_(1-y)Bi_y)_(8+2x)Ti_(18)O_(54) ceramics exhibited excellent microwave dielectric properties at y=0.25~0.3.The main technological conditions and the parameters were as follows: the sintering temperature of 1 200 ℃,the holding time of 4 h,ε≈102~107,Q·f≈20 000~22 000 GHz(Measured at 1 GHz) and the capacity-temperature coefficient of |α_c|<10×10~(-6)/℃.

  9. A PRIVILEGED CITY ESKISEHiR IN TERMS OF THE PARK AND GARDEN CERAMICS AND A CONVERSATION WITH PROF. BiLGEHAN UZUNER

    Directory of Open Access Journals (Sweden)

    Burak Yıldırım

    2014-12-01

    Full Text Available Parks and gardens are always the important places for us. During our history, they have creatured the culturel communication environments, universalizing the artistic and aesthetic consciousness, enabling to develop the protecting awareness of the ecological balance, helping people getting rid from crowded cities and distressing mood and have enabled to stay cheek by jowl with the nature in this places, the designs entwined with nature and artistic works are now a days very important. We are able to see the use of the common and advanced form of parks and gardens from 1960 to the present and their examples made for various purposes in many countries of the world. Today, in our country and around the world, a lot of ceramic artists have been still producing realistic, stylizedor abstract sculptures, monuments, benches, wallboards, birdhouses, pools, fountains and waterjets on behalf of park-garden and these ceramics support contemporary architecture, interiordesign, landscape architecture, urban and regional planning areas and these are functional and decorative ceramics. In our country, compared to cities in other European countries, the production of the ceramics such as parks-gardens are insufficient except for big cities such as İstanbul, İzmir, Ankara. But in this context Eskişehir has a privileged place. Eskişehir is a city of art. Because the city has ceramic works, having been produced in the International Terra Cotta Symposium since 2001 and the city has been decorated these ceramic Works in many public gardens and parking area. This symposium has been arranged by Eskişehir Anadolu University Faculty of Fine Arts Professor Bilgehan Uzuner.

  10. Spectroscopic Fingerprint of Phase-Incoherent Superconductivity in the Underdoped Bi2Sr2CaCu2O8+δ

    Energy Technology Data Exchange (ETDEWEB)

    Lee, J.; Davis, J.; Fujita, K.; Schmidt, A.R.; Kim, C.K.; Eisaki, H.; Uchida, S.

    2009-08-28

    A possible explanation for the existence of the cuprate 'pseudogap' state is that it is a d-wave superconductor without quantum phase rigidity. Transport and thermodynamic studies provide compelling evidence that supports this proposal, but few spectroscopic explorations of it have been made. One spectroscopic signature of d-wave superconductivity is the particle-hole symmetric 'octet' of dispersive Bogoliubov quasiparticle interference modulations. Here we report on this octet's evolution from low temperatures to well into the underdoped pseudogap regime. No pronounced changes occur in the octet phenomenology at the superconductor's critical temperature T{sub c}, and it survives up to at least temperature T {approx} 1.5 T{sub c}. In this pseudogap regime, we observe the detailed phenomenology that was theoretically predicted for quasiparticle interference in a phase-incoherent d-wave superconductor. Thus, our results not only provide spectroscopic evidence to confirm and extend the transport and thermodynamics studies, but they also open the way for spectroscopic explorations of phase fluctuation rates, their effects on the Fermi arc, and the fundamental source of the phase fluctuations that suppress superconductivity in underdoped cuprates.

  11. Effect of microwave-enhanced superconductivity in YBa{sub 2}Cu{sub 3}O{sub 7} bi-crystalline grain boundary weak-links

    Energy Technology Data Exchange (ETDEWEB)

    Fu, C.M.; Chen, C.M.; Lin, H.C. [National Chiao-Tung Univ., Taiwan (China)] [and others

    1994-12-31

    We have studied systematically the effect of microwave irradiation on the temperature dependent resistivity R(T) and the current-voltage (I-V) characteristics of YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) bicrystalline grain boundary weak-links (GBWLs), with grain boundary of three different tilt angles. The superconducting transition temperature, T{sub c}, has significant enhancement upon microwave irradiation. The microwave enhanced T{sub c} is increased as a function of incidence microwave power, but limited to an optimum power level. The GBWLs of 45{degrees} tilt boundary has shown to be most sensitive to the microwave irradiation power, and the GBWLs of 36.8{degrees} tilt boundary has displayed a moderate response. In contrast, no enhancement of T{sub c} was observed in the GBWLs of 24{degrees} tilt boundary, as well as in the uniform films. Under the microwave irradiation, the R(T) dependence is hysteretic as the transition taken from superconducting state to normal state and vice versa. Mechanisms associated with the redistribution of nonequilibrium quasiparticles under microwave irradiation are discussed.

  12. Studies of electrical conductivity and complex initial permeability of multiferroic xBa0.95Sr0.05TiO3-(1-x)BiFe0.90Gd0.10O3 ceramics

    Science.gov (United States)

    Miah, Mohammad J.; Khan, M. N. I.; Hossain, A. K. M. Akther

    2016-07-01

    Multiferroic xBa0.95Sr0.05TiO3-(1-x)BiFe0.90Gd0.10O3 [xBST-(1-x)BFGO] (x = 0.00, 0.10 and 0.20) ceramics were prepared by the standard solid-state reaction technique. Crystal structure of the ceramics was determined by X-ray diffraction pattern. All the compositions exhibited rhombohedral crystal structure. The tolerance factor `t' varied from 0.847 to 0.864. The AC conductivity spectrum followed the Jonscher's power law. The Nyquist plots indicated that only grains have the contribution to the resistance in this material and the values of grain resistance (Rg) increased with BST content. The real part of complex initial permeability decreased with the increase in frequency and increased with increasing BST content. Magnetoelectric coefficient was determined for all compositions. The maximum value of magnetoelectric coefficient was found to be 1.467 mV.cm-1.Oe-1 for x = 0.20.

  13. Effects of Li Substitution and Sintering Temperature on Properties of Bi0.5(Na,K)0.5TiO3 Lead-Free Piezoelectric Ceramics

    Institute of Scientific and Technical Information of China (English)

    MING Bao-Quan; WANG Jin-Feng; ZANG Guo-Zhong

    2008-01-01

    Bi0.5 (Na0.72K0.28-xLix)0.5 TiO3 (BNKLT-100x) lead-free piezoelectric ceramics are synthesized by conventional solid state sintering techniques. The dielectric and piezoelectric properties of the BNKLT-100x ceramics as a function of Li content are systematically investigated. It is found that not only Li content but also the sintering temperature has a strong effect on the piezoelectric properties of BNKLT. The piezoelectric constant d33 of BNKLT varies from 120 to 252pC/N in the Li content range from 0.03 to 0.16. In the sintering temperature range from 1080 to 1130℃, the d33 value of BNKLT-6 changes from 200pC/N to 252pC/N. The BNKLT-6 sample sintered at 1100℃ has the highest piezoelectric constant d33 Of 252pC/N, with the electromechanical coupling factors kp of 0.32 and kt of 0.44.

  14. A Temperature-Insensitive Ba3.75Nd9.5Ti17.5(Cr0.5Nb0.5)0.5O54 Microwave Dielectric Ceramic by Bi3+ Substitution

    Science.gov (United States)

    Chen, Hetuo; Tang, Bin; Guo, Xia; Wei, Meng; Si, Feng; Yuan, Ying; Zhang, Shuren

    2017-02-01

    In this study, effects of Bi3+ substitution upon microwave dielectric properties of the (Cr0.5Nb0.5)4+ replaced Ba3.75Nd9.5Ti18O54 (0 ≤ x ≤ 0.2) ceramic have been reported. The x-ray diffraction (XRD) result shows a single phase for all compositions with peak position fluctuation. Within the whole x range, while the quality factor ( Q) is degraded, the dielectric constant ( ɛ r) can be improved by as high as 32% and the temperature coefficient of resonant frequency ( τ f) is tailored from around +40 ppm/°C to the vicinity of zero. Considering practical requirements, we can obtain a series of temperature-insensitive ceramics ( τ f ˜ 0 ppm/°C) with relative permittivity about 95 and Qf (defined as Q times the resonant frequency f) higher than 6000 GHz. They have the potential of being utilized in wireless microwave communication applications.

  15. Influence of size of seed grains and sintering condition on varistor properties of ZnO-Bi2O3-TiO2-Sb2O3 ceramics

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Varistor ceramics of ZnO-Bi2O3-TiO2-Sb2O3 system have been fabricated by introducing pre-fabricated ZnO seed grains with different size distributions respectively. The results show that the varistor properties were significantly influenced by the size of introduced seed grains, and introducing larger seed grains is more advantageous to the modification of microstructure and the improvement of varistor properties. The varistor properties were considerably improved with a moderately increased sintering temperature or time, whereas degraded apparently when the sintering temperature or time was excessively increased. Compared with the sintering time, the sintering temperature plays a more critical role in determining the varistor properties. By introducing pre-fabricated ZnO seed grains into the original powders, low-voltage ZnO varistor ceramics possessing the desired electrical properties have been produced with a sintering temperature of about 1  210  ℃ and a sintering temperature of 2~2.5  h.

  16. Effect of cerium substitution on structural and impedance properties of 0.8Ba0.2(Bi0.5K0.5)TiO3 lead free ceramic system

    Science.gov (United States)

    Ramesh, M. N. V.; Ramesh, K. V.

    2016-01-01

    Cerium-doped 0.8BaTiO3-0.2Bi0.5K0.5TiO3 with composition 0.8Ba0.2(Bi0.5K0.5)Ti1-xCexO3 where x = 0.01, 0.02, 0.03, 0.04, 0.05, 0.06 lead free ceramics were prepared by conventional solid state reaction method followed by high energy ball milling. X-ray diffraction studies confirm the tetragonal structure at room temperature for all the Ce-doped samples. Lattice parameters and density were increasing with increase of Ce doping. Frequency and temperature dependent dielectric studies were carried out and indicate that the dielectric constant and Curie temperature are decreasing with increasing of Ce doping. All the Ce-doped samples exhibiting diffused and dispersive phase transitions with degree of diffuseness ranging from 1.4 to 2 calculated from the modified Curie-Weiss law. Impedance studies confirms the temperature dependent non-Debye kind of relaxation process in the material. From the Cole-Cole plots measured at high temperatures, reveals that the grain effect in the all Ce-doped samples. Impedance analysis studies also support the X-ray diffraction and dielectric studies that occupation of Ce both at A-site and B-site for small values of Ce doping.

  17. Superconducting critical state of Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8]: two-dimensional effects at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, E. (Comision Nacional de Energia Atomica, Centro Atomico Bariloche (Argentina)); Goffman, M.F. (Comision Nacional de Energia Atomica, Centro Atomico Bariloche (Argentina)); Arribere, A. (Comision Nacional de Energia Atomica, Centro Atomico Bariloche (Argentina)); Cruz, F. de la (Comision Nacional de Energia Atomica, Centro Atomico Bariloche (Argentina)); Schneemeyer, L.F. (AT and T Bell Labs., Murray Hill, NJ (United States))

    1994-02-01

    The critical current in the c direction of Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8] is shown to increase with temperature in low temperature ZFC measurements. The results are consistent with a loss of the c direction long range phase correlation, induced by the temperature dependent critical current flowing in the ab planes. As a result of this and the loss of the long range correlation induced by thermal disorder, the low temperature electrical resistance of the ZFC critical state is finite at low temperatures, becomes zero and is finite again at higher temperature. (orig.)

  18. Synthesis of nano-structured Bi{sub 1−x}Ba{sub x}FeO{sub 3} ceramics with enhanced magnetic and electrical properties

    Energy Technology Data Exchange (ETDEWEB)

    Mostafavi, E., E-mail: ebi.mostafavi@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 14395-553, Tehran (Iran, Islamic Republic of); Ataie, A., E-mail: aataie@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 14395-553, Tehran (Iran, Islamic Republic of); Ahmadzadeh, M. [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 14395-553, Tehran (Iran, Islamic Republic of); Palizdar, M.; Comyn, T.P.; Bell, A.J. [Institute for Materials Research, University of Leeds LS2 9JT, Leeds (United Kingdom)

    2015-07-15

    Bi{sub 1−x}Ba{sub x}FeO{sub 3}(x = 0, 0.2) compounds were synthesized by conventional solid-state reaction method. Structural, morphological, magnetic and ferroelectric properties of the products were investigated systematically by employing X-ray diffraction, field emission scanning electron microscope, vibrating sample magnetometer as well as electrical evaluation techniques, respectively. The XRD results demonstrated distorted rhombohedral BiFeO{sub 3} crystal structure with the space group of R3c. However, 20wt% Ba doped sample underwent a structural phase transition from rhombohedral to distorted pseudo-cubic structure. FESEM images of the BiFeO{sub 3} sample calcined at 850 °C showed agglomerated nano-particles with a mean particle size of 60 nm, while Bi{sub 0.8}Ba{sub 0.2}FeO{sub 3} sample showed uniform cubic particles with a mean particle size of 220 nm. For Bi{sub 0.8}Ba{sub 0.2}FeO{sub 3} sample calcined at 850 °C, an anomaly in permittivity was observed in the vicinity of 370 °C which is around the Neel temperature of bismuth ferrite and is in agreement with the recent reports. - Graphical abstract: Display Omitted - Highlights: • Nano-structured Bi{sub 1−x}Ba{sub x}FeO{sub 3}(x = 0, 0.2) were synthesized by solid-state reaction. • Ferromagnetic, ferroelectric and dielectric properties enhanced with Ba doping. • The best properties obtained in calcined doped sample at 850 °C. • 20wt.% Ba-dopant change the structure of BFO from rhombohedral to pseudo-cubic.

  19. Impedance spectroscopy study of Na{sub 2}Nb{sub 4}O{sub 11} ceramic matrix by the addition of Bi{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, R.G.M.; Romeu, M.C. [Departamento de Engenharia de Teleinformática–UFC, Caixa Postal 6007, CEP 60755-640 Fortaleza, Ceará (Brazil); Costa, M.M., E-mail: maurocosta@pq.cnpq.br [Laboratório de Telecomunicações, Ciência e Engenharia dos Materiais (LOCEM), Caixa Postal 6030, CEP 60455-760 Fortaleza, Ceará (Brazil); Physics Department, Federal University of Mato Grosso-UFMT, 78060-900 Cuiabá, MT (Brazil); Silva, P.M.O; Filho, J.M.S. [Departamento de Engenharia de Teleinformática–UFC, Caixa Postal 6007, CEP 60755-640 Fortaleza, Ceará (Brazil); Junqueira, C.C.M. [Instituto de Aeronáutica e Espaço IAE, Praça Marechal Eduardo Gomes, 50, Vila das Acácias, CEP 12228-904 São José dos Campos, São Paulo (Brazil); Sombra, A.S.B., E-mail: sombra@ufc.com.br [Departamento de Engenharia de Teleinformática–UFC, Caixa Postal 6007, CEP 60755-640 Fortaleza, Ceará (Brazil); Laboratório de Telecomunicações, Ciência e Engenharia dos Materiais (LOCEM), Caixa Postal 6030, CEP 60455-760 Fortaleza, Ceará (Brazil)

    2014-01-25

    Highlights: • The structural, dielectric properties of the addition in the Na{sub 2}Nb{sub 4}O{sub 11}. • Complex impedance has been used to analyze the electrical and dielectric properties. • The modulus curves show a non-Debye behavior. -- Abstract: The effects of different additions of Bi{sub 2}O{sub 3} (0, 2, 5 and 10 wt.%) on Na{sub 2}Nb{sub 4}O{sub 11} ceramics have been studied by complex impedance spectroscopy analysis. The structural and dielectric properties of Na{sub 2}Nb{sub 4}O{sub 11}ceramics with Bi{sub 2}O{sub 3} additions are also discussed as a possible material for microwave and radio frequency applications. Solid state reaction method was used for producing the target compound. The present work also reports on sample preparation, where polyvinyl alcohol was used as a binder to reduce the brittleness and the organic binder was burnt out during sintering process. X-ray diffraction at room temperature was used to identify phases formed as well as optimum calcinations conditions the production of Na{sub 2}Nb{sub 4}O{sub 11} powder. Analysis was carried out to identify the pure-phase specimen by Rietveld refinement method. Based on this method a structure with the lattice parameters (a = 10.840 Å, b = 6.162 Å and c = 12.745 Å; α = 90°, β = 106.4° and γ = 90°) was found. The dielectric and electrical properties of Na{sub 2}Nb{sub 4}O{sub 11} for appropriate amounts of Bi{sub 2}O{sub 3} additions has showed a considerable enhancement and overriding applications for microwave and radio frequency communications. The electrical behavior (complex impedance Z{sup *}, complex modulus M{sup *}) were studied over a frequency range (1 Hz to 1 MHz) and temperature (553–713 K)

  20. Structure,Preparation and Application of Bi-system Superconducting Materials%YBCO材料的发展及其应用

    Institute of Scientific and Technical Information of China (English)

    王醒东; 徐华; 项飞; 张立永; 刘勇

    2012-01-01

    YBCO is one of important high temperature superconducting materials,which has been studied extensively in the past several decades.The paper summarized the research significance,discussed the structure,common forms and application of YBCO materials based on the literature at home and abroad,finally the applied prospects for the YBCO were introduced.%YBCO材料是重要的高温超导材料,在过去几十年里被广泛研究。本文概述了YBCO超导材料的研究意义,论述了其结构,总结了YBCO材料常见的几种形态及其应用,最后展望了YBCO材料的应用前景。

  1. Tailoring the structure and piezoelectric properties of BiFeO3-(K0.5Bi0.5)TiO3-PbTiO3 ceramics for high temperature applications

    Science.gov (United States)

    Bennett, J.; Bell, A. J.; Stevenson, T. J.; Comyn, T. P.

    2013-10-01

    There is a growing requirement for piezoelectric materials and systems which can operate in extreme environments, for example, oil & gas, and aerospace. Here, we present the high temperature BiFeO3-K0.5Bi0.5TiO3-PbTiO3 (BF-KBT-PT) polycrystalline perovskite system. X-ray diffraction, impedance analysis, and Berlincourt measurements reveal a large region of phase coexistence, which can be tailored to optimise performance; Tc and the tetragonal spontaneous strain correlate strongly with the PbTiO3 concentration. The highest temperature composition has a d33 of 140 pmV-1 with a Tc = 542 °C, occupying previously unchartered territory on the classical d33-TC plot.

  2. Experimental Research on Superconductively Jointed Multifilamentary Bi2223/Ag Tapes%Bi系银包套多芯带材焊接的实验研究

    Institute of Scientific and Technical Information of China (English)

    阎正; 王银顺; 徐景智; 杨景发; 赵庆勋; 李光; 于威; 马全喜

    2003-01-01

    Bi 2223/ Ag多芯高温超导带材的焊接技术进行实验研究.焊接采用单轴方向不同压力下进行压接;另外在压接后,对不同压力压接下的样品进行热处理.实验结果表明:在77 K自场条件下,超导接头在压应力约为1.96×107 N/m2和热处理温度约为850 ℃时,得到焊接接头具有最高临界电流,其自场下临界电流约为带材临界电流的85%.

  3. Superconducting transistor

    Science.gov (United States)

    Gray, Kenneth E.

    1979-01-01

    A superconducting transistor is formed by disposing three thin films of superconducting material in a planar parallel arrangement and insulating the films from each other by layers of insulating oxides to form two tunnel junctions. One junction is biased above twice the superconducting energy gap and the other is biased at less than twice the superconducting energy gap. Injection of quasiparticles into the center film by one junction provides a current gain in the second junction.

  4. Superconductivity and superconductive electronics

    Science.gov (United States)

    Beasley, M. R.

    1990-12-01

    The Stanford Center for Research on Superconductivity and Superconductive Electronics is currently focused on developing techniques for producing increasingly improved films and multilayers of the high-temperature superconductors, studying their physical properties and using these films and multilayers in device physics studies. In general the thin film synthesis work leads the way. Once a given film or multilayer structure can be made reasonably routinely, the emphasis shifts to studying the physical properties and device physics of these structures and on to the next level of film quality or multilayer complexity. The most advanced thin films synthesis work in the past year has involved developing techniques to deposit a-axis and c-axis YBCO/PBCO superlattices and related structures. The in-situ feature is desirable because no solid state reactions with accompanying changes in volume, morphology, etc., that degrade the quality of the film involved.

  5. Using a ceramic chamber in kicker magnets

    Energy Technology Data Exchange (ETDEWEB)

    Kurennoy, S.

    1993-05-01

    A ceramic chamber inside kicker magnets can provide the relevant field risetime. On the other hand, some metallic coating inside has to prevent static charge buildup and shield the beam from ceramic and ferrite at high frequencies to avoid possible resonances. The issues concerning the metallized ceramic chamber, such as coupling impedances and requirements on the coating, are studied to find a compromise solution for kickers of the Medium Energy Booster at the Superconducting Super Collider.

  6. Effect of cationic size in Hg(Tl/Bi)Ba2Ca2Cu3O8+ on superconducting and microstructural characteristics

    Indian Academy of Sciences (India)

    Rajiv Giri; H K Singh; R S Tiwari; O N Srivastava

    2001-10-01

    In this paper we have reported investigations on the effect of simultaneous substitution of Bi and Tl at the H site in the oxygen deficient HO layer of HBa2Ca2Cu3O8+ cuprate superconductor. Bulk polycrystalline samples have been prepared by the two-step solid state reaction process (precursor route). It has been observed that the as grown HBi0.2–TlBa2Ca2Cu3O8+ (with = 0.00, 0.05, 0.10, 0.15, 0.20) corresponds to the 1223 phase. It has been found that the c varies with the average cationic size $\\langle R_d \\rangle$ of the dopantcations. The optimum c of ∼ 131 K has been found for the composition HBi0.15Tl0.05Ba2Ca2Cu3O8+. This composition leads to the average dopant cation size of ∼ 1.108 Å which is very close to the size of H2+ (∼ 1.11 Å). The microstructure for HBi0.15Tl0.05Ba2Ca2Cu3O8+ has been found to be most dense and this phase exhibits the highest stability. The c of the optimum material HBi0.15Tl0.05Ba2Ca2Cu3O8+ is found to be ∼ 1.29 × 103 A/cm2 at 77 K.

  7. Influence of structural evolution on energy storage properties in Bi0.5Na0.5TiO3-SrTiO3-NaNbO3 lead-free ferroelectric ceramics

    Science.gov (United States)

    Li, Feng; Zhai, Jiwei; Shen, Bo; Liu, Xing; Yang, Ke; Zhang, Yang; Li, Peng; Liu, Baihui; Zeng, Huarong

    2017-02-01

    Lead-free (1-x)(0.8Bi0.5Na0.5TiO3-0.2SrTiO3)-xNaNbO3 (x = 0-0.1, abbreviated as BNT-ST-xNN) ceramics were fabricated by a conventional sintering route with pure perovskite phase via XRD analysis. Raman spectrum was exploited in order to give an insight into the variation of local structural evolution. All compositions exhibited an obvious evolution of dielectric relaxation behaviors. Dielectric and ferroelectric properties clarified that a crossover from nonergodic to ergodic relaxor properties was obtained with the addition of NN content. A relatively large energy storage density was obtained WRec ˜ 0.74 J/cm3 at 7 kV/mm for x = 0.05 at room temperature. Particularly, the energy storage properties exhibited temperature (25-160 °C) and frequency stability (0.1-20 Hz) with WRec around 0.6 J/cm3 at 6 kV/mm for x = 0.05 within the ergodic region. Pulsed discharging current waveforms were measured under different electric fields to detect the energy storage density and discharging speed behavior. An illustration of the charge-discharge process for the nonergodic and ergodic relaxor was depicted in order to disclose the difference of energy storage properties in BNT-ST-xNN system, and it is believed that this concept can be a guideline for fixing a position when designing a new energy-storage system for BNT-based relaxor ferroelectric ceramics.

  8. Interband electronic transitions and phase transformation of multiferroic Bi{sub 1−x}La{sub x}Fe{sub 1−y}Ti{sub y}O{sub 3} ceramics revealed by temperature-dependent spectroscopic ellipsometry

    Energy Technology Data Exchange (ETDEWEB)

    Xu, L. P.; Jiang, P. P.; Duan, Z. H.; Hu, Z. G., E-mail: zghu@ee.ecnu.edu.cn; Zhu, Z. Q.; Chu, J. H. [Key Laboratory of Polar Materials and Devices (MOE), Department of Electronic Engineering, East China Normal University, Shanghai 200241 (China); Zhang, L. L.; Yu, J. [Functional Material Research Laboratory, Tongji University, Shanghai 200092 (China)

    2013-12-21

    Optical properties and phase transition of Bi{sub 1−x}La{sub x}Fe{sub 1−y}Ti{sub y}O{sub 3} (BLFTO) ceramics with different composition (0.02 ≤ x ≤ 0.10, 0.01 ≤ y ≤ 0.06) have been investigated by spectroscopic ellipsometry (SE) in the temperature range of −70–450 °C. The real part of the complex dielectric function ε{sub 1} increases with the temperature. Meanwhile, the imaginary part ε{sub 2} in the low-energy region decreases with the temperature and has an opposite trend in the high-energy side. Four typical interband transitions (E{sub a} ∼ 2.50 eV, E{sub b} ∼ 2.70 eV, E{sub c} ∼ 3.60 eV, and E{sub d} ∼ 4.25 eV) can be observed from the second derivative of the complex dielectric functions with aid of the standard critical point model. The critical point (CP) transition becomes broadening and shifts to a lower energy side as La and Ti compositions increase. Moreover, the CP transition energies show a red-shift trend with increasing the temperature until 320 °C, due to the lattice thermal expansion and electron-phonon interaction. The typical interband transitions and partial spectral weight present anomalies in the proximity of antiferromagnetic transition owing to the coupling between magnetic and ferroelectric order parameters and spin-lattice coupling for BLFTO multiferroic materials. It was found that the Néel temperature of BLFTO ceramics decreases from 364 to 349 °C with increasing doping composition of La and Ti elements. These phenomena can be attributed to the modification of electronic structure and magnetic order because the differences of electronegativity and ionic radii between Bi and La, Fe and Ti induce the variations on the bond angle and bond length between cations and anions. Moreover, the substitution for magnetic Fe{sup 3+} ions with nonmagnetic Ti{sup 4+} ions can reduce the exchange interaction between adjacent magnetic moments. Therefore, SE technique can be sensitive for

  9. Scaling Behavior of AC Susceptibility of Multifilament Bi-2223/Ag Superconducting Tape%Bi-2223/Ag超导带材交流磁化率的标度行为研究

    Institute of Scientific and Technical Information of China (English)

    陈兴品; 李明亚; 刘庆; 韩征和

    2009-01-01

    Bi-2223/Ag多芯高温超导带材的交流磁化率的标度行为进行了探讨研究.测量了在外加磁场垂直于带材表面时,样品的交流磁化率与温度和磁场之间的关系.结果表明,外加交流磁场对实部和虚部的影响非常显著,交流磁化率的实部和虚部的转变宽度强烈依赖于外加磁场的大小.选择虚部峰值处的温度作为缩放参数,对实部和虚部的测量结果进行归一化处理,结果发现在外加磁场为(325~32.5)×10~(-4) T的条件下,所测量的全部交流磁化率的实部和虚部曲线都可以约化为一条曲线,得到一个普遍的标度律关系,在50~100 K的温度范围内,该交流磁化率的标度律关系与试验数据非常吻合,根据这一特性,推导出了铋系多芯高温超导带材的临界电流密度方程.

  10. Frequency-dependent impedance spectroscopy on the 0.925(Bi0.5Na0.40K0.10)TiO3-0.075(Ba0.70Sr0.30)TiO3 ceramic

    Science.gov (United States)

    Ullah, Amir; Rahman, Muneeb-ur; Iqbal, Muhammad Javid; Ahn, Chang Won; Kim, Ill Won; Ullah, Aman

    2016-06-01

    The electrical properties of the 0.925(Bi0.5(Na0.40K0.10)TiO3-0.075(Ba0.70Sr0.30)TiO3 (0.925BNKT-0.075BST) ceramic were investigated by using AC impedance spectroscopy over a wide range of frequencies (10 -2 ~ 105 Hz). The X-ray diffraction patterns confirmed the formation of a single-phase compound. A single semicircular arc in the impedance spectrum indicates that the main contribution of the bulk resistance ( R b ) were due to grain effects, with Rb decreasing with increasing temperature. The conductivity of the ceramics increased with increasing temperature, and the activation energy resulting from the DC conductivity was 0.86 eV. The ceramic displayed a typical negative temperature coefficient of resistance (NTCR) behavior, like that of a semiconductor.

  11. Portfolio: Ceramics.

    Science.gov (United States)

    Hardy, Jane; And Others

    1982-01-01

    Describes eight art activities using ceramics. Elementary students created ceramic tiles to depict ancient Egyptian and medieval European art, made ceramic cookie stamps, traced bisque plates on sketch paper, constructed clay room-tableaus, and designed clay relief masks. Secondary students pit-fired ceramic pots and designed ceramic Victorian…

  12. Magnetic and transport properties of superconducting (YBa sub 2 Cu sub 3 O sub 7-. delta. ) sub 1-x Ag sub x ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Laborde, O.; Guillot, M. (SNCI, CRTBT, Lab. de Crstallographie, C.N.R.S., 38 - Grenoble (France)); Souletie, B.; Lejay, P.; Tholence, J.L. (CRTBT, C.N.R.S., 38 - Grenoble (France)); Capponi, J.J. (Lab. de Cristallographie, C.N.R.S., 38 - Grenoble (France)); Ermolieff, A.; Marthon, S. (LETI, CENG, 38 - Grenoble (France)); Dwir, B.; Pavuna, D. (Swiss Federal Inst. of Tech., Lausanne (Switzerland))

    1989-12-01

    The introduction of silver in the intergranular space of YBa{sub 2}Cu{sub 3}O{sub 7} ceramics improves their normal state electrical and mechanical properties. We report here a study of such composites of which the grain size was found to increase with the annealing temperature, and goes through a maximum around 20% wt.silver for a constant annealing temperature (1000degC). Moreover, a maximum in the filling factor of YBa{sub 2}Cu{sub 3}O{sub 7} is found from a.c. susceptibility measurements for x {approx equal} 15% wt. of silver, which also corresponds to the maximum of the current density. The intergranular silver is found to improve the diamagnetic shielding in very low field. The irreversible fields, H{sub cs}, as determined by magnetoresistance are only decreased by {proportional to}10% for a composite containing {proportional to}15% weight of silver. (orig.).

  13. Influence of Compositions on the Dielectric Properties of CaBi4Ti4O15 Ceramics%组分影响CaBi4Ti4O15介电性能的研究

    Institute of Scientific and Technical Information of China (English)

    郑夏莲; 黄新友; 高春华

    2006-01-01

    采用正交设计试验法研究了配方对CaBi4Ti4O15(CBT)铁电陶瓷介电性能的影响,得到了影响CBT陶瓷介电性能的主次因素以及各因素水平影响其性能的趋势,进而得到了综合性能佳的CBT陶瓷.探讨了各组分对CBT陶瓷介电性能影响的机理,为CBT陶瓷材料的改性研究提供了依据.

  14. Elaboration and characterization of superconducting Bi:2223 ceramics with a view to fault current limiters; Elaboration et caracterisation de ceramiques supraconductrices Bi:2223 en vue de la limitation du courant

    Energy Technology Data Exchange (ETDEWEB)

    Noudem, J.G.; Porcar, L. [CNRS, Grenoble (France). EPM-Matformag]|[Schneider Electric S.A., Grenoble (France); Belmont, O.; Bourgault, D.; Tixador, P.; Beille, J.; Tournier, R. [CNRS, Grenoble (France). EPM-Matformag; Sanchez, J.; Barbut, J.M.; Barrault, M. [Schneider Electric S.A., Grenoble (France)

    1998-01-01

    High pulsed currents with a duration varying from 1.25 to 20 ms have been applied at 77 K to sintered and textured samples. For I > I{sub c}, two types of behaviour are observed: when the average temperature of the sample is lower than T{sub c}, a critical current is recovered at the end of the pulse. Above T{sub c}, samples remain normal after the pulse because the sample temperature is too high leading to a maximum instantaneous applied power up to 182 GW/m{sup 3} in the sintered sample. At 15I{sub c} electric fields of 400 V/m and 1000 V/m are observed for the sintered and textured samples respectively. (orig.). 5 refs.

  15. Low-temperature sintering and microwave dielectric properties of CuBi2(V2O5)-doped Li2O-ZnO-TiO2 ceramics%CuBi2(V2O5)掺杂Li2O-ZnO-TiO2系陶瓷的低温烧结和微波介电性能

    Institute of Scientific and Technical Information of China (English)

    何茗

    2015-01-01

    CuBi2(V2O5)(CBV for short) doped Li2O-ZnO-TiO2 system ceramics were prepared by the conventional solid-state reaction, using CuBi 2 (V 2 O 5 ) as sintering additive, which was common low melting point oxide. The behavior of sintering, phase composition, microstrceture and microwave dielectric properties of Li2O-ZnO-TiO2 system ceramics were characterized or measured by means of XRD and SEM. The results show that, the ceramic doped with 3.25%(mass fraction) CBV sintered at 875℃shows good microwave dielectric properties:εr=25.63,Q·f=53 400 GHz,τf=–5.27×10–6/℃.%以CuBi 2(V 2 O 5)(简称为CBV)低熔点氧化物为烧结助剂,采用传统的固相烧结工艺制备了CBV掺杂的Li2O-ZnO-TiO2系微波陶瓷。并利用XRD、SEM等研究了Li2O-ZnO-TiO2系陶瓷的烧结行为、物相组成、显微结构及微波介电性能等。结果表明:当CBV掺杂量为质量分数3.25%时,875℃烧结的Li 2 O-ZnO-TiO 2陶瓷微波具有良好的微波介电性能:εr=25.63,Q·f=53400 GHz,τf=–5.27×10–6/℃。

  16. Gd-substituted Bi-2223 superconductor

    Indian Academy of Sciences (India)

    D R Mishra

    2008-03-01

    The effects of gadolinium doping at calcium site on the normal and super-conducting properties of Bi-2223 system were studied. The Gd-doped (BiPb)-2223 series of specimens, namely Batch I, II and III were sintered at three different sintering temperatures 830, 850 and 895° C respectively. The properties investigated are (1) the normal state resistivity with a view to study metal-to-insulator transition, (2) the XRD patterns of the specimens with a view to study the relative composition of (BiPb)-2212 and (BiPb)-2223 phases and (3) the superconducting fluctuation behaviour (SFB) with a view to determine the effect of doping, if any, on the dimensionality of the fluctuation conductivity of the system. The normal state resistivity of Gd-substituted Bi-2223 specimens shows metallic, semiconducting and insulating behaviour. The c( = 0) values indicate that (BiPb)-2223 phase is responsible for the observed superconducting transitions in Batch I and Batch II specimens with Gd concentrations ≤ 0.7. This observation is further confirmed in the analysis of XRD patterns of these specimens. Gadolinium, being a magnetic impurity, has pair breaking effect near the Fermi level and decreases c( = 0). The analysis of the superconducting fluctuation behaviour (SFB) shows a 2D dimensionality without any cross-over.

  17. The study of the dependency of critical current density on cross section of sample in Bi1.6Pb0.4Sr2Ca2Cu3Oy and YBa2Cu3O7-& delta ceramic superconductors

    Directory of Open Access Journals (Sweden)

    M Zargar Shoushtari

    2006-09-01

    Full Text Available  In this paper, the effect of the cross-section on the critical current density (Jc of a sample in ceramic superconductors YBa2Cu3O7-­δ (YBCO and Bi1.6Pb0.4Sr2Ca2cu3Oy (BPSCCO has been studied. Five orthorhombic bar samples of YBCO with cross-sections of 6.25, 7.67, 9.25, 11.76, 14.67 mm2­ and also five orthorhombic bar samples of BPSCCO with cross-section of 6.4, 9.01, 11.88, 13.86, 14.98 mm2­ with the same synthesis conditions by the solid state reaction method were prepared. After the preparation of the samples, the Meissner effect, the critical temperature (Tc, and the critical current density (Jc measurements, XRD and SEM have been done on the samples. The results of XRD show that the dominant phase in YBCO and BPSCCO are 123 and 2223, respectively. The results of Jc measurements in 77 K show that in both superconductors, the Jc decreases with increasing of cross-section (A. The type of dissipation obeys a power law with the relation . For a given cross-section, Jc of the BPSCCO sample is smaller than the YBCO sample.

  18. Dielectric and impedance spectroscopic studies of 0.8BaTiO3-0.2Bi0.5K0.5TiO3 lead-free ceramics

    Science.gov (United States)

    Ramesh, M. N. V.; Ramesh, K. V.

    2015-06-01

    0.8BaTiO3-0.2Bi0.5K0.5TiO3 (BT-BKT20) lead-free ceramics were prepared by conventional solid state reaction method followed by high energy ball milling. The formation of a single phase tetragonal structure in the material was confirmed by X-ray diffraction. Frequency and temperature-dependent dielectric studies show relaxor behavior in the BT-BKT20 which was found to obey modified Curie-Weiss law with degree of diffuseness 1.573. Complex impedance and electric modulus spectroscopy studies reveal temperature-dependent relaxation process in the material. The Cole-Cole plots were measured at high temperatures at which grain effect was observed. Impedance and electric modulus spectroscopy studies show non-Debye kind of conductivity relaxation process in the present material. Activation energies were calculated from impedance and electric modulus spectroscopy and the values of activation energy indicated that the conduction is ionic in nature. AC and DC conductivity have been measured and studied at different temperatures.

  19. Dielectric and Ferroelectric Properties of Lead-Free [1-z{(Bi1-xLax0.5(Na1-yLiy0.5TiO3}-zBaTiO3] Ceramic System

    Directory of Open Access Journals (Sweden)

    Vijayeta Pal

    2013-01-01

    Full Text Available Lead-free specimens of [1-z{(Bi1-xLax0.5(Na1-yLiy0.5TiO3}-zBaTiO3] (BLNLT-BT, where x=0.04, y=0.025, and z=0, 0.02, 0.04, and 0.06 ceramic system were synthesized by a semiwet technique. In the present study, we have investigated the effect of Ba on the structure, morphology, and dielectric, ferroelectric, and piezoelectric properties of BLNLT system. The XRD patterns of all the specimens showed rhombohedral structure at room temperature. Field emission scanning electron microscopy images (FE-SEM showed grain growth inhibition with Ba content in BLNLT system. The temperature dependence of dielectric constant revealed that the temperature of maximum dielectric constant “Tm” and depolarization temperature “Td” decreased for the sample z=0.06 and showed high value of dielectric constant with low dielectric loss. These samples exhibited nonlinear behaviour of hysteresis loop. The values of dielectric constant (εr, dissipation factor (tan δ, piezo charge coefficient (d33, remnant polarization (Pr, and coercive field (Ec for the composition z=0.06 were 1495, 0.06, 20 pC/N, 5 μC/cm2, and 10.5 kV/cm, respectively.

  20. Field-induced phase transition in Bi{sub 1/2}Na{sub 1/2}TiO{sub 3}-based lead-free piezoelectric ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Hinterstein, Manuel [TU Darmstadt (Germany). Inst. for Materials Science; TU Dresden (Germany). Inst. for Materials Science; Knapp, Michael [CELLS, Barcelona (Spain); Hoelzel, Markus; Jo, Wook; Fuess, Hartmut [TU Darmstadt (Germany). Inst. for Materials Science; Cervellino, Antonio [Paul Scherrer Institute, Villigen (Switzerland). Swiss Light Source; Ehrenberg, Helmut [TU Dresden (Germany). Inst. for Materials Science

    2010-12-15

    The origin of the electric field-induced strain in the polycrystalline ceramic 0.92Bi{sub 1/2}Na{sub 1/2}TiO{sub 3}-0.06BaTiO{sub 3}-0.02K{sub 1/2}Na{sub 1/2}NbO{sub 3} was investigated using in situ high-resolution X-ray and neutron diffraction techniques. The initially existing tetragonal phase with pseudocubic lattice undergoes a reversible phase transition to a significantly distorted rhombohedral phase under electric field, accompanied by a change in the oxygen octahedral tilting from a{sup 0}a{sup 0}c{sup +} to a{sup -}a{sup -}a{sup -} and in the tilting angle. The polarization values for the tetragonal and rhombohedral phases were calculated based on the structural information from Rietveld refinements. The large recoverable electric field-induced strain is a consequence of a reversible electric field-induced phase transition from an almost nonpolar tetragonal phase to a ferroelectrically active rhombohedral phase. (orig.)

  1. Nonadiabatic small-polaron hopping conduction in Li-doped and undoped Bi4Sr3Ca3CuyOx (0<=y<=5)

    Science.gov (United States)

    Mollah, S.; Som, K. K.; Bose, K.; Chakravorty, A. K.; Chaudhuri, B. K.

    1992-11-01

    Detailed experimental results of temperature- and CuO-concentration-dependent dc conductivities of semiconducting Bi4Sr3Ca3CuyOx (y=0 to 5) and Li-doped Bi4Sr3Ca3-zLizCu4Ox (z=0.1, 0.5, and 1.0) glasses are reported. The variation of activation energy with glass compositions dominates the conductivity. Unlike many glasses with transition-metal ions, a strong preexponential factor containing the ``small-polaron'' tunneling term [exp(-2αR)] is observed. Nonadiabatic small-polaron hopping mechanism is found to be appropriate for explaining the conductivity data of both glass systems. Addition of alkali-metal ions decreases the conductivities and causes appreciable change of some model parameters obtained from least-squares fittings of the experimental data. The overall thermal behavior of the electrical conductivities of the glasses, however, remains unaltered. This indicates that small (less than 10 wt.%) amount of Li or other alkali-metal ions in these glasses acts as a flux to keep the oxygen content fixed in the corresponding glass-ceramic (superconducting) phases. This in turn helps increase the superconducting transition temperature of the glass ceramics and also lower the sintering and melting temperatures of the glasses.

  2. Resistive switching in ceramic multiferroic Bi{sub 0.9}Ca{sub 0.1}FeO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Rubi, Diego, E-mail: rubi@tandar.cnea.gov.ar [GIA and INN, CAC-CNEA, 1650 San Martin (Argentina); Gomez-Marlasca, Fernando [GIA and INN, CAC-CNEA, 1650 San Martin (Argentina); Bonville, Pierre; Colson, Dorothee; Levy, Pablo [CEA Saclay, IRAMIS, SPEC (CNRS URA 2464), F-91191 Gif sur Yvette (France)

    2012-08-15

    We report resistive switching effects in polycrystalline samples of the multiferroic Bi{sub 0.9}Ca{sub 0.1}FeO{sub 3} with silver electrodes. Moessbauer spectroscopy shows that upon Ca-doping the Fe remains in a 3+ valence state, suggesting charge compensation through the creation of large amounts of oxygen vacancies. Electrical characterization shows that the oxide/metal resistance can be switched between high and low resistance states by applying voltage pulses. This process was shown to be forming free and a strong relaxation after switching was found. We rationalize our results by considering oxygen vacancies migration to and from the metal-oxide interface, resulting in variations of the Schottky potential barrier height that modulate the interface resistance.

  3. Microstructural Control and Characterization of Bi2V0.9Cu0.1O5.35 (BICUVOX) Ceramics

    Science.gov (United States)

    Razmyar, Soheil

    2011-12-01

    The widespread commercialization of solid-oxide fuel cells (SOFCs) and solid-oxide electrolyte cells (SOECs) is primarily limited by material degradation issues related to the required high temperature operation (>800°C). Applications of stabilized zirconia based electrolytes, which are the most commonly used oxide ion conductors, have been limited to this high temperature regime due to its low oxygen ion conductivity below 800°C. Solid electrolytes made of the BIMEVOX compositional family of materials (Bi2MexV 1-xO5.5-delta where Me=Cu, Co, Mg, Ni, Fe...) exhibit high oxide ionic conductivity similar to YSZ at a low temperature (300--600°C). Among these materials copper-substituted bismuth vanadate (Bi2V0.9Cu0.1O5.35, BICUVOX), was reported to have the highest ionic conductivity at 400°C (0.02 S/cm). It's one of the most important drawbacks of using BICUVOX, as a SOFC electrolyte is the low mechanical strength, which makes it unusable for most electrolyte supported applications. This research aims at improving mechanical strength by careful control of synthesis processing and sintering processes, thus making BICUVOX a viable material option for intermediate temperature SOFC. A co-precipitation method was used to synthesize submicron BICUVOX powder. The powder was utilized to fabricate a thin (< 250 microm) BICUVOX electrolyte membrane, with 2.5 cm2 active area and high mechanical strength. The fabricated BICUVOX membranes were densified to 97% theoretical density at lower sintering temperature and shorter time (675°C/1 h), and shows fine grain size (<1.5microm) and high mechanical strength (159 MPa).

  4. Ceramic insulation for superconducting Nb{sub 3}Sn cables; Isolation ceramique pour cables supraconducteurs en Nb{sub 3}Sn

    Energy Technology Data Exchange (ETDEWEB)

    Puigsegur, A

    2005-01-15

    Nb{sub 3}Sn is the best superconductor candidate for the realization of high field magnets (>11 Tesla), its implementation remains delicate because of the great brittleness of material after the heat treatment necessary to the formation of Nb{sub 3}Sn compounds. The conventional insulation for Nb{sub 3}Sn requires to perform, after the heat treatment, a vacuum resin impregnation, which adds to the cost and raises failure risk. We have proposed an innovating ceramic insulation deposited directly on the unreacted conducting cable. After the heat treatment of the niobium tin, we obtain a coil having a mechanical cohesion, while maintaining a proper conductor positioning and a suitable electric insulation. After a rheological study, to characterize the impregnated suspension, we have shown that using this insulation in a coil manufacture process does not affect the electrical properties of the Nb{sub 3}Sn wires. A solenoid of small dimensions was tested with success in high external magnetic fields and has produced a magnetic field of 3.8 T under 740 A. (author)

  5. Transport properties of a Josephson-coupled network in a superconductive ceramic of YBa{sub 2}Cu{sub 4}O{sub 8}

    Energy Technology Data Exchange (ETDEWEB)

    Deguchi, H; Nawa, D; Hashimoto, Y; Mito, M; Takagi, S [Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550 (Japan); Hagiwara, M [Faculty of Engineering and Design, Kyoto Institute of Technology, Kyoto 606-8585 (Japan); Koyama, K, E-mail: deguchi@tobata.isc.kyutech.ac.j [Faculty of Integrated Arts and Sciences, University of Tokushima, Tokushima 770-8502 (Japan)

    2009-03-01

    Ceramic YBa{sub 2}Cu{sub 4}O{sub 8} samples composed of sub-micron size grains are considered as random Josephson-coupled networks of 0 and pi junctions, and they show successive phase transitions. The first transition occurs inside each grain at T{sub c1} and the second transition occurs among the grains at T{sub c2} (> T{sub c1}), where a negative divergence of nonlinear susceptibility is found. This critical phenomenon at T{sub c2} suggests the onset of the chiral-glass phase, as predicted by Kawamura and Li. We measured the temperature dependencies of the current-voltage characteristics of the samples and derived the linear and nonlinear resistivities. With decreases in temperature, linear resistivity decreased monotonously and remained at a finite value at temperatures less than T{sub c2}, while nonlinear resistivity diminished continuously for temperatures moving towards T{sub c2}. These results are consistent with the theoretical predictions.

  6. Superconducting electronics

    NARCIS (Netherlands)

    Rogalla, Horst

    1994-01-01

    During the last decades superconducting electronics has been the most prominent area of research for small scale applications of superconductivity. It has experienced quite a stormy development, from individual low frequency devices to devices with high integration density and pico second switching

  7. Analysis on the Bi-directional Filtration Resistances of Porous Ceramic Membrane%多孔陶瓷膜双向过滤阻力试验分析

    Institute of Scientific and Technical Information of China (English)

    吕玉正; 方涛; 师杰; 梁鹏; 梁恒国

    2013-01-01

    In order to explore the function&type of filtration resistances of porous ceramic membrane,the bi⁃directional filtering way is proposed,the effective filtration area and channel sectional area of 9⁃channel porous ceramic membrane are analyzed for the bi⁃directional filtering way,and the calculation formula for the bi⁃directional filtration resistances is established. The test results show that 1)the concentration polarization resistance Rp is the main filtration resistance under trans⁃membrane pressure 0.05-0.10 MPa and cross⁃flow velocity 1.8 m/s;2)the adsorption and deposit resistance Rd is the main one under trans⁃membrane pressure 0.10-0.25 MPa and cross⁃flow velocity 1.0-2.2 m/s;3)at trans⁃membrane pressure 0.15 MPa and cross⁃flow velocity 2.2-3.0 m/s,Rm of membrane itself is the main one;and 4)the increase of the cross⁃flow velocity can effectively delay the occurrence of concentration polarization and reduce the thickness of the sedimentary adsorption layer,thus easing the membrane pollution and extending the filtration cycle.%  为研究多孔陶瓷膜过滤阻力,提出了多孔陶瓷膜双向过滤方式,分析了9通道多孔陶瓷膜在双向过滤时的有效过滤面积和通道截面积,建立了过滤阻力关系式.试验结果表明,跨膜压差0.05~0.10 MPa、错流速度1.8 m/s时,浓差极化阻力Rp为主要过滤阻力;跨膜压差0.10~0.25 MPa、错流速度1.0~2.2 m/s时,吸附沉积阻力Rd为主要过滤阻力;跨膜压差0.15 MPa、错流速度2.2~3.0 m/s时,膜自身阻力Rm是主要过滤阻力;增大错流速度能够有效延缓浓差极化的发生,减小吸附沉积层的厚度,减轻膜污染,延长过滤周期.

  8. Thermal-mechanical Properties of Epoxy-impregnated Bi-2212/Ag Composite

    Energy Technology Data Exchange (ETDEWEB)

    Li, Pei [Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Wang, Yang [Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Godeke, Arno [Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Ye, Liyang [North Carolina State Univ., Raleigh, NC (United States); Flanagan, Gene [Muons Inc., Batavia, IL (United States); Shen, Tengming [Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)

    2014-11-26

    Knowledge of the thermal-mechanical properties of epoxy/superconductor/insulation composite is important for designing, fabricating, and operating epoxy impregnated high field superconducting magnets near their ultimate potentials. We report measurements of the modulus of elasticity, Poisson’s ratio, and the coefficient of thermal contraction of epoxy-impregnated composite made from the state-of-the-art powder-in-tube multifilamentary Ag/Bi2Sr2CaCu2Ox round wire at room temperature and cryogenic temperatures. Stress-strain curves of samples made from single-strand and Rutherford cables were tested under both monotonic and cyclic compressive loads, with single strands insulated using a thin TiO2 insulation coating and the Rutherford cable insulated with a braided ceramic sleeve.

  9. Role of valence changes and nanoscale atomic displacements in BiS2-based superconductors.

    Science.gov (United States)

    Cheng, Jie; Zhai, Huifei; Wang, Yu; Xu, Wei; Liu, Shengli; Cao, Guanghan

    2016-11-22

    Superconductivity within layered crystal structures has attracted sustained interest among condensed matter community, primarily due to their exotic superconducting properties. EuBiS2F is a newly discovered member in the BiS2-based superconducting family, which shows superconductivity at 0.3 K without extrinsic doping. With 50 at.% Ce substitution for Eu, superconductivity is enhanced with Tc increased up to 2.2 K. However, the mechanisms for the Tc enhancement have not yet been elucidated. In this study, the Ce-doping effect on the self-electron-doped superconductor EuBiS2F was investigated by X-ray absorption spectroscopy (XAS). We have established a relationship between Ce-doping and the Tc enhancement in terms of Eu valence changes and nanoscale atomic displacements. The new finding sheds light on the interplay among superconductivity, charge and local structure in BiS2-based superconductors.

  10. Role of valence changes and nanoscale atomic displacements in BiS2-based superconductors

    Science.gov (United States)

    Cheng, Jie; Zhai, Huifei; Wang, Yu; Xu, Wei; Liu, Shengli; Cao, Guanghan

    2016-11-01

    Superconductivity within layered crystal structures has attracted sustained interest among condensed matter community, primarily due to their exotic superconducting properties. EuBiS2F is a newly discovered member in the BiS2-based superconducting family, which shows superconductivity at 0.3 K without extrinsic doping. With 50 at.% Ce substitution for Eu, superconductivity is enhanced with Tc increased up to 2.2 K. However, the mechanisms for the Tc enhancement have not yet been elucidated. In this study, the Ce-doping effect on the self-electron-doped superconductor EuBiS2F was investigated by X-ray absorption spectroscopy (XAS). We have established a relationship between Ce-doping and the Tc enhancement in terms of Eu valence changes and nanoscale atomic displacements. The new finding sheds light on the interplay among superconductivity, charge and local structure in BiS2-based superconductors.

  11. Tem analyses of the local crystal and domain structures in (Na(1-x)K(x))0.5Bi(0.5)TiO3 perovskite ceramics.

    Science.gov (United States)

    Otonicar, Mojca; Skapin, Sreco D; Jancar, Bostjan

    2011-09-01

    The local crystal and domain structures of the ((Na(1-x)K(x))(0.5)Bi(0.5)TiO(3) (NBT-KBT) solid solutions were studied because of their influence on the enhanced electromechanical properties of ceramics. Based on X-ray diffraction, the morphotropic phase boundary (MPB) was determined for the composition x = 0.20, in which the rhombohedral and the tetragonal structures were observed to coexist. However, detailed domain-structure analyses using transmission electron microscopy (TEM), performed on the NBT, KBT, and five NBT-KBT solid-solution compositions, revealed some structural changes at/near the MPB. In the samples on the tetragonal side of the MPB, the grains showed a lamellar domain structure with 90° orientations of the individual domains, separated by straight domain boundaries, i.e., (011)/(101) twin planes. The rhombohedral samples on the other side of the MPB showed a typical square-net pattern with needle-like or lamellar ~71°/109° rhombohedral domains with (001) and/or (110) twin planes separating the individual domains. The domain structure at the MPB showed well-defined lamellar domains. Based on the occurrence of the superstructure reflections in the SAED patterns of various crystallographic zones, on the characteristic splitting of the reflections, and on the domain morphology observations, the crystal structure in/near the boundary region was determined to be a tetragonal structure with an in-phase oxygen octahedral tilt system (probably a(0)a(0)c(+)). It is suggested that the tetragonal polar order is partly induced from the rhombohedral structure at the MPB as a result of mechanical loading during TEM sample preparation.

  12. Phase transition, piezoelectric, and multiferroic properties of La(Co{sub 0.5}Mn{sub 0.5})O{sub 3}-modified BiFeO{sub 3}-BaTiO{sub 3} lead-free ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Lingling; Jiang, Na; Zou, Xiao; Sun, Ting; Zheng, Qiaoji; Xu, Chenggang; Lin, Dunmin [College of Chemistry and Materials Science, Sichuan Normal University, Chengdu (China); Shi, Dongliang; Lam, Kwok Ho [Department of Electrical Engineering, The Hong Kong Polytechnic University, Kowloon (China)

    2015-09-15

    (0.75-x)BiFeO{sub 3}-0.25BaTiO{sub 3}-xLa(Co{sub 0.5}Mn{sub 0.5})O{sub 3} + 1 mol% MnO{sub 2} lead-free ceramics (x = 0-0.10) were synthesized by a conventional solid-state reaction route and the effects of La(Co{sub 0.5}Mn{sub 0.5})O{sub 3} on phase transition, piezoelectric, ferroelectric, and multiferroic properties of the ceramics were investigated. The ceramics can be well sintered at 960 C for 2 h. After the addition of La(Co{sub 0.5}Mn{sub 0.5})O{sub 3}, the crystal structure of the ceramics is transformed from rhombohedral (space group R3c) to orthorhombic symmetry (space group Amm2), and the morphotropic phase boundary (MPB) of rhombohedral and orthorhombic phases is formed at x = 0.01-0.03. The dielectric peak of the ceramics was found to become diffusive with increasing x. The ceramics with x = 0-0.03 possess strong piezoelectricity with d{sub 33} of 95-108 pC N{sup -1}, strong ferroelectricity with P{sub r} of 2.2-18.1 μC cm{sup -2}, considerable magnetoelectric coefficient of 372-672 mV/cmOe, and high Curie temperature of 523-659 C, showing potential applications in multiferroic devices. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. New (1 - x)K0.45Na0.55Nb0.96Sb0.04O3-xBi0.5Na0.5HfO3 lead-free ceramics: Phase boundary and their electrical properties

    Science.gov (United States)

    Tao, Hong; Wu, Jiagang; Zheng, Ting; Wang, Xiangjian; Lou, Xiaojie

    2015-07-01

    Here, we reported a high unipolar strain and large piezoelectricity in new (1 - x)K0.45Na0.55Nb0.96Sb0.04O3-xBi0.5Na0.5HfO3 ceramics. The rhombohedral-tetragonal (R-T) phase boundary was constructed in the ceramics with 0.03 piezoelectricity of the ceramics could be effectively enhanced if their compositions are located at the phase boundaries region, where a very low electric field of ˜1.2 kV/mm can readily rotate the R/T domains. We also noticed that the deviation from phase boundary induced by applying an external electric field results in the deterioration of piezoelectricity after the "second-poling" method. We believe that as a potassium-sodium-niobate based material, the ceramics developed in this work may find practical applications in lead-free piezoelectric devices such as actuators and fuel injectors in the future owing to the significant enhancement in their piezoelectricity as well as strain.

  14. Effect of the Yb3+ Concentration in Up-Conversion and Electrical Properties of Ho3+/Yb3+ Co-doped (0.94Na0.5Bi0.5TiO3-0.06BaTiO3) Ceramics

    Science.gov (United States)

    Liu, Qian; Li, Yanxia; Li, Jun; Chai, Xiaona; Zhao, Haifeng; Wang, Xusheng; Yao, Xi

    2016-07-01

    Ho3+/Yb3+ co-doped 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 (NBT-BT:Ho3+/Yb3+) ceramics were synthesized by solid-state reaction and characterized by x-ray diffraction (XRD), luminescent, dielectric, ferroelectric and piezoelectric measurements. The XRD diffraction data showed that all the ceramics were single phase with a perovskite structure. Bright green up-conversion (UC) emission bands (545 nm) and weak red UC emission bands (660 nm) corresponded to the transitions from (5F4, 5S2) → 5I8 and 4I5 → 5I8, respectively. Furthermore, optimized UC emission intensity was observed in the NBT-BT:0.005Ho3+/0.03Yb3+ samples. The thermal behavior of UC emission in the ceramics was also investigated and the maximum sensitivity based on fluorescence intensity ratio (FIR) technology was approximately 0.0042 K-1 at 100 K. Moreover, relatively good dielectric properties ( ɛ = 4475) and ferroelectric properties ( P r = 32 μ/cm2 and E c = 37 kV) were obtained in NBT-BT:0.005Ho3+/0.005Yb3+. As a multi-functional material, NBT-BT:Ho3+/Yb3+ ceramics may be useful in electro-optical devices.

  15. 弯曲应变对Bi2223/Ag带材临界电流的影响%Effects of Bending Strain on Critical Current of Bi2223/Ag Tapes

    Institute of Scientific and Technical Information of China (English)

    李利; 谢述锋; 王德义

    2012-01-01

    Bending stress-strain characteristics and effect of bending fatigue on critical current of Bi2223/Ag tapes are investigated at 77 K under self field. The results shown that critical current /c reduction is due to the micro cracks of superconductive ceramic core caused by the bending strain and thermal cycle. Experimental study found that lc declined obviously when the bending strains of tapes was more than 0. 3% and significant decrease of /c occurred within 4 cycles and then the decrease became gentle in repeated bending test. Therefore the bending strain of Bi2223/Ag tapes should not exceed 0. 3% in application, and Bi2223/Ag tapes should be bended as few times as possible in process of production and use.%本文主要研究了Bi223/Ag带材的弯曲应力-应变特征及弯曲疲劳对其在77K自场下临界电流的影响.分析临界电流Ic降低的原因是应变和热循环引起的超导陶瓷芯内部的微裂纹.实验研究发现当带材的弯曲应变超过0.3%以后,Ic显著降低;当带材受到多次弯曲时,前四次弯曲会使Ic急剧降低,然后Ic降低非常缓慢.因此,在实际应用过程中,应使Bi223/Ag带材的弯曲应变不超过0.3%,且在Bi223/Ag带材的生产和使用过程中,均应尽量减少其弯曲的次数.

  16. Microstructure and electrical properties of pure 110K phase in the BiPbSrCaCuO system

    Science.gov (United States)

    Holguin, E.; Berger, H.; Lévy, F.; Dwir, B.; Pavuna, D.; Burri, G.

    1991-01-01

    The temperature dependence of the d.c. resistivity and a.c. magnetic susceptibility was investigated in bulk ceramics of the BiPbSrCaCuO system with 2212 - free (2223) phase. The temperature domain needed to synthesize this phase was small and, according to the actual temperature used, the superconducting properties of the samples were strongly modified. The corresponding X-ray diffraction lines of the 110K phase can be indexed in the pseudo-orthorhombic unit cell with parameters 5.40x5.41x37Å 3. SEM microprobe study revealed the presence of several non-superconducting phases and a composition 2.1:0.1:2:2:3 for the cation ratio Bi:Pb:Sr:Ca:Cu of the 110K phase. Electrical measurements (d.c. resistivity and a.c. susceptibility) confirmed the existence of a 2212 - free (2223) phase. A low temperature "tail" in the d.c. electrical resistivity marks the low value of critical current in the samples.

  17. Near-net-shape fabrication of continuous Ag-Clad Bi-Based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Lanagan, M. T. et al.

    1998-04-01

    We have developed a near-net-shape process for Ag-clad Bi-2212 superconductors as an alternative to the powder-in-tube process. This new process offers the advantages of nearly continuous processing, minimization of processing steps, reasonable ability to control the Bi-2212/Ag ratio, and early development of favorable texture of the Bi-2212 grains. Superconducting properties are discussed.

  18. On Ceramics.

    Science.gov (United States)

    School Arts, 1982

    1982-01-01

    Presents four ceramics activities for secondary-level art classes. Included are directions for primitive kiln construction and glaze making. Two ceramics design activities are described in which students make bizarrely-shaped lidded jars, feet, and footwear. (AM)

  19. Melt processing of Bi--2212 superconductors using alumina

    Science.gov (United States)

    Holesinger, Terry G.

    1999-01-01

    Superconducting articles and a method of forming them, where the superconducting phase of an article is Bi.sub.2 Sr.sub.2 CaCu.sub.2 O.sub.y (Bi-2212). Alumina is combined with Bi-2212 powder or Bi-2212 precursor powder and, in order to form an intimate mixture, the mixture is melted and rapidly cooled to form a glassy solid. The glassy solid is comminuted and the resulting powder is combined with a carrier. An alternative to melting is to form the mixture of nanophase alumina and material having a particle size of less than about 10 microns. The powder, with the carrier, is melt processed to form a superconducting article.

  20. Interaction of Au, Ag, and Bi ions with Ba2YCu3O(7-y) - Implications for superconductor applications

    Science.gov (United States)

    Hepp, A. F.; Gaier, J. R.; Pouch, J. J.; Hambourger, P. D.

    1988-01-01

    Results are presented on the reactions of Au, Ag, and Bi ions with Ba2YCu3O(7-y) oxides and on the properties of the resultant materials. The results indicate that Au(3+) structural chemistry makes gold an excellent candidate for multiphase structures of the Ba2Y(Cu/1-x/Au/x/)3O(7-y)-type substituted superconductors. Silver is structurally and chemically compatible with the perovskite structure, but when it forms a second phase, it does so without the destruction of the superconducting phase, making silver a useful metal for metal/ceramic applications. On the other hand, bismuth was shown to degrade Tc phase or to form other phases, indicating that it may not be useful in applications with rare-earth-based superconductors.

  1. Creep in electronic ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Routbort, J. L.; Goretta, K. C.; Arellano-Lopez, A. R.

    2000-04-27

    High-temperature creep measurements combined with microstructural investigations can be used to elucidate deformation mechanisms that can be related to the diffusion kinetics and defect chemistry of the minority species. This paper will review the theoretical basis for this correlation and illustrate it with examples from some important electronic ceramics having a perovskite structure. Recent results on BaTiO{sub 3}, (La{sub 1{minus}x}Sr){sub 1{minus}y}MnO{sub 3+{delta}}, YBa{sub 2}Cu{sub 3}O{sub x}, Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x}, (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} and Sr(Fe,Co){sub 1.5}O{sub x} will be presented.

  2. Impedance and modulus spectroscopy characterization of Tb modified Bi{sub 0.8}A{sub 0.1}Pb{sub 0.1}Fe{sub 0.9}Ti{sub 0.1}O{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Thakur, Shweta; Rai, Radheshyam, E-mail: rshyam1273@gmail.com [School of Physics, Shoolini University, Himachal Pradesh (India); Bdikin, Igor [Centre for Mechanical Technology and Automation (TEMA), University of Aveiro (Portugal); Valente, Manuel Almeida [Departamento de Fisica, Universidade de Aveiro (Portugal)

    2016-01-15

    In this paper we present the impedance spectroscopy of ternary solid solutions of BiFeO{sub 3} , TbFeO{sub 3} and PbTiO{sub 3} , prepared by solid-state reaction method. The preliminary structural studies were carried out by X-ray diffraction technique, showing the formation of polycrystalline sample with ABO{sub 3} type of perovskite structure with hexagonal symmetry for Bi{sub 0.8}Tb{sub 0.1}Pb{sub 0.1}Fe{sub 0.9}Ti{sub 0.1}O{sub 3} system at room temperature. Dielectric and impedance study of this ceramic has been characterized in the temperature range 175 - 325 deg C and frequency range 100 Hz - 1 MHz. The maximum ferroelectric transition temperature (T{sub c} ) of this system was in the range 210 - 225 deg C with the dielectric constant having maximum value ∼ 2480 at 1 kHz. The complex impedance graph exhibited one impedance semicircle arc at all reported temperatures, which indicates that the impedance response is a Cole-Cole type relaxation. Single semicircle indicate that the grain effect of the bulk in ceramic. The bulk resistance of the material decreases with increasing temperature showing negative temperature showing a typical semiconducting property, i.e. negative temperature coefficient of resistance (NTCR) behavior. (author)

  3. The effect of K-na co-doping on the formation and particle size of Bi-2212 phase

    Energy Technology Data Exchange (ETDEWEB)

    Kır, M. Ebru [Department of Physics, Faculty of Arts and Sciences, Mersin University, Çiftlikköy, 33343 Mersin (Turkey); Özkurt, Berdan, E-mail: berdanozkurt@mersin.edu.tr [Department of Physics, Faculty of Arts and Sciences, Mersin University, Çiftlikköy, 33343 Mersin (Turkey); Department of Energy Systems Engineering, Faculty of Tarsus Technology, Mersin University, Mersin (Turkey); Advanced Technology Research and Application Center, Mersin University, Yenişehir, TR-33343 Mersin (Turkey); Aytekin, M. Ersin [Advanced Technology Research and Application Center, Mersin University, Yenişehir, TR-33343 Mersin (Turkey)

    2016-06-01

    Superconducting K-Na co-doped Bi{sub 2}Sr{sub 2}K{sub x}Ca{sub 1}Cu{sub 1.75}Na{sub 0.25}O{sub y} (x=0, 0.05, 0.1 and 0.25) ceramics are prepared by a solid-state reaction method. It is clearly determined from XRD data that the characteristic peaks of Bi-2212 phase are observed in all samples. The resistivity measurements show that T{sub c} (onset) values is gradually increasing as K content is increased. It is also found that K-Na co-doping influence the grain sizes for Bi-2212 phase significantly. The critical current densities as a function of magnetic field have been calculated from M–H hysteresis loops of samples according to Bean's critical model, indicating that K-Na co-doping cause higher J{sub c} values than the pure ones.

  4. Superconducting Microelectronics.

    Science.gov (United States)

    Henry, Richard W.

    1984-01-01

    Discusses superconducting microelectronics based on the Josephson effect and its advantages over conventional integrated circuits in speed and sensitivity. Considers present uses in standards laboratories (voltage) and in measuring weak magnetic fields. Also considers future applications in superfast computer circuitry using Superconducting…

  5. Ceramic Processing

    Energy Technology Data Exchange (ETDEWEB)

    EWSUK,KEVIN G.

    1999-11-24

    Ceramics represent a unique class of materials that are distinguished from common metals and plastics by their: (1) high hardness, stiffness, and good wear properties (i.e., abrasion resistance); (2) ability to withstand high temperatures (i.e., refractoriness); (3) chemical durability; and (4) electrical properties that allow them to be electrical insulators, semiconductors, or ionic conductors. Ceramics can be broken down into two general categories, traditional and advanced ceramics. Traditional ceramics include common household products such as clay pots, tiles, pipe, and bricks, porcelain china, sinks, and electrical insulators, and thermally insulating refractory bricks for ovens and fireplaces. Advanced ceramics, also referred to as ''high-tech'' ceramics, include products such as spark plug bodies, piston rings, catalyst supports, and water pump seals for automobiles, thermally insulating tiles for the space shuttle, sodium vapor lamp tubes in streetlights, and the capacitors, resistors, transducers, and varistors in the solid-state electronics we use daily. The major differences between traditional and advanced ceramics are in the processing tolerances and cost. Traditional ceramics are manufactured with inexpensive raw materials, are relatively tolerant of minor process deviations, and are relatively inexpensive. Advanced ceramics are typically made with more refined raw materials and processing to optimize a given property or combination of properties (e.g., mechanical, electrical, dielectric, optical, thermal, physical, and/or magnetic) for a given application. Advanced ceramics generally have improved performance and reliability over traditional ceramics, but are typically more expensive. Additionally, advanced ceramics are typically more sensitive to the chemical and physical defects present in the starting raw materials, or those that are introduced during manufacturing.

  6. Ceramic joining

    Energy Technology Data Exchange (ETDEWEB)

    Loehman, R.E. [Sandia National Lab., Albuquerque, NM (United States)

    1996-04-01

    This paper describes the relation between reactions at ceramic-metal interfaces and the development of strong interfacial bonds in ceramic joining. Studies on a number of systems are described, including silicon nitrides, aluminium nitrides, mullite, and aluminium oxides. Joints can be weakened by stresses such as thermal expansion mismatch. Ceramic joining is used in a variety of applications such as solid oxide fuel cells.

  7. Growth of superconducting Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} films by sedimentation deposition and liquid phase sintering and annealing technique

    Energy Technology Data Exchange (ETDEWEB)

    Manahan, R.L.C. [Condensed Matter Physics Laboratory, National Institute of Physics, University of the Philippines, Llamas Science Hall, Rm. 3122, E. Quirino Street, Diliman, Quezon City 1101 (Philippines)]. E-mail: rcmanahan@nip.upd.edu.ph; Sarmago, R.V. [Condensed Matter Physics Laboratory, National Institute of Physics, University of the Philippines, Llamas Science Hall, Rm. 3122, E. Quirino Street, Diliman, Quezon City 1101 (Philippines)

    2006-10-01

    We report on a technique of growing highly c-axis oriented Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} (Bi-2212) thick films on MgO substrate using a combined sedimentation-deposition and liquid phase sintering and annealing process. The temperature profiles employed partial melting followed by rapid cooling to temperature below the melting point. Scanning electron micrographs show that the films have a smooth surface. No evidence of grain boundaries on the film's surface can be seen. The critical temperatures of the samples range from {approx}67 K to {approx}81 K. This method presents a quick and easy preparation for high quality epitaxial Bi-2212 films.

  8. Microstructure and properties of Bi-2223/Ag/Ni tapes

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    To reduce the production cost of Bi-2223 superconducting tapes, Bi-2223/Ag/Ni tapes were fabricated by the powder-in-tube process. The effect of heat treatment on the microstructure and critical current of the Bi-2223/Ag/Ni tapes were studied. The phase compositions of the samples were characterized using XRD. The microstructure was observed using SEM. Experimental results indicate that higher temperature is more conducive to the formation of Bi-2223 phase at an atmosphere of 8.5% O 2 . After the two-step h...

  9. Diffused phase transition in fine-grained bismuth vanadate ceramics

    OpenAIRE

    Shantha, K; Varma, KBR

    1999-01-01

    Nanocrystalline powders of ferroelectric bismuth vanadate, Bi4V2O11 (n-BiV), with crystallite size less than 50 nm, were obtained by mechanical milling of a stoichiometric mixture of bismuth oxide and vanadium pentoxide. The n-BiV powders on sintering yielded high-density, fine-grained ceramics with improved dielectric and polar characteristics. Dielectric studies on samples obtained from milled powders indicated that the ferroelectric-to-paraelectric phase transition temperature is strongly ...

  10. Structure and properties of (1−x)[(K$_{0.5}$Na$_{0.5}$)NbO$_3$–LiSbO$_3$]– xBiFe$_{0.8}$Co$_{0.2}$O$_3$ lead-free piezoelectric ceramics

    Indian Academy of Sciences (India)

    HUA WANG; XIAYAN ZHAO; JIWEN XU; XIA ZHAI; LING YANG

    2016-06-01

    Lead-free piezoelectric ceramics $(1−x)$[0.95(K$_{0.5}$Na$_{0.5}$)NbO$_3$–0.05LiSbO$_3$]–$x$BiFe$_{0.8}$Co$_{0.2}$O$_{3}$(KNN–LS–$x$BFC) were prepared by a conventional sintering technique. The effect of BFC content on the structure, piezoelectricand electrical properties of KNN–LS ceramics was investigated. The results reveal that the BFC is effective in promoting the sinterability and the electrical properties of the ceramics sintering at low temperature of 1030$^{\\circ}$C. Theceramics show a single perovskite structure, in which the tetragonal phase decreases while the orthorhombic phase increases with the increase of $x$. The more the BFC content is, the smaller and homogeneous grains were formed.With the increase of $x$, the $d_{33}$ and the $k_p$ increase to a maximum value and then slightly decrease, but the $Q_m$ increases continuously. As BFC content increases, the Curie temperature $T_c$ and remnant polarization $P_r$ decrease, but the diffusivity of phase transition in KNN–LS ceramics will intensify and the coercive field $E_c$ fluctuate between 1.16 and 1.51 kV mm$^{−1}$. The samples with $x =0.004$ exhibit optimum electrical properties at room temperature ($d_{33} = 268 pC$ N$^{−1}$, $k_p =52$%, $\\epsilon_r = 1366$, $\\tan \\delta =2.11$%, $T_c = 325^{\\circ}$C, $P_r = 20.4$ $\\mu$C cm$^{−2}$, $E_c =1.16$ kV mm$^{−1}$).

  11. Color superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Wilczek, F. [Institute for Advanced Study, Princeton, NJ (United States)

    1997-09-22

    The asymptotic freedom of QCD suggests that at high density - where one forms a Fermi surface at very high momenta - weak coupling methods apply. These methods suggest that chiral symmetry is restored and that an instability toward color triplet condensation (color superconductivity) sets in. Here I attempt, using variational methods, to estimate these effects more precisely. Highlights include demonstration of a negative pressure in the uniform density chiral broken phase for any non-zero condensation, which we take as evidence for the philosophy of the MIT bag model; and demonstration that the color gap is substantial - several tens of MeV - even at modest densities. Since the superconductivity is in a pseudoscalar channel, parity is spontaneously broken.

  12. Influence of gold diffusion-doped on phase formation, superconducting and microstructure properties of Bi{sub 1.8}Pb{sub 0.35}Sr{sub 1.9}Ca{sub 2.1}Cu{sub 3}O{sub y} superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Ozturk, O [Department of Physics, Faculty of Arts and Sciences, Kastamonu University, 37600 Kastamonu (Turkey); Akdogan, M; Terzioglu, C [Department of Physics, Faculty of Arts and Sciences, Abant Izzet Baysal University, 14280 Bolu (Turkey); Gencer, A, E-mail: terzioglu_c@ibu.edu.t [Department of Physics, Faculty of Arts and Sciences, Ankara University, 06100 Ankara (Turkey)

    2009-03-01

    We report on low-field magnetic properties of gold diffusion-doped Bi{sub 1.8}Pb{sub 0.35}Sr{sub 1.9}Ca{sub 2.1}Cu{sub 3}O{sub y} superconducting bulk samples by performing ac susceptibility measurements. The undoped samples were prepared by the standard solid-state reaction method. Doping of Bi{sub 1.8}Pb{sub 0.35}Sr{sub 1.9}Ca{sub 2.1}Cu{sub 3}O{sub y} was carried out by means of Au-diffusion during sintering from an evaporated gold film on pellets. To investigate the effect of gold-diffusion and diffusion-annealing duration on transport, magnetic and microstructure properties of the superconducting samples we performed magnetoresistivity, scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements. The ac susceptibility as a function of temperature measurements were carried out at different values of the ac magnetic field amplitudes (Hac) in the range between 20A/m and 320 A/m for 211 Hz. The imaginary part of ac susceptibility measurements is used to calculate intergranular critical current density J{sub c}(T{sub p}) using the Bean Model. J{sub c}(T{sub p}) is seen to increase from 60 A cm{sup -2} to 90 A cm{sup -2} with increasing diffusion-annealing time from 10 h to 50 h. The peak temperature, T{sub p}, in the imaginary part of the ac susceptibility is shifted to a lower temperature with decreasing diffusion-annealing duration as well as increasing ac magnetic fields. The force pinning density (alpha{sub j}j (0)) increased with increasing diffusion annealing time. The value of T{sub c} in gold-diffused samples, in comparison with the undoped samples, increased from 100 +- 0.2 K to 104 +- 0.2 K. It was observed that the value of T{sub c-offset} of the gold-doped samples enhanced with further increasing diffusion-annealing duration. XRD patterns and SEM micrographs are used to obtain information about Bi-2223 phase ratio, lattice parameters and grain size of the samples. Gold doping enhanced the formation high-T{sub c} phase and increased the

  13. SUPERCONDUCTING PHOTOCATHODES.

    Energy Technology Data Exchange (ETDEWEB)

    SMEDLEY, J.; RAO, T.; WARREN, J.; SEKUTOWICZ, LANGNER, J.; STRZYZEWSKI, P.; LEFFERS, R.; LIPSKI, A.

    2005-10-09

    We present the results of our investigation of lead and niobium as suitable photocathode materials for superconducting RF injectors. Quantum efficiencies (QE) have been measured for a range of incident photon energies and a variety of cathode preparation methods, including various lead plating techniques on a niobium substrate. The effects of operating at ambient and cryogenic temperatures and different vacuum levels on the cathode QE have also been studied.

  14. Growth of layered superconductor β-PdBi2 films using molecular beam epitaxy

    Science.gov (United States)

    Denisov, N. V.; Matetskiy, A. V.; Tupkalo, A. V.; Zotov, A. V.; Saranin, A. A.

    2017-04-01

    Bulk β-PdBi2 layered material exhibits advanced properties and is supposed to be probable topological superconductor. We present a method based on molecular beam epitaxy that allows us to grow β-PdBi2 films from a single β-PdBi2 triple layer up to the dozens of triple layers, using Bi(111) film on Si(111) as a template. The grown films demonstrate structural, electronic and superconducting properties similar to those of bulk β-PdBi2 crystals. Ability to grow the β-PdBi2 films of desired thickness opens the promising possibilities to explore fascinating properties of this advanced material.

  15. Superconductivity and structural characteristics of ceramic Pr{sub 2}Ba{sub 4}Cu{sub 7}O{sub 15-{delta}} prepared by ambient pressure synthesis using citrate pyrolysis method

    Energy Technology Data Exchange (ETDEWEB)

    Hagiwara, M. [Department of Comprehensive Sciences, Kyoto Institute of Technology, Sakyo-ku, Kyoto 606-8585 (Japan)], E-mail: hag@kit.ac.jp; Shima, T.; Tanaka, S.; Nishio, K.; Isshiki, T. [Department of Comprehensive Sciences, Kyoto Institute of Technology, Sakyo-ku, Kyoto 606-8585 (Japan); Saito, T.; Koyama, K. [University of Tokushima, Tokushima 770-8502 (Japan)

    2007-10-01

    Sintered material of Pr{sub 2}Ba{sub 4}Cu{sub 7}O{sub 15-{delta}} (Pr247) was synthesized at ambient pressure condition by using citrate pyrolysis precursor method, and the superconductivity caused by oxygen reduction treatment has been confirmingly observed and examined. By resistivity and magnetization experiments, it has been found that the critical temperature T{sub c} of the reduced samples could reach about 10 K higher than previously reported data for pure Pr247. Besides, from TEM observations, the present material was found to be heterogeneous system containing Pr247, Pr124 and novel stacking structure phases rich in CuO single chains. These results have suggested that oxygen-reduction at such region rich in the CuO single chains may affect the superconductivity of the adjacent crystal region containing CuO double chains, and might enhance the superconductive critical temperature.

  16. Superconductivity in Cuba: Reaching the Frontline

    Science.gov (United States)

    Arés Muzio, Oscar; Altshuler, Ernesto

    The start of experimental research in the field of superconductivity was a very special moment for Cuban physics: Cuban scientists at the Physics Faculty, University of Havana, synthesized the first Cuban superconductor (a 123-YBCO ceramic sample) just 2 months after the publication of the famous paper by Wu and co-workers that triggered the frantic race of High Tc superconductors all over the world. We timely joined the world's frontline in superconductor research.

  17. Ceramic Methyltrioxorhenium

    CERN Document Server

    Herrmann, R; Eickerling, G; Helbig, C; Hauf, C; Miller, R; Mayr, F; Krug von Nidda, H A; Scheidt, E W; Scherer, W; Herrmann, Rudolf; Troester, Klaus; Eickerling, Georg; Helbig, Christian; Hauf, Christoph; Miller, Robert; Mayr, Franz; Nidda, Hans-Albrecht Krug von; Scheidt, Ernst-Wilhelm; Scherer, Wolfgang

    2006-01-01

    The metal oxide polymeric methyltrioxorhenium [(CH3)xReO3] is an unique epresentative of a layered inherent conducting organometallic polymer which adopts the structural motifs of classical perovskites in two dimensions (2D) in form of methyl-deficient, corner-sharing ReO5(CH3) octahedra. In order to improve the characteristics of polymeric methyltrioxorhenium with respect to its physical properties and potential usage as an inherentconducting polymer we tried to optimise the synthetic routes of polymeric modifications of 1 to obtain a sintered ceramic material, denoted ceramic MTO. Ceramic MTO formed in a solvent-free synthesis via auto-polymerisation and subsequent sintering processing displays clearly different mechanical and physical properties from polymeric MTO synthesised in aqueous solution. Ceramic MTO is shown to display activated Re-C and Re=O bonds relative to MTO. These electronic and structural characteristics of ceramic MTO are also reflected by a different chemical reactivity compared with its...

  18. Pb solubility of the high-temperature superconducting phase Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+d}

    Energy Technology Data Exchange (ETDEWEB)

    Kaesche, S.; Majewski, P.; Aldinger, F. [Max-Planck-Institut fuer Metallforschung, Stuttgart (Germany)] [and others

    1994-12-31

    For the nominal composition of Bi{sub 2.27x}Pb{sub x}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+d} the lead content was varied from x=0.05 to 0.45. The compositions were examined between 830{degrees}C and 890{degrees}C which is supposed to be the temperature range over which the so-called 2223 phase (Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+d}) is stable. Only compositions between x=0.18 to 0.36 could be synthesized in a single phase state. For x>0.36 a lead containing phase with a stoichiometry of Pb{sub 4}(Sr,Ca){sub 5}CuO{sub d} is formed, for x<0.18 mainly Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+d} and cuprates are the equilibrium phases. The temperature range for the 2223 phase was found to be 830{degrees}C to 890{degrees}C but the 2223 phase has extremely varying cation ratios over this temperature range. Former single phase 2223 samples turn to multi phase samples when annealed at slightly higher or lower temperatures. A decrease in the Pb solubility with increasing temperature was found for the 2223 phase.

  19. Stratification of the Bi-Sr-Ca-Cu-O system melted under high gravity conditions

    Science.gov (United States)

    Volkov, M. P.; Melekh, B. T.; Parfen'ev, R. V.; Kartenko, N. F.; Turchaninov, A. M.; Regel, L. L.

    1992-08-01

    The structure and magnetic properties of high Tc superconductor Bi-Sr-Ca-Cu-O samples remelted under gravity levels have been investigated. Superconducting properties make a change along the ingots. The dependence of structural and superconducting properties on the gravity level and their time degradation have been observed.

  20. Transport properties of YBaCuO and BiSrCaCuO thin films in the thermodynamic fluctuation range

    Energy Technology Data Exchange (ETDEWEB)

    Lang, W. (Ludwig Boltzmann Inst. fuer Festkoerperphysik, Wien (Austria)); Heine, G. (Ludwig Boltzmann Inst. fuer Festkoerperphysik, Wien (Austria)); Sekirnjak, C. (Ludwig Boltzmann Inst. fuer Festkoerperphysik, Wien (Austria)); Schwab, P. (Inst. fuer Angewandte Physik, Univ. Linz (Austria)); Wang, X.Z. (Inst. fuer Angewandte Physik, Univ. Linz (Austria)); Baeuerle, D. (Inst. fuer Angewandte Physik, Univ. Linz (Austria)); Kula, W. (Dept. of Electrical Engineering and Lab. for Laser Energetics, Univ. of Rochester, NY (United States) Inst. of Physics, Polish Academy of Sciences, Warszawa (Poland)); Sobolewski, R. (Dept. of Electrical Engineering and Lab. for Laser Energetics, Univ. of Rochester, NY (United States) Inst. of Physics, Polish Academy of Sciences, Warszawa (Poland))

    1993-04-20

    Thin films of YBaCuO have been fabricated by pulsed-laser deposition in oxygen atmosphere on MgO substrates. Films of the 2223-phase of BiSrCaCuO, stabilized by Pb-addition in the ceramic targets, were prepared by DC-magnetron sputtering. The effect of thermodynamic fluctuations of the superconducting order parameter on the normal state transport properties was investigated by measurements of the electrical resistivity, the magnetoresistance and the Hall effect. Analyzing the results in terms of Aslamazov-Larkin and Maki-Thompson theories and their extensions for 2-dimensional, layered superconductors, we obtain a consistent set of parameters from which the c-axis coherence lengths [xi][sub c](0)=1.5 A in YBaCuO and [xi][sub c](0)=1.7 A in 2223-(Bi,Pb)SrCaCuO are deduced. A significant contribution from the Maki-Thompson process was found in YBaCuO, but not such effects in the (Bi,Pb)SrCaCuO films. (orig.)

  1. Temperature dependent piezoelectric response and strain-electric-field hysteresis of rare-earth modified bismuth ferrite ceramics

    DEFF Research Database (Denmark)

    Walker, Julian; Ursic, Hana; Bencan, Andreja

    2016-01-01

    electron microscopy and piezoresponse force microscopy is coupled with a high electric-field cycling study and in situ converse d33 measurements up to 325 °C for three RE-BFO ceramic compositions, Bi0.86Sm0.14FeO3, Bi0.88Gd0.12FeO3 and Bi0.91Dy0.09FeO3. The ceramics exhibit different phase assemblages...

  2. New modulation structures observed in Bi2.13Sr1.87CuO6+δ superconductors

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    A new two-dimensional structure modulation along c-and b-axes has been discovered in superconducting single crystals of Bi2.13Sr1.87CuO6+δ(Bi2201)by x-ray scattering.Such modulation structure does not exist in non-superconducting Bi2201 single crystals.But instead lattice distortions are observed in the a-b-plane.This phenomenon may indicate that both strain relaxation and charge modulation in the a-b-plane are important to the occurrence of superconductivity in the copper oxides.

  3. Improved Piezoelectricity in (K0.44Na0.52Li0.04) (Nb0.91Ta0.05Sb0.04)O3- xBi0.25Na0.25NbO3 Lead-Free Piezoelectric Ceramics

    Science.gov (United States)

    Zhao, Yan; Xu, Zhijun; Li, Huaiyong; Hao, Jigong; Du, Juan; Chu, Ruiqing; Wei, Dongdong; Li, Guorong

    2017-01-01

    (1 - x)[(K0.44Na0.52Li0.04)(Nb0.91Ta0.05Sb0.04)O3]- xBi0.25Na0.25NbO3 (KNLNTS- xBNN) lead-free piezoelectric ceramics have been prepared using a conventional solid-state reaction method and the effects of BNN on their phase structure, microstructure, and electrical properties systematically studied. X-ray diffraction analysis suggested that BNN substitution into KNLNTS induced coexistence of orthorhombic-tetragonal mixed phase and thus improved the ferroelectric and piezoelectric properties. The surface morphologies indicated that different amounts of BNN had two different effects on grain growth. Good electrical properties ( d 33 = 256 pC N-1, T c = 354.27°C, k p = 43.43%, P r = 26.85 μC cm-2, E c = 24.47 kV cm-1) were simultaneously obtained at x = 0.0025, suggesting that our research could benefit development of (K,Na)NbO3-based ceramics and widen their application range.

  4. Structural properties of CaTi 1-x(Nb 2/3Li 2/3) xO 3-δ (CNLTO) and CaTi 1-x(Nb 1/2Ln 1/2) xO 3 (Ln=Fe (CNFTO), Bi (CNBTO)), modified dielectric ceramics for microwave applications

    Science.gov (United States)

    Costa, R. C. S.; Bruno Costa, A. D. S.; Freire, F. N. A.; Santos, M. R. P.; Almeida, J. S.; Sohn, R. S. T. M.; Sasaki, J. M.; Sombra, A. S. B.

    2009-05-01

    This paper presents an investigation of the structural characteristics of Nb 1/2Bi 1/2 (CNBTO), Nb 1/2Fe 1/2 (CNFTO) and Nb 2/3Li 1/3 (CNLTO) substitution into the B-site of calcium titanate ceramics. The modified CaTiO 3 (CTO) ceramics were prepared by the conventional solid-state method. The compounds were investigated, by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDXS). The X-ray analysis shows that all samples have an orthorhombic structure. The refinement analysis of all samples were also performed and discussed in this paper. For all studied samples, a Raman mode at 805 cm -1 was detected and its intensity increases as the substitution increases. The dielectric permittivity and loss at microwave frequencies (MW) were investigated. The CNLTO phase, present the highest dielectric constant ( k=35.8) at 3.9 GHz with loss (tg α=7×10 -3). The lowest value of k=25.7 ( f=4.8 GHz) and tg α=3×10 -3, was obtained for the CNFTO phase. These measurements confirm the possible use of such material for microwave devices like dielectric resonator antennas.

  5. Angle - resolved - photoemission study of Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8+. delta. : Metallicity of the Bi-O plane

    Energy Technology Data Exchange (ETDEWEB)

    Wells, B.O.; Shen, Z.; Dessau, D.S.; Spicer, W.E.; Olson, C.G.; Mitzi, D.B.; Kapitulnik, A.; List, R.S.; Arko, A. (Stanford Electronics Laboratories, Stanford University, Stanford, CA (USA) Ames Laboratory, Iowa State University, Ames, IA Department of Applied Physics, Stanford University, Stanford, CA (USA) Los Alamos National Laboratory, Los Alamos, NM (USA))

    1990-12-10

    We have performed high-resolution angle-resolved-photoemission experiments on Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} single crystals with different annealing histories. By depositing a small amount of Au on the surface, we were able to distinguish electronic states associated with the Bi-O surface layer. We found that the Bi-O atomic surface layer is metallic and superconducting for samples that were high-temperature annealed in oxygen but not for as-grown samples. The Cu-O plane is found to be superconducting in all samples.

  6. Engineering ceramics

    CERN Document Server

    Bengisu, Murat

    2001-01-01

    This is a comprehensive book applying especially to junior and senior engineering students pursuing Materials Science/ Engineering, Ceramic Engineering and Mechanical Engineering degrees. It is also a reference book for other disciplines such as Chemical Engineering, Biomedical Engineering, Nuclear Engineering and Environmental Engineering. Important properties of most engineering ceramics are given in detailed tables. Many current and possible applications of engineering ceramics are described, which can be used as a guide for materials selection and for potential future research. While covering all relevant information regarding raw materials, processing properties, characterization and applications of engineering ceramics, the book also summarizes most recent innovations and developments in this field as a result of extensive literature search.

  7. Effect of doping in the Bi-Sr-Ca-Cu-O superconductor

    Science.gov (United States)

    Akbar, S. A.; Wong, M. S.; Botelho, M. J.; Sung, Y. M.; Alauddin, M.; Drummer, C. E.; Fair, M. J.

    1991-01-01

    The results of the effect of doping on the superconducting transition in the Bi-Sr-Ca-Cu-O system are reported. Samples were prepared under identical conditions with varying types (Pb, Sb, Sn, Nb) and amounts of dopants. All samples consisted of multiple phases, and showed stable and reproducible superconducting transitions. Stabilization of the well known 110 K phase depends on both the type and amount of dopant. No trace of superconducting phase of 150 K and above was observed.

  8. Structural, ferroelectric and magnetic study of lead free (Na{sub 0.5}Bi{sub 0.5}){sub 1-x}La{sub x}Ti{sub 0.988}Fe{sub 0.012}O{sub 3} (x=0,0.01,0.03,0.05) ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Parmar, Kusum, E-mail: prmrkusum@gmail.com; Sharma, Anshu; Sharma, Hakikat; Negi, N. S. [Department of Physics, Himachal Pradesh University, Shimla-171005 (India)

    2015-05-15

    Lead free (Na{sub 0.5}Bi{sub 0.5}){sub 1-x}La{sub x}Ti{sub 0.988}Fe{sub 0.012}O{sub 3} ceramic having compositions (x=0, 0.01, 0.03, 0.05) has been prepared by sol gel method using citric acid. Structural analysis has been done by X-ray diffraction and FTIR measurements. XRD patterns have been confirmed perovskite structure for all samples. FTIR absorption band at around ∼630 cm{sup −1} is observed for all samples which confirm perovskite phase formation in samples. With increasing La concentration, shifting in XRD peaks and FTIR absorption bands is observed which suggests incorporation of La on A-site in prepared (Na{sub 0.5}Bi{sub 0.5}){sub 1-x}La{sub x}Ti{sub 0.988}Fe{sub 0.012}O{sub 3} samples. Effect of La substitution on Ferroelectric (Polarization vs. Electric field) and Magnetic (Magnetization vs. Magnetic field) properties have been studied at room temperature. All samples exhibit weak ferromagnetic order and also possess ferroelectric behavior which provides new insight to lead free single phase multiferroic materials.

  9. Itinerant Ferromagnetism and Superconductivity

    OpenAIRE

    Karchev, Naoum

    2004-01-01

    Superconductivity has again become a challenge following the discovery of unconventional superconductivity. Resistance-free currents have been observed in heavy-fermion materials, organic conductors and copper oxides. The discovery of superconductivity in a single crystal of $UGe_2$, $ZrZn_2$ and $URhGe$ revived the interest in the coexistence of superconductivity and ferromagnetism. The experiments indicate that: i)The superconductivity is confined to the ferromagnetic phase. ii)The ferromag...

  10. 100 years of superconductivity

    CERN Document Server

    Rogalla, Horst

    2011-01-01

    Even a hundred years after its discovery, superconductivity continues to bring us new surprises, from superconducting magnets used in MRI to quantum detectors in electronics. 100 Years of Superconductivity presents a comprehensive collection of topics on nearly all the subdisciplines of superconductivity. Tracing the historical developments in superconductivity, the book includes contributions from many pioneers who are responsible for important steps forward in the field.The text first discusses interesting stories of the discovery and gradual progress of theory and experimentation. Emphasizi

  11. Gap Filling Ceramic Insulating Putty for High Field Magnets

    Science.gov (United States)

    Rice, J. A.; Rice, H. M.

    2008-03-01

    Gaps between the A15 superconducting cable and its supports can sometimes occur requiring expensive rework of the support or filling with a non-optimal material. Recently, a new ceramic putty has been developed that can fill these gaps to fully support the superconducting cable. This ceramic material can withstand the extreme temperature differences between the high temperature heat treatment and the cryogenic operation. Significant performance improvements have been made that will enable the insulating putty to be used in some accelerator magnet systems. Processing methods will be discussed as well as strength and thermal data.

  12. Structural Ceramics Database

    Science.gov (United States)

    SRD 30 NIST Structural Ceramics Database (Web, free access)   The NIST Structural Ceramics Database (WebSCD) provides evaluated materials property data for a wide range of advanced ceramics known variously as structural ceramics, engineering ceramics, and fine ceramics.

  13. Influence of BiFeTaO{sub 3} addition on the electrical properties of Na{sub 0.4725}K{sub 0.4725}Li{sub 0.055}NbO{sub 3} ceramics system using impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kumari, Poonam [School of Physics, Shoolini University, Solan, HP (India); Rai, Radheshyam, E-mail: rshyam1273@gmail.com [School of Physics, Shoolini University, Solan, HP (India); Kholkin, A.L. [Department of Glass and Ceramics, Aveiro University, Aveiro (Portugal)

    2015-07-15

    Highlights: • (1 − x)(Na{sub 0.4725}K{sub 0.4725}Li{sub 0.055}NbO{sub 3}) − x(BiFe{sub 0.5}Ta{sub 0.5}O{sub 3}) ceramic samples have monoclinic phase. • Ferroelectric transition temperature (T{sub c}) of this system was 400–405 °C. • Dielectric properties were observed in (1 − x)(Na{sub 0.4725}K{sub 0.4725}Li{sub 0.055}NbO{sub 3}) − x(BiFe{sub 0.5}Ta{sub 0.5}O{sub 3}) system. • Activation energy increases with for concentration ratio. - Abstract: Polycrystalline samples of (1 − x)(Na{sub 0.4725}K{sub 0.4725}Li{sub 0.055}NbO{sub 3}) − x(BiFe{sub 0.5}Ta{sub 0.5}O{sub 3}) (where x = 0.005 and 0.007 were prepared by using a solid state reaction technique. The XRD patterns of the samples at room temperature shows perovskite phase with monoclinic structure. The dielectric constant for x = 0.007 is maximum. Detailed studies of dielectric and impedance properties of the materials in a wide range of frequency (100 Hz–1 MHz) and temperatures (RT–500 °C) shows that dielectric properties were strongly temperature and frequency dependent. Dielectric and electrical properties of samples, indicate that the Curie temperature shifted to higher temperature side with the increase in frequency. The AC conductivity also increases with increase in frequency. The low value of activation energy obtained for the ceramic samples could be attributed to the influence of electronic contribution to the conductivity. The plots of Z″ and M″ vs frequency at various temperatures shows peaks in the higher temperature range (>320 °C). The compounds show dielectric relaxation, which is found to be of non-Debye type and the relaxation frequency shifted to higher side with increase in temperature. The Nyquist plot and conductivity studies showed the NTCR character of samples.

  14. Ancient Technologies: The Egyptian Sintered-Quartz Ceramics

    OpenAIRE

    Sparavigna, Amelia Carolina

    2014-01-01

    To physicists and engineers, ceramics represent materials demonstrating excellent strength and hardness, materials that can serve as electrical insulators or conductors, some of them being able of a high-temperature superconductivity. To researchers working in archaeology and art history, ceramics mean objects such as figurines, tiles and tableware helping understanding cultures and technologies of the past. They are among the most common artifacts to be found in archaeological sites, because...

  15. Electrical conductivity and thermopower of (1 - x) BiFeO(3) - xBi(0.5)K(0.5)TiO3 (x = 0.1, 0.2) ceramics near the ferroelectric to paraelectric phase transition.

    Science.gov (United States)

    Wefring, E T; Einarsrud, M-A; Grande, T

    2015-04-14

    Ferroelectric BiFeO3 has attractive properties such as high strain and polarization, but a wide range of applications of bulk BiFeO3 are hindered due to high leakage currents and a high coercive electric field. Here, we report on the thermal behaviour of the electrical conductivity and thermopower of BiFeO3 substituted with 10 and 20 mol% Bi0.5K0.5TiO3. A change from p-type to n-type conductivity in these semi-conducting materials was demonstrated by the change in the sign of the Seebeck coefficient and the change in the slope of the isothermal conductivity versus partial pressure of O. A minimum in the isothermal conductivity was observed at ∼10(-2) bar O2 partial pressure for both solid solutions. The strong dependence of the conductivity on the partial pressure of O2 was rationalized by a point defect model describing qualitatively the conductivity involving oxidation/reduction of Fe(3+), the dominating oxidation state of Fe in stoichiometric BiFeO3. The ferroelectric to paraelectric phase transition of 80 and 90 mol% BiFeO3 was observed at 648 ± 15 and 723 ± 15 °C respectively by differential thermal analysis and confirmed by dielectric spectroscopy and high temperature powder X-ray diffraction.

  16. Influence of Bi2O3 on the Structure and Dielectric Properties of Ag(Nb0.8Ta0.2)O3 Ceramics%Bi2O3掺杂对Ag(Nb0.8Ta0.2)O3陶瓷结构和介电性能的影响

    Institute of Scientific and Technical Information of China (English)

    肖谧; 杨朝; 钟小蓉; 席芳芳

    2014-01-01

    本文研究了Bi2O3掺杂对Ag(Nb0.8Ta0.2)O3陶瓷的结构和介电性能的影响.X射线衍射(XRD)结果表明,Bi2O3的掺杂可以使陶瓷中Ag+被还原并析出,且银析出的量随Bi2O3掺杂量的增加而不断增加,这可能源自于Bi3+对Ag+的取代.在一定范围内增大Bi2O3掺杂量可提高Ag(Nb0.8Ta0.2)O3陶瓷的室温介电常数,降低介电损耗,并使温度系数向负值方向移动.当Bi2O3的掺杂量约为3.5wt%时,样品具有较大的介电常数(ε=672)和较小的介电损耗(tarδ=7.3×10-4).

  17. High field superconducting magnets

    Science.gov (United States)

    Hait, Thomas P. (Inventor); Shirron, Peter J. (Inventor)

    2011-01-01

    A superconducting magnet includes an insulating layer disposed about the surface of a mandrel; a superconducting wire wound in adjacent turns about the mandrel to form the superconducting magnet, wherein the superconducting wire is in thermal communication with the mandrel, and the superconducting magnet has a field-to-current ratio equal to or greater than 1.1 Tesla per Ampere; a thermally conductive potting material configured to fill interstices between the adjacent turns, wherein the thermally conductive potting material and the superconducting wire provide a path for dissipation of heat; and a voltage limiting device disposed across each end of the superconducting wire, wherein the voltage limiting device is configured to prevent a voltage excursion across the superconducting wire during quench of the superconducting magnet.

  18. Superconductivity above 10 K in Non-Cuprate Oxides

    OpenAIRE

    Johnston, David C.

    2010-01-01

    Beginning in 1973, several non-cuprate transition metal and non-transition metal oxides were discovered with superconducting transition temperatures between 10 and 30 K. Retrospectives about these discoveries in spinel structure LiTi2O4 and perovskite structure (Ba,K)(Bi,Pb)O3 are given.

  19. Localized and mixed valence state of Ce 4 f in superconducting and ferromagnetic CeO1 -xFxBiS2 revealed by x-ray absorption and photoemission spectroscopy

    Science.gov (United States)

    Sugimoto, T.; Ootsuki, D.; Paris, E.; Iadecola, A.; Salome, M.; Schwier, E. F.; Iwasawa, H.; Shimada, K.; Asano, T.; Higashinaka, R.; Matsuda, T. D.; Aoki, Y.; Saini, N. L.; Mizokawa, T.

    2016-08-01

    We have performed Ce L3-edge x-ray absorption spectroscopy (XAS) and Ce 4 d -4 f resonant photoemission spectroscopy (PES) on single crystals of CeO1 -xFxBiS2 for x =0.0 and 0.5 in order to investigate the Ce 4 f electronic states. In Ce L3-edge XAS, a mixed valence of Ce was found in the x =0.0 sample, and F doping suppressed it, which is consistent with the results on polycrystalline samples. As for resonant PES, we found that the Ce 4 f electrons in both x =0.0 and 0.5 systems respectively formed a flat band at 1.0 and 1.4 eV below the Fermi level and there was no contribution to the Fermi surfaces. Interestingly, Ce valence in CeOBiS2 deviates from Ce3 + even though Ce 4 f electrons are localized, indicating the Ce valence is not in a typical valence fluctuation regime. We assume that localized Ce 4 f in CeOBiS2 is mixed with unoccupied Bi 6 pz , which is consistent with a previous local structural study. Based on the analysis of the Ce L3-edge XAS spectra using Anderson's impurity model calculation, we found that the transfer integral becomes smaller, increasing the number of Ce 4 f electrons upon the F substitution for O.

  20. Superconductivity Bordering Rashba Type Topological Transition

    Energy Technology Data Exchange (ETDEWEB)

    Jin, M. L.; Sun, F.; Xing, L. Y.; Zhang, S. J.; Feng, S. M.; Kong, P. P.; Li, W. M.; Wang, X. C.; Zhu, J. L.; Long, Y. W.; Bai, H. Y.; Gu, C. Z.; Yu, R. C.; Yang, W. G.; Shen, G. Y.; Zhao, Y. S.; Mao, H. K.; Jin, C. Q.

    2017-01-04

    Strong spin orbital interaction (SOI) can induce unique quantum phenomena such as topological insulators, the Rashba effect, or p-wave superconductivity. Combining these three quantum phenomena into a single compound has important scientific implications. Here we report experimental observations of consecutive quantum phase transitions from a Rashba type topological trivial phase to topological insulator state then further proceeding to superconductivity in a SOI compound BiTeI tuned via pressures. The electrical resistivity measurement with V shape change signals the transition from a Rashba type topological trivial to a topological insulator phase at 2 GPa, which is caused by an energy gap close then reopen with band inverse. Superconducting transition appears at 8 GPa with a critical temperature TC of 5.3 K. Structure refinements indicate that the consecutive phase transitions are correlated to the changes in the Bi–Te bond and bond angle as function of pressures. The Hall Effect measurements reveal an intimate relationship between superconductivity and the unusual change in carrier density that points to possible unconventional superconductivity.

  1. Superconductivity Bordering Rashba Type Topological Transition

    Science.gov (United States)

    Jin, M. L.; Sun, F.; Xing, L. Y.; Zhang, S. J.; Feng, S. M.; Kong, P. P.; Li, W. M.; Wang, X. C.; Zhu, J. L.; Long, Y. W.; Bai, H. Y.; Gu, C. Z.; Yu, R. C.; Yang, W. G.; Shen, G. Y.; Zhao, Y. S.; Mao, H. K.; Jin, C. Q.

    2017-01-01

    Strong spin orbital interaction (SOI) can induce unique quantum phenomena such as topological insulators, the Rashba effect, or p-wave superconductivity. Combining these three quantum phenomena into a single compound has important scientific implications. Here we report experimental observations of consecutive quantum phase transitions from a Rashba type topological trivial phase to topological insulator state then further proceeding to superconductivity in a SOI compound BiTeI tuned via pressures. The electrical resistivity measurement with V shape change signals the transition from a Rashba type topological trivial to a topological insulator phase at 2 GPa, which is caused by an energy gap close then reopen with band inverse. Superconducting transition appears at 8 GPa with a critical temperature TC of 5.3 K. Structure refinements indicate that the consecutive phase transitions are correlated to the changes in the Bi–Te bond and bond angle as function of pressures. The Hall Effect measurements reveal an intimate relationship between superconductivity and the unusual change in carrier density that points to possible unconventional superconductivity.

  2. Theory of superconductivity

    CERN Document Server

    Crisan, Mircea

    1989-01-01

    This book discusses the most important aspects of the theory. The phenomenological model is followed by the microscopic theory of superconductivity, in which modern formalism of the many-body theory is used to treat most important problems such as superconducting alloys, coexistence of superconductivity with the magnetic order, and superconductivity in quasi-one-dimensional systems. It concludes with a discussion on models for exotic and high temperature superconductivity. Its main aim is to review, as complete as possible, the theory of superconductivity from classical models and methods up t

  3. Tuning of dielectric, pyroelectric and ferroelectric properties of 0.715Bi0.5Na0.5TiO3-0.065BaTiO3-0.22SrTiO3 ceramic by internal clamping

    Directory of Open Access Journals (Sweden)

    Satyanarayan Patel

    2015-08-01

    Full Text Available This study systematically investigates the phenomenon of internal clamping in ferroelectric materials through the formation of glass-ceramic composites. Lead-free 0.715Bi0.5Na0.5TiO3−0.065BaTiO3−0.22SrTiO3 (BNT-BT-ST bulk ferroelectric ceramic was selected for the course of investigation. 3BaO − 3TiO2 − B2O3 (BTBO glass was then incorporated systematically to create sintered samples containing 0%, 2%, 4% and 6% glass (by weight. Upon glass induction features like remnant polarization, saturation polarization, hysteresis losses and coercive field could be varied as a function of glass content. Such effects were observed to benefit derived applications like enhanced energy storage density ∼174 kJ/m3 to ∼203 kJ/m3 and pyroelectric coefficient 5.7x10−4 Cm−2K−1 to 6.8x10−4 Cm−2K−1 by incorporation of 4% glass. Additionally, BNT-BT-ST depolarization temperature decreased from 457K to 431K by addition of 4% glass content. Glass incorporation could systematically increases diffuse phase transition and relaxor behavior temperature range from 70 K to 81K and 20K to 34 K, respectively when 6% and 4% glass content is added which indicates addition of glass provides better temperature stability. The most promising feature was observed to be that of dielectric response tuning. It can be also used to control (to an extent the dielectric behavior of the host ceramic. Dielectric permittivity and losses decreased from 1278 to 705 and 0.109 to 0.107 for 6% glass, at room temperature. However this reduction in dielectric constant and loss increases pyroelectric figures of merit (FOMs for high voltage responsivity (Fv high detectivity (Fd and energy harvesting (Fe from 0.018 to 0.037 m2C−1, 5.89 to 8.85 μPa−1/2 and 28.71 to 61.55 Jm−3K−2, respectively for 4% added ceramic-glass at room temperature. Such findings can have huge implications in the field of tailoring ferroelectric response for application specific requirements.

  4. Superconductivity in Bismuth. A New Look at an Old Problem

    Science.gov (United States)

    2016-01-01

    To investigate the relationship between atomic topology, vibrational and electronic properties and superconductivity of bismuth, a 216-atom amorphous structure (a-Bi216) was computer-generated using our undermelt-quench approach. Its pair distribution function compares well with experiment. The calculated electronic and vibrational densities of states (eDOS and vDOS, respectively) show that the amorphous eDOS is about 4 times the crystalline at the Fermi energy, whereas for the vDOS the energy range of the amorphous is roughly the same as the crystalline but the shapes are quite different. A simple BCS estimate of the possible crystalline superconducting transition temperature gives an upper limit of 1.3 mK. The e-ph coupling is more preponderant in a-Bi than in crystalline bismuth (x-Bi) as indicated by the λ obtained via McMillan’s formula, λc = 0.24 and experiment λa = 2.46. Therefore with respect to x-Bi, superconductivity in a-Bi is enhanced by the higher values of λ and of eDOS at the Fermi energy. PMID:26815431

  5. Ferroelectric Domain Structure and Local Piezoelectric Properties of Lead-Free (Ka0.5Na0.5)NbO3 and BiFeO3-Based Piezoelectric Ceramics

    OpenAIRE

    Denis Alikin; Anton Turygin; Andrei Kholkin; Vladimir Shur

    2017-01-01

    Recent advances in the development of novel methods for the local characterization of ferroelectric domains open up new opportunities not only to image, but also to control and to create desired domain configurations (domain engineering). The morphotropic and polymorphic phase boundaries that are frequently used to increase the electromechanical and dielectric performance of ferroelectric ceramics have a tremendous effect on the domain structure, which can serve as a signature of complex pola...

  6. Research On Bi-Based High-Temperature Superconductors

    Science.gov (United States)

    Banks, Curtis; Doane, George B., III; Golben, John

    1993-01-01

    Brief report describes effects of melt sintering on Bi-based high-temperature superconductor system, as well as use of vibrating-sample magnetometer to determine hysteresis curves at 77 K for partially melt-sintered samples. Also discussed is production of high-temperature superconducting thin films by laser ablation: such films potentially useful in detection of signals of very low power.

  7. Agile BI – The Future of BI

    Directory of Open Access Journals (Sweden)

    Mihaela MUNTEAN

    2013-01-01

    Full Text Available In a rapidly changing economy, Business Intelligence solutions have to become more agile. This paper attempts to discuss some questions which help in creating an agile BI solution such as: What is Agile? Why agile is so well suited for BI? Which are the key elements that promote an agile BI solution? Also, this paper briefly looks at technologies that can be used for enabling an agile BI solution.

  8. More superconductivity questions than answers.

    Science.gov (United States)

    Robinson, A L

    1987-07-17

    Although making liquid nitrogen-temperature superconductors is easy enough that high school science projects already feature them, researchers still have little idea how the new ceramic oxides work and therefore little guidance for improving them. At the International Workshop on Novel Mechanisms of Superconductivity, held from 22 to 26 June in Berkeley, California, theorists reviewed a host of competing explanations of how these materials come by their remarkable properties, but they could not, get far in sifting through the candidates for the best one. One cause of the unsettled situation is that theorists have not yet pushed their models far enough to make many specific predictions about physical properties and therefore to provide a reason to choose one theory over another. But experimental data for comparison with theory are lacking, too. For example, experimentalists are just now succeeding in being able to grow single crystals and thin films of the ceramic oxide superconductors, whose properties were shown at the workshop to be highly anisotropic. Measurements already made on the polycrystalline sintered material available up to now are difficult to interpret and therefore need to be repeated on good-quality crystals and films, where the variation of properties with crystallographic orientation can be mapped out. Given the high level of Japanese activity in the field, it was surprising that no researchers from industrial laboratories in Japan presented their findings at the workshop. In the light of a budding international competition in commercializing superconductors, some American scientists interpreted the absence as an attempt to protect proprietary advances. A more pleasant surprise was the attendance of a delegation of six Soviet scientists, although one of the fathers of superconductivity theory, Vitaly Ginzburg of the P.N.Lebedev Institute of Physics in Moscow, who was expected, did not come.

  9. Preparation of granular Bi-2212 nanowires by electrospinning

    Science.gov (United States)

    Zeng, Xian Lin; Koblischka, Michael R.; Karwoth, Thomas; Hauet, Thomas; Hartmann, Uwe

    2017-03-01

    Bi2Sr2CaCu2O8 (Bi-2212) superconducting nanowires are synthesized by the electrospinning method. Two different precursors were employed to grow the nanowires, a Pb-doped one and a Cu,Ca-enriched one. The granular polycrystalline character was confirmed by scanning electron microscopy and x-ray diffraction measurement. The magnetic and electric properties of the samples were investigated via SQUID magnetometry and four-probe resistance measurements. The superconducting transition temperatures of the two systems were found to be similar (Pb-doped 84 K, Cu,Ca-enriched 76 K), but the transition width and the onset of irreversibility were clearly different. The magnetization loops and the resistance data demonstrate that the Cu,Ca-enriched precursor yields samples with better superconducting properties.

  10. Heterostructures of Bi-4334 and MgB2 superconductors

    Science.gov (United States)

    Padmavathi, M.; Singh, R.

    2016-05-01

    We report the studies on hetero structures of Bi-4334 and MgB2 superconductors. The two superconductors were arranged in the form of bulk multilayers using hydraulic pressure system. X-ray diffraction pattern and dc magnetization studies confirm the presence of both superconducting phases in this try-layer hetero structured sample. The d.c magnetization shows the superconducting onset at 77K and 39K for Bi-4334 and MgB2 phases respectively. Critical current density (Jc) is calculated from hysteresis loop of the sample in both in-plane field and out of plane field configurations. Inverted anisotropy in Jc is observed due to enhancement of ab-plane properties because of multilayer growth process. Morphology of the samples at surface and interface of two superconducting layers is discussed in view of Field emission scanning electron microscopy.

  11. Lattice dynamics of Ba{sub 1-x}K{sub x}BiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Green, M.A. [Royal Institution of Great Britain, London (United Kingdom); Prassides, K. [Royal Institution of Great Britain, London (United Kingdom)]|[School of Chemistry and Molecular Science, Sussex Univ., Brighton (United Kingdom); Day, P. [Royal Institution of Great Britain, London (United Kingdom); Neumann, D.A. [Research Radiation Div., National Inst. of Standards and Technology, Gaithersburg, MD (United States)

    1995-04-01

    Neutron weighted density-of-states measurements of Ba{sub 1-x}K{sub x}BiO{sub 3} are presented which show pronounced changes as a function of both temperature and Bi oxidation states. Information is gained on both the structural and metal-insulator transitions occurring with increased potassium doping. Phonon anomalies associated with the appearance of a superconducting energy gap gives strong evidence of electron-phonon coupling and superconductivity via a conventional BCS mechanism. (orig.)

  12. Experiments on normal zone propagation properties in BSCCO silver sheathed tapes; Bi kei sankabutsu chodendo senzai no jodendo denpa tokusei jikken

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, S.; Ishiyama, A. [Waseda Univ., Tokyo (Japan); Kasu, O.; Ii, H.; Takeda, K.; Shibuya, M. [Engineering Research Association for Superconductive Generation Equipment and Materials, Osaka (Japan)

    1999-06-07

    In the design of the superconducting coil, the elucidation of normal conduction propagation characteristics and quenching process of the coil becomes indispensable information for the protection design of the coil in the quenching. Operating condition and electrical thermal characteristic are different on oxide superconducting wire rod driven in the high temperature. Therefore, there are quench characteristics of metal system superconducting wire rod unlike the case. Experiment and analysis of the Bi-2223/Ag polycore tape superconducting wire rod in which until now authors normal conduction transfer are carried out, and the result has been reported. In this report, in making Bi-2212/Ag polycore tape superconducting wire rod and Bi-2223/Ag multilayer tape superconducting wire rod to be a sample, the measurement experiment was carried out on normal conduction propagation characteristics in the conduction cooling operation by the GM refrigerating machine to wire rod long hand direction. (NEDO)

  13. Ceramic Seal.

    Energy Technology Data Exchange (ETDEWEB)

    Smartt, Heidi A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Romero, Juan A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Custer, Joyce Olsen [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hymel, Ross W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Krementz, Dan [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Gobin, Derek [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Harpring, Larry [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Martinez-Rodriguez, Michael [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Varble, Don [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); DiMaio, Jeff [Tetramer Technologies, Pendleton, SC (United States); Hudson, Stephen [Tetramer Technologies, Pendleton, SC (United States)

    2016-11-01

    Containment/Surveillance (C/S) measures are critical to any verification regime in order to maintain Continuity of Knowledge (CoK). The Ceramic Seal project is research into the next generation technologies to advance C/S, in particular improving security and efficiency. The Ceramic Seal is a small form factor loop seal with improved tamper-indication including a frangible seal body, tamper planes, external coatings, and electronic monitoring of the seal body integrity. It improves efficiency through a self-securing wire and in-situ verification with a handheld reader. Sandia National Laboratories (SNL) and Savannah River National Laboratory (SRNL), under sponsorship from the U.S. National Nuclear Security Administration (NNSA) Office of Defense Nuclear Nonproliferation Research and Development (DNN R&D), have previously designed and have now fabricated and tested Ceramic Seals. Tests have occurred at both SNL and SRNL, with different types of tests occurring at each facility. This interim report will describe the Ceramic Seal prototype, the design and development of a handheld standalone reader and an interface to a data acquisition system, fabrication of the seals, and results of initial testing.

  14. Simple Superconducting "Permanent" Electromagnet

    Science.gov (United States)

    Israelson, Ulf E.; Strayer, Donald M.

    1992-01-01

    Proposed short tube of high-temperature-superconducting material like YBa2Cu3O7 acts as strong electromagnet that flows as long as magnetic field remains below critical value and temperature of cylinder maintained sufficiently below superconducting-transition temperature. Design exploits maximally anisotropy of high-temperature-superconducting material.

  15. Basic principle of superconductivity

    OpenAIRE

    De Cao, Tian

    2007-01-01

    The basic principle of superconductivity is suggested in this paper. There have been two vital wrong suggestions on the basic principle, one is the relation between superconductivity and the Bose-Einstein condensation (BEC), and another is the relation between superconductivity and pseudogap.

  16. Dramatic influence of Dy{sup 3+} doping on strain and domain structure in lead-free piezoelectric 0.935(Na{sub 1/2}Bi{sub 1/2})TiO{sub 3}−0.065BaTiO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Li, C. Q.; Zhang, J. Z.; Hu, Z. G., E-mail: zghu@ee.ecnu.edu.cn; Chu, J. H. [Department of Electronic Engineering, East China Normal University, Shanghai 200241 (China); Yao, Q. R.; Wang, F. F.; Liu, A. Y.; Shi, W. Z. [Department of Physics, Shanghai Normal University, Shanghai 200234 (China)

    2015-12-15

    An electric-field induced giant strain response and doping level dependent domain structural variations have been studied in the dysprosium (Dy{sup 3+})-modified 0.935(Na{sub 1/2}Bi{sub 1/2})TiO{sub 3}-0.065BaTiO{sub 3}(xDy : NBBT) ceramics with the doping levels of 0%, 0.5%, 1%, and 2%. X-ray diffraction and Raman spectroscopy analyses not only demonstrates the change in ionic configurations induced by Dy{sup 3+} doping, but also shows the local crystal symmetry for x ≥ 0.5% doping levels to deviate from the idealized cubic structure. Piezoresponse force microscopy measurement exhibits the presence of an intermediate phase with orthorhombic symmetry at the critical Dy{sup 3+} doping level of 2%. Moreover, at this doping level, a giant recoverable nonlinear strain of ∼0.44% can be observed with high normalized strain (S{sub max}/E{sub max}) of 728 pm/V. At the same applied field, the strain exhibits a 175% increase than that of NBBT ceramic. Such a large strain stems from the varying coherence lengths of polar nanoregions (PNRs) and an unusual reversible 90° domain switching caused by the symmetry conforming property of point defects, where the restoring force is provided by unswitchable defects. The mechanism reveals a new possibility to achieve large electric-field strain effect for a wide range of ferroelectric systems, which can lead to applications in novel “on-off” actuators.

  17. The effects of Ag, Mg, and Pr doping on the superconductivity and structure of BSCCO

    Science.gov (United States)

    Boussouf, N.; Mosbah, M.-F.; Guerfi, T.; Bouaïcha, F.; Chamekh, S.; Amira, A.

    2009-11-01

    The influence of Ag, Mg, and Pr additions and co-additions on microstructure and phase formation of Bi2Sr2CaCu2O8+d (Bi2212) system is investigated. Polycrystalline Bi2212 samples were synthesized in air by solid state reaction method. Phase analysis, micro structural observations and magnetic properties were carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) and A.C. susceptibility measurements respectively. XRD results reveal two main phases (Bi-2201 and Bi2212). SEM photographs show that the substitution by Ag, Mg or Pr affects the mechanism of the grains growth. The undoped sample has a critical temperature Tc of 65 K while in the Mg and Ag containing compounds the Tc is 77 K and 75 K respectively. The Pr containing compound exhibits no superconductivity. A valence of the Pr ion higher than 3+ in the lattice supports the holefilling mechanism of the suppression of superconductivity.

  18. Structural phase stability and electric field induced relaxor–ferroelectric phase transition in (1 − x)(Bi{sub 0.5}Na{sub 0.5})TiO{sub 3}–xBaTiO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Anthoniappen, J., E-mail: jesusvd@gmail.com [Graduate Institute of Applied Science and Engineering, Fu Jen Catholic University, New Taipei City 24205, Taiwan (China); Department of Physics, University of San Carlos, Cebu City 6000 (Philippines); Tu, C.S. [Graduate Institute of Applied Science and Engineering, Fu Jen Catholic University, New Taipei City 24205, Taiwan (China); Department of Physics, Fu Jen Catholic University, New Taipei City 24205, Taiwan (China); Chen, P.-Y. [Department of Mechanical Engineering, Ming-Chi University of Technology, New Taipei City 24301, Taiwan (China); Chen, C.-S. [Department of Mechanical Engineering, Hwa-Hsia Institute of Technology, New Taipei City 23567, Taiwan (China); Chiu, S.-J.; Lee, H.-Y. [National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan (China); Ting, Yi; Wang, S.-F. [Department of Physics, Fu Jen Catholic University, New Taipei City 24205, Taiwan (China); Chai, C.-K. [Department of Mechanical Engineering, Ming-Chi University of Technology, New Taipei City 24301, Taiwan (China)

    2015-01-05

    Highlights: • The well-known MPB compositions of [(1 − x)(Bi{sub 0.5}Na{sub 0.5})TiO{sub 3}–xBaTiO{sub 3}] (x = 0.06, 0.07 and 0.075) show a transition sequence of rhombohedral + tetragonal − tetragonal − cubic phases as a function of temperature. Functionally important two-phase coexists from room temperature to 200 °C. • The frequency-dispersion anomaly at lower temperatures indicates a progressive transition from ferroelectric to relaxor state upon heating. Therefore, phase coexistence plays a vital role in relaxor ferroelectric behavior among BNT–BT compositions. • The non-ergodic relaxor phase can be transformed into ferroelectric phase by dc poling field. - Abstract: Structure, phase transition, and dielectric relaxor behavior have been investigated in morphotropic phase boundary compositions of (1 − x)(Bi{sub 0.5}Na{sub 0.5})TiO{sub 3}-xBaTiO{sub 3} ceramics for x = 0.06, 0.07, and 0.075. In-situ structural thermal stability has been analyzed by using high-resolution synchrotron X-ray diffraction as a function of temperature. A transition sequence of rhombohedral + tetragonal − tetragonal − cubic phases is observed upon heating. The “rhombohedral + tetragonal” indicates a coexistence of rhombohedral R3c and tetragonal P4bm phases. The two-phase coexistence extends from room temperature to 200 °C. Zero-field dielectric permittivity reveals a frequency dispersion at low temperature region (T < T{sub m}) and polar nanoregions below Burns temperature (T{sub B}). The two-phase coexistence plays a vital role for frequency dispersion below T{sub m}. Dielectric spectra of pre-poled samples reveal a field-induced ferroelectric−relaxor phase transition at depolarization temperature T{sub d}.

  19. Electrical conduction in (Na0.125Bi0.125Ba0.65Ca0.1)(Nd0.065Ti0.87Nb0.065)O3 ceramic

    Indian Academy of Sciences (India)

    Syed Mahboob; G Prasad; G S Kumar

    2006-02-01

    Polycrystalline ceramic samples of sodium bismuth titanate with simultaneous doping at A and B sites have been studied for the influence of these dopants on the electrical conduction mechanism. A.C. conductivity measurements were done on the prepared sample in a wide range of frequency and temperature. These studies revealed that the conduction in the sample arises due to hopping of bound charges. Four-term power law is used to characterize the frequency dependence of a.c. conductivity. From the temperature dependence of the exponents, the a.c. conduction in the samples is explained.

  20. Modeling constrained sintering of bi-layered tubular structures

    DEFF Research Database (Denmark)

    Tadesse Molla, Tesfaye; Kothanda Ramachandran, Dhavanesan; Ni, De Wei;

    2015-01-01

    . Furthermore, the model is validated using densification results from sintering of bi-layered tubular ceramic oxygen membrane based on porous MgO and Ce0.9Gd0.1O1.95-d layers. Model input parameters, such as the shrinkage kinetics and viscous parameters are obtained experimentally using optical dilatometry...

  1. Superconducting microfabricated ion traps

    CERN Document Server

    Wang, Shannon X; Labaziewicz, Jaroslaw; Dauler, Eric; Berggren, Karl; Chuang, Isaac L

    2010-01-01

    We fabricate superconducting ion traps with niobium and niobium nitride and trap single 88Sr ions at cryogenic temperatures. The superconducting transition is verified and characterized by measuring the resistance and critical current using a 4-wire measurement on the trap structure, and observing change in the rf reflection. The lowest observed heating rate is 2.1(3) quanta/sec at 800 kHz at 6 K and shows no significant change across the superconducting transition, suggesting that anomalous heating is primarily caused by noise sources on the surface. This demonstration of superconducting ion traps opens up possibilities for integrating trapped ions and molecular ions with superconducting devices.

  2. Superconducting material development

    Science.gov (United States)

    1987-09-01

    A superconducting compound was developed that showed a transition to a zero-resistance state at 65 C, or 338 K. The superconducting material, which is an oxide based on strontium, barium, yttrium, and copper, continued in the zero-resistance state similar to superconductivity for 10 days at room temperature in the air. It was also noted that measurements of the material allowed it to observe a nonlinear characteristic curve between current and voltage at 65 C, which is another indication of superconductivity. The research results of the laboratory experiment with the superconducting material will be published in the August edition of the Japanese Journal of Applied Physics.

  3. Anomalous behaviors in resistivity and magnetization of reduction-treated multi phase ceramics of Pr124/Pr123 and inhomogeneous Pr247

    Energy Technology Data Exchange (ETDEWEB)

    Hagiwara, M., E-mail: hag@kit.ac.j [Faculty of Engineering and Design, Kyoto Institute of Technology, Kyoto (Japan); Shima, T. [Advanced Technology Center, Kyoto Institute of Technology, Kyoto (Japan); Tanaka, S. [Faculty of Engineering and Design, Kyoto Institute of Technology, Kyoto (Japan); Koyama, K. [Faculty of Integrated Arts and Sciences, University of Tokushima, Tokushima (Japan)

    2010-12-15

    A superconductive sign found in electric resistivity behavior of mixed ceramic Pr124/Pr123 is searched and discussed, to advance preceding discussion about the superconductive region induced by intergrain charge transfer effect in ceramic Pr247 containing the related impurity phases. Observed reduction effects for largely impure ceramic of Pr247 with Pr124 and Pr123 and for simply dual-phase sample of Pr124/Pr123 inform us that the oxygen-reduction brings not only superconductive electron doping but also normal resistivity enhancement. Milder heat treatment condition is expected to assist possible attainment of zero-resistivity for Pr124/Pr123.

  4. Protective link for superconducting coil

    Science.gov (United States)

    Umans, Stephen D.

    2009-12-08

    A superconducting coil system includes a superconducting coil and a protective link of superconducting material coupled to the superconducting coil. A rotating machine includes first and second coils and a protective link of superconducting material. The second coil is operable to rotate with respect to the first coil. One of the first and second coils is a superconducting coil. The protective link is coupled to the superconducting coil.

  5. Superconductivity in transition metals.

    Science.gov (United States)

    Slocombe, Daniel R; Kuznetsov, Vladimir L; Grochala, Wojciech; Williams, Robert J P; Edwards, Peter P

    2015-03-13

    A qualitative account of the occurrence and magnitude of superconductivity in the transition metals is presented, with a primary emphasis on elements of the first row. Correlations of the important parameters of the Bardeen-Cooper-Schrieffer theory of superconductivity are highlighted with respect to the number of d-shell electrons per atom of the transition elements. The relation between the systematics of superconductivity in the transition metals and the periodic table high-lights the importance of short-range or chemical bonding on the remarkable natural phenomenon of superconductivity in the chemical elements. A relationship between superconductivity and lattice instability appears naturally as a balance and competition between localized covalent bonding and so-called broken covalency, which favours d-electron delocalization and superconductivity. In this manner, the systematics of superconductivity and various other physical properties of the transition elements are related and unified.

  6. Superconducting materials suitable for magnets

    CERN Document Server

    CERN. Geneva. Audiovisual Unit

    2002-01-01

    The range of materials available for superconducting magnets is steadily expanding, even as the choice of material becomes potentially more complex. When virtually all magnets were cooled by helium at ~2-5 K it was easy to separate the domain of Nb-Ti from those of Nb3Sn applications and very little surprise that more than 90% of all magnets are still made from Nb-Ti. But the development of useful conductors of the Bi-Sr-Ca-Cu-O and YBa2Cu3Ox high temperature superconductors, coupled to the recent discovery of the 39 K superconductor MgB2 and the developing availability of cryocoolers suggests that new classes of higher temperature, medium field magnets based on other than Nb-based conductors could become available in the next 5-10 years. My talks will discuss the essential physics and materials science of these 5 classes of material - Nb-Ti, Nb3Sn, MgB2, Bi-Sr-Ca-Cu-O and YBa2Cu3Ox - in the context of those aspects of their science, properties and fabrication properties, which circumscribe their applications...

  7. High-power piezoelectric characteristics of textured bismuth layer structured ferroelectric ceramics.

    Science.gov (United States)

    Ogawa, Hirozumi; Kawada, Shinichiro; Kimura, Masahiko; Shiratsuyu, Kousuke; Sakabe, Yukio

    2007-12-01

    Abstract-The high-power piezoelectric characteristics in h001i oriented ceramics of bismuth layer structured ferroelectrics (BLSF), SrBi(2)Nb(2)O(9) (SBN), (Bi,La)(4)Ti(3)O(12) (BLT), and CaBi(4)Ti(4)O(15) (CBT), were studied by a constant voltage driving method. These textured ceramics were fabricated by a templated grain growth (TGG) method, and their Lotgering factors were 95%, 97%, and 99%, respectively. The vibration velocities of the longitudinal mode (33-mode) increased proportionally to an applied electric field up to 2.5 m/s in these textured BLSF ceramics, although, the vibration velocity of the 33-mode was saturated at more than 1.0 m/s in the Pb(Mn,Nb)O(3)-PZT ceramics. The resonant frequencies were constant up to the vibration velocity of 2.5 m/s in the SBN and CBT textured ceramics; however, the resonant frequency decreased with increasing over the vibration velocity of 1.5 m/s in the BLT textured ceramics. The dissipation power density of the BLT was almost the same as that of the Pb(Mn,Nb)O(3)-PZT ceramics. However, the dissipation power densities of the SBN and CBT were lower than those of the BLT and Pb(Mn,Nb)O(3)-PZT ceramics. The textured SBN and CBT ceramics are good candidates for high-power piezoelectric applications.

  8. Dielectric and magnetic properties of Ta sub 2 O sub 5 -doped PrFeO sub 3 -PbTiO sub 3 and PrFeO sub 3 -BiFeO sub 3 ceramics

    CERN Document Server

    Kim, J S; Choi, Y N; Jang, P W

    2003-01-01

    Polarization-electric field (P-E) and magnetization-magnetic field (M-H) hysteresis curves have been characterized in the solid solutions of (1-x)PrFeO sub 3 -xPbTiO sub 3 +yTa sub 2 O sub 5 (y = 0-0.015 mole) and 0.2PrFeO sub 3 -0.8BiFeO sub 3. Neutron and X-ray diffraction data were collected for crystal structural analysis. The (1-x)PrFeO sub 3 -xPbTiO sub 3 were ferromagnetic at 0.2 = 0.7 from Pbnm (a = 5.552, b = 5.540 A, c = 7.833 A) to I4cm (a = b = 5.54 A, c = 7.841A) The structural analysis indicates that the solid solutions are ferroelectric only at x > 0.6. The 0.2PrFeO sub 3 -0.8BiFeO sub 3 showed a spontaneous magnetization of 0.3 emu/g at room temperature and remanent polarization P sub r of 0.6 mu C/cm sup 2. Addition of Ta sub 2 O sub 5 substantially changed the magnetic properties. The antiferromagnetic ordering is considered not to have a direct relationship with the weak ferromagnetism observed in this system. (author)

  9. Effects of critical fluctuations and dimensionality on the jump in specific heat at the superconducting transition temperature: Application to YBa2Cu3O7 -δ ,Bi2Sr2CaCu2O8 +δ , and KOs2O6 compounds

    Science.gov (United States)

    Keumo Tsiaze, R. M.; Wirngo, A. V.; Mkam Tchouobiap, S. E.; Fotue, A. J.; Baloïtcha, E.; Hounkonnou, M. N.

    2016-06-01

    We report on a study of the superconducting order parameter thermodynamic fluctuations in YBa2Cu3O7 -δ ,Bi2Sr2CaCu2O8 +δ , and KOs2O6 compounds. A nonperturbative technique within the framework of the renormalized Gaussian approach is proposed. The essential features are reported (analytically and numerically) through Ginzburg-Landau (GL) model-based calculations which take into account both the dimension and the microscopic parameters of the system. By presenting a self-consistent approach improvement on the GL theory, a technique for obtaining corrections to the asymptotic critical behavior in terms of nonuniversal parameters is developed. Therefore, corrections to the specific heat and the critical transition temperature for one-, two-, and three-dimensional samples are found taking into account the fact that fluctuations occur at all length scales as the critical point of a system is approached. The GL model in the free-field approximation and the 3D-X Y model are suitable for describing the weak and strong fluctuation regimes respectively. However, with a modified quadratic coefficient, the renormalized GL model is able to explain certain experimental observations including the specific heat of complicated systems, such as the cup-rate superconductors and the β -pyrochlore oxides. It is clearly shown that the enhancement, suppression, or rounding of the specific heat jump of high-Tc cup-rate superconductors at the transition are indicative of the order parameter thermodynamic fluctuations according to the dimension and the nature of interactions.

  10. Effects of critical fluctuations and dimensionality on the jump in specific heat at the superconducting transition temperature: Application to YBa_{2}Cu_{3}O_{7-δ},Bi_{2}Sr_{2}CaCu_{2}O_{8+δ}, and KOs_{2}O_{6} compounds.

    Science.gov (United States)

    Keumo Tsiaze, R M; Wirngo, A V; Mkam Tchouobiap, S E; Fotue, A J; Baloïtcha, E; Hounkonnou, M N

    2016-06-01

    We report on a study of the superconducting order parameter thermodynamic fluctuations in YBa_{2}Cu_{3}O_{7-δ},Bi_{2}Sr_{2}CaCu_{2}O_{8+δ}, and KOs_{2}O_{6} compounds. A nonperturbative technique within the framework of the renormalized Gaussian approach is proposed. The essential features are reported (analytically and numerically) through Ginzburg-Landau (GL) model-based calculations which take into account both the dimension and the microscopic parameters of the system. By presenting a self-consistent approach improvement on the GL theory, a technique for obtaining corrections to the asymptotic critical behavior in terms of nonuniversal parameters is developed. Therefore, corrections to the specific heat and the critical transition temperature for one-, two-, and three-dimensional samples are found taking into account the fact that fluctuations occur at all length scales as the critical point of a system is approached. The GL model in the free-field approximation and the 3D-XY model are suitable for describing the weak and strong fluctuation regimes respectively. However, with a modified quadratic coefficient, the renormalized GL model is able to explain certain experimental observations including the specific heat of complicated systems, such as the cup-rate superconductors and the β-pyrochlore oxides. It is clearly shown that the enhancement, suppression, or rounding of the specific heat jump of high-T_{c} cup-rate superconductors at the transition are indicative of the order parameter thermodynamic fluctuations according to the dimension and the nature of interactions.

  11. Superconducting Quantum Arrays for Broadband RF Systems

    Science.gov (United States)

    Kornev, V.; Sharafiev, A.; Soloviev, I.; Kolotinskiy, N.; Mukhanov, O.

    2014-05-01

    Superconducting Quantum Arrays (SQAs), homogenous arrays of Superconducting Quantum Cells, are developed for implementation of broadband radio frequency (RF) systems capable of providing highly linear magnetic signal to voltage transfer with high dynamic range, including active electrically small antennas (ESAs). Among the proposed quantum cells which are bi-SQUID and Differential Quantum Cell (DQC), the latter delivered better performance for SQAs. A prototype of the transformer-less active ESA based on a 2D SQA with nonsuperconducting electric connection of the DQCs was fabricated using HYPRES niobium process with critical current density 4.5 kA/cm2. The measured voltage response is characterized by a peak-to-peak swing of ~100 mV and steepness of ~6500 μV/μT.

  12. Impedance spectroscopy studies on (Na0.5Bi0.5)0.94Ba0.06TiO3 + 0.3 wt% Sm2O3 + 0.25 wt% LiF lead-free piezoelectric ceramics

    Indian Academy of Sciences (India)

    N Zidi; A Chaouchi; S D’Astorg; M Rguiti; C Courtois

    2015-06-01

    The a.c. complex impedance spectroscopy technique was used to obtain the electrical parameters of (Na0.5Bi0.5)0.94Ba0.06TiO3 +0.3 wt% Sm2O3 +0.25 wt% LiF lead-free ceramics in a wide frequency range at different temperatures. These samples were prepared by a high-temperature solid-state reaction technique and their single phase formation was confirmed by the X-ray diffraction technique. Dielectric studies exhibit a diffuse phase transition characterized by a temperature and frequency dispersion of permittivity, and this relaxation has been modelled using the modified Curie–Weiss law. The variation of imaginary part (″) of impedance with frequency at various temperatures shows that the ″ values reach a maxima peak (″max) above 400° C. The appearance of single semicircle in the Nyquist plots (″ vs. ′) pattern at high temperatures suggests that the electrical process occurring in the material has a relaxation process possibly due to the contribution for bulk material only. The bulk resistance of the material decreases with rise in temperatures similar to that of a semiconductor, and the Nyquist plot showed the negative temperature coefficient of resistance (NTCR) character of these materials. The frequencies, thermal effect on a.c. conductivity and activation energy have been assessed.

  13. Large Field-Induced Strain Properties of Sr(K0.25Nb0.75) O3-Modified Bi1/2(Na0.82K0.18)1/2TiO3 Lead-Free Piezoelectric Ceramics

    Science.gov (United States)

    Tran, Vu Diem Ngoc; Ullah, Aman; Dinh, Thi Hinh; Lee, Jae-Shin

    2016-05-01

    Lead-free piezoelectric ceramics with compositions of (1 - x)Bi1/2(Na0.82 K0.18)1/2TiO3 + xSr(K0.25Nb0.75)O3, which are abbreviated as (1 - x)BNKT- xSKN with x = 0, 0.01, 0.02, 0.03, 0.04, and 0.05, were synthesized using a conventional solid-state reaction method. The effects of SKN addition on the BNKT system were examined in terms of the phase transition, strain behavior, and ferroelectric and dielectric properties. X-ray diffraction revealed a single perovskite phase for all compositions. The results showed that with increasing SKN content, BNKT-SKN underwent a phase transition from the coexistence of rhombohedral and tetragonal phases to a tetragonal phase. The addition of SKN shifted the depolarization temperature, T d, to a lower temperature and enhanced the diffuseness of the dielectric peaks. The polarization and bipolar strain hysteresis loops of BNKT-SKN showed that the addition of SKN induced a ferroelectric to ergodic relaxor phase transition with a disruption of the ferroelectric order of pure BNKT. As a result, the strain of BNKT-SKN improved significantly with increasing SKN content and reached the highest value of a normalized strain, S max/ E max, of 557 pm/V, when modified with 3 mol.% SKN.

  14. Effect of Lanthanum Doping on Ferroelectric and Strain Properties of 0.96Bi1/2(Na0.84K0.16)1/2TiO3-0.04SrTiO3 Lead-Free Ceramics

    Science.gov (United States)

    Tran, Vu Diem Ngoc; Ullah, Aman; Dinh, Thi Hinh; Lee, Jae-Shin

    2016-05-01

    Lead-free 0.96[Bi1/2(Na0.84K0.16)1/2](1- x)La x TiO3-0.04SrTiO3 (BNKTLa x-ST, with x = 0.00, 0.01, 0.02, 0.03, 0.04, and 0.05) ceramics have been synthesized using a conventional solid-state reaction method and their phase transition, dielectric, ferroelectric, and strain properties investigated. X-ray diffraction patterns revealed formation of pure perovskite phase. A phase transition from coexistence of rhombohedral and tetragonal to a pseudocubic phase was observed at x = 0.02. Polarization and bipolar strain hysteresis loops indicated that the ferroelectric order (FE) of BNKT-ST is significantly disrupted by lanthanum doping. The destabilization of the FE order results in degradation of the remanent polarization, coercive field, depolarization temperature ( T d), electromechanical coupling factor ( k p), and static d 33, accompanied by large electric-field-induced strain of 0.34% at 60 kV/cm with normalized strain of d 33 * = S max/ E max = 600 pm/V at a critical composition of around x = 0.02.

  15. Fabrication and characterization of grain-oriented bismuth vanadate ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Shantha, K.; Varma, K.B.R. [Indian Inst. of Science, Bangalore (India). Materials Research Centre

    1997-11-01

    Grain-oriented (GO; 79%), high density (96% of the theoretical value) ceramics of bismuth vanadate, Bi{sub 2}VO{sub 5.5}, have been fabricated via a liquid-phase-aided two-stage sintering process. Scanning electron microscopy (SEM) was employed to monitor the crystallite size and the morphology of the starting powders and the microstructure of the sintered ceramics. X-ray diffraction (XRD) studies were carried out to verify the grain-orientation in the ceramics. The dielectric constant and the conductivity studies carried out along the directions perpendicular and parallel to the pressing axis show significant anisotropies (1.7 and 5.3, respectively, at 300 K). The grain-oriented ceramics were found to exhibit improved ferroelectric properties, with higher remnant polarization (P{sub r}) and lower coercive field (E{sub c}) than those of the randomly oriented (RO) ceramics.

  16. EXAFS Studies of (Pb,Cd) 1212 phase superconductor and (Bi,Cd)1212 phase compound

    Institute of Scientific and Technical Information of China (English)

    YeTao; ShiqiangWei; 等

    1999-01-01

    We synthesized (Pb,Cd)Sr2(Y,Ca)Cu2O7+x,phase superconductor.After substitution of Pb with Bi,the BiCd1212 phase shows no superconductivity.Although previous EXAFS study has shown the local structure environment of the Cu is similar in both compounds,EXAFS results of Bi and Pb here demonstrate that σ2 of Pb-Oin-plane is larger than that of Bi-O inplane,whereas σ2 of Pb-Oapical is smaller than that of Bi-O,wherase σ2 of Pb-O apical is smaller than that of Bi-Oapical.The Sr shell features are also differnet,it appeared that superconductivity needs some disorder .in carrier reservoir layer,which is due to the substitutional defect caused by different ionic radii.

  17. Characterization of superconducting coil for fault current limitation; Caracterizacao de bobina supercondutora para limitacao de corrente de curto-circuito

    Energy Technology Data Exchange (ETDEWEB)

    Polasek, Alexander; Dias, Rodrigo; Niedu, Daniel Brito; Ogasawara, Tsuneharu; Oliveira Filho, Orsino Borges de; Serra, Eduardo Torres [Centro de Pesquisas de Energia Eletrica (CEPEL), Rio de Janeiro, RJ (Brazil); Gomes Junior, George; Amorim, Helio Salim [Coordenacao dos Programas de Pos-Graduacao em Engeharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil)

    2010-07-01

    The increasing power demand has been raising fault currents up to dangerous levels. Superconducting fault current limiters are a promising solution for this problem. In the present work, we studied a superconducting Bi-2212 coil that is used for fault current limitation. Samples were analyzed by XRD, SEM/EDS and measurement of critical temperature (Tc). The Rietveld method was employed for phase quantification. Relatively high Bi-2212 fractions were found. However, Tc varies from a sample to another one. Variations of local Tc are attributed to variations of oxygen content in Bi- 2212 phase. (author)

  18. Study of vortex dynamics with local magnetic relaxation measurements in the superconducting compound Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}; Etude de la dynamique des vortex par des mesures locales de relaxation magnetique dans le compose supraconducteur Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}

    Energy Technology Data Exchange (ETDEWEB)

    Berry, St

    2000-07-01

    This experimental study of the magnetic field-temperature phase diagram and of the vortex dynamics in high- T{sub c} superconductors focuses on Bismuth-based cuprates: Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}. In type-II superconductors, mixed state characterized by the presence of vortices (quanta of magnetic flux) is divided by a transition line determined by two features of magnetization loops. For T > 40 K, magnetization loops vs applied field show a step evidence of a first order transition. From 20 to 40 K, a second peak replacing the step correspond to an abrupt increase of irreversibility interpreted as a bulk current. We want to understand the nature of the second peak (thermodynamic or nonequilibrium property) and separate phenomena contributing to irreversibility (flux pinning, geometrical or surface effects). Magnetic measurement techniques are nondestructive and have a resolution of few microns. Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} single crystals are optimized by localizing defectives regions with a magneto-optic technique for flux imaging and elimination of these regions with a wire saw. Local magnetization loops and relaxation measurements performed with a microscopic Hall probe array allow to distinguish irreversibility sources. The shape of induction profiles indicates which current dominate between surface current and bulk pinning induced current. Two crossover with time and a direct observation of two phases coexistence in induction profiles enlighten phenomena in play. The measured electric field-current density characteristics lead to barrier energy U(j) controlling thermally activated flux motion. Three relations (U(j) (surface, bulk low and high field) explain second peak. (author)

  19. Aging in the relaxor and ferroelectric state of Fe-doped (1-x)(Bi{sub 1/2}Na{sub 1/2})TiO₃-xBaTiO₃ piezoelectric ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Sapper, Eva; Dittmer, Robert; Rödel, Jürgen [Materials Science Department, Technische Universität Darmstadt, 64287 Darmstadt (Germany); Damjanovic, Dragan [Ceramics Laboratory, École Polytechnique Fédérale de Lausanne, Lausanne 1015 (Switzerland); Erdem, Emre [Institute of Physical Chemistry I, Universität Freiburg, 79104 Freiburg (Germany); Keeble, David J. [Division of Electronic Engineering and Physics, University of Dundee, Dundee DD1 4HN (United Kingdom); Jo, Wook [School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan 689-798 (Korea, Republic of); Granzow, Torsten [Centre de Recherche Public—Gabriel Lippmann, L-4422 Belvaux (Luxembourg)

    2014-09-14

    Aging of piezoelectric properties was investigated in lead-free (1–x)(Bi{sub 1/2}Na{sub 1/2})TiO₃-xBaTiO₃ doped with 1at.% Fe. The relaxor character of the un-poled material prevents macroscopic aging effects, while in the field-induced ferroelectric phase aging phenomena are similar to those found in lead zirconate titanate or barium titanate. Most prominent aging effects are the development of an internal bias field and the decrease of switchable polarization. These effects are temperature activated, and can be explained in the framework of defect complex reorientation. This picture is further supported by electron paramagnetic resonance spectra indicating the existence of (Fe{sub Ti}´-V{sub O}{sup ••}){sup •} defect complexes in the Fe-doped material.

  20. Grain size effect on impedance and modulus properties of (Na0.5Bi0.5TiO3) (1-x) (BaZrO3) x ceramics

    Science.gov (United States)

    Selvamani, Rachna; Singh, Gurvinderjit; Tiwari, V. S.

    2016-05-01

    A complex impedance spectroscopy procedure was utilized to examine the impedance and modulus of (Na0.5Bi0.5TiO3) (1-x) (BaZrO3) x (x = 0.00, 0.03, 0.05 and 0.07) solid solution. The microstructural examinations demonstrate that BaZrO3 acts as a grain development inhibitor. The imaginary part of the impedance plot shows the presence of non-Debye type grain and grain boundary relaxation. The activation energy obtained from impedance and modulus plots was found to increase with an increase in BaZrO3 content. The Cole-Cole investigation reveals a colossal augmentation in the grain boundary resistance with BaZrO3 content. However the grain resistance was observed to be almost the same for all the compositions. These outcomes are clarified on the premise of grain boundary-space charge impact and grain-size.

  1. Preparation and Characterization on Piezo-/Ferro-electric Properties of (1-x)(KNN+LT)+xBI Ceramics%铌钽酸钠钾锂-铟酸铋铁电压电性能的研究

    Institute of Scientific and Technical Information of China (English)

    褚涛; 艾辽东; 龙西法

    2014-01-01

    采用传统固相合成法制备了(1-x)(0.97Na0.5K0.5NbO3+0.03LiTaO3)+xBiInO3[(1-x)(KNN+LT)+xBI]无铅压电陶瓷,研究了该体系的晶体结构、压电、铁电与介电性能.结果表明:(1-x)(KNN+LT)+xBI陶瓷的晶体结构在室温下为正交相和四方相两相共存,随着BI含量的增加,四方相含量逐渐增多,居里温度Tc降低,但是正交四方相转变温度To-t呈现升高趋势,晶格参数逐渐增大.随着BI含量的继续增加,Bi在高温下的挥发导致氧空位的增多,从而使材料性能下降.在x=0.0015时得到组分的最佳性能,其居里温度Tc、相转变温度To-t、压电常数d33剩余极化Pr、矫顽场Ec分别达到400℃、126℃、160 pC/N、19.26 μC/cm2和7.75 kV/cm.

  2. High-Temperature Superconductivity

    Science.gov (United States)

    Tanaka, Shoji

    2006-12-01

    A general review on high-temperature superconductivity was made. After prehistoric view and the process of discovery were stated, the special features of high-temperature superconductors were explained from the materials side and the physical properties side. The present status on applications of high-temperature superconductors were explained on superconducting tapes, electric power cables, magnets for maglev trains, electric motors, superconducting quantum interference device (SQUID) and single flux quantum (SFQ) devices and circuits.

  3. Frontiers in Superconducting Materials

    CERN Document Server

    Narlikar, Anant V

    2005-01-01

    Frontiers in Superconducting Materials gives a state-of-the-art report of the most important topics of the current research in superconductive materials and related phenomena. It comprises 30 chapters written by renowned international experts in the field. It is of central interest to researchers and specialists in Physics and Materials Science, both in academic and industrial research, as well as advanced students. It also addresses electronic and electrical engineers. Even non-specialists interested in superconductivity might find some useful answers.

  4. Superconducting energy recovery linacs

    Science.gov (United States)

    Ben-Zvi, Ilan

    2016-10-01

    High-average-power and high-brightness electron beams from a combination of laser photocathode electron guns and a superconducting energy recovery linac (ERL) is an emerging accelerator science with applications in ERL light sources, high repetition rate free electron lasers , electron cooling, electron ion colliders and more. This paper reviews the accelerator physics issues of superconducting ERLs, discusses major subsystems and provides a few examples of superconducting ERLs.

  5. Superconductive imaging surface magnetometer

    Science.gov (United States)

    Overton, Jr., William C.; van Hulsteyn, David B.; Flynn, Edward R.

    1991-01-01

    An improved pick-up coil system for use with Superconducting Quantum Interference Device gradiometers and magnetometers involving the use of superconducting plates near conventional pick-up coil arrangements to provide imaging of nearby dipole sources and to deflect environmental magnetic noise away from the pick-up coils. This allows the practice of gradiometry and magnetometry in magnetically unshielded environments. One embodiment uses a hemispherically shaped superconducting plate with interior pick-up coils, allowing brain wave measurements to be made on human patients. another embodiment using flat superconducting plates could be used in non-destructive evaluation of materials.

  6. Fundamentals of Superconducting Nanoelectronics

    CERN Document Server

    Sidorenko, Anatolie

    2011-01-01

    This book demonstrates how the new phenomena in superconductivity on the nanometer scale (FFLO state, triplet superconductivity, Crossed Andreev Reflection, synchronized generation etc.) serve as the basis for the invention and development of novel nanoelectronic devices and systems. It demonstrates how rather complex ideas and theoretical models, like odd-pairing, non-uniform superconducting state, pi-shift etc., adequately describe the processes in real superconducting nanostructues and novel devices based on them. The book is useful for a broad audience of readers, researchers, engineers, P

  7. Superconducting optical modulator

    Science.gov (United States)

    Bunt, Patricia S.; Ference, Thomas G.; Puzey, Kenneth A.; Tanner, David B.; Tache, Nacira; Varhue, Walter J.

    2000-12-01

    An optical modulator based on the physical properties of high temperature superconductors has been fabricated and tested. The modulator was constructed form a film of Yttrium Barium Copper Oxide (YBCO) grown on undoped silicon with a buffer layer of Yttria Stabilized Zirconia. Standard lithographic procedures were used to pattern the superconducting film into a micro bridge. Optical modulation was achieved by passing IR light through the composite structure normal to the micro bridge and switching the superconducting film in the bridge region between the superconducting and non-superconducting states. In the superconducting state, IR light reflects from the superconducting film surface. When a critical current is passed through the micro bridge, it causes the film in this region to switch to the non-superconducting state allowing IR light to pass through it. Superconducting materials have the potential to switch between these two states at speeds up to 1 picosecond using electrical current. Presently, fiber optic transmission capacity is limited by the rate at which optical data can be modulated. The superconducting modulator, when combined with other components, may have the potential to increase the transmission capacity of fiber optic lines.

  8. Basic Study of Superconductive Actuator

    OpenAIRE

    涌井, 和也; 荻原, 宏康

    2000-01-01

    There are two kinds of electromagnetic propulsion ships : a superconductive electromagnetic propulsion ship and a superconductive electricity propulsion ship. A superconductive electromagnetic propulsion ship uses the electromagnetic force (Lorenz force) by the interaction between a magnetic field and a electric current. On the other hand, a superconductive electricity propulsion ship uses screws driven by a superconductive motor. A superconductive propulsion ship technique has the merits of ...

  9. Dielectric and Ferroelectric Properties of Nd-Doped Bi4Ti3O12

    Institute of Scientific and Technical Information of China (English)

    Mao Xiangyu; Chen Xiaobing

    2004-01-01

    The investigations on the ferroelectric and dielectric properties of neodymium-doped Bi4Ti3O12 (Bi4-xNdxTi3 O12 ) ferroelectric ceramics were presented. The ferroelectric properties of Bi4Ti3 O12 were improved by Nd-doping.The dielectric property measurements indicate that the Curie temperatures of Bi4-xNdxTi3O12 decrease with Nd-doping.The variations of dielectric loss suggest that the mobility of the domain wall increases and the oxygen vacancy concentration decreases with doping.

  10. 利用高压热处理技术提高Bi-2223/Ag高温超导带材临界电流%ENHANCE THE CRITICAL CURRENT OF BI-2223/AG SUPERCONDUCTING TAPES BY APPLING HIGH PRESSURE SINTERING PROCESS

    Institute of Scientific and Technical Information of China (English)

    瞿体明; 张智巍; 黄凯特; 顾晨; 宋秀华; 韩征和; 曾攀

    2010-01-01

    提高临界电流密度(J_c)对促进Bi-2223/Ag高温超导带材的应用有着重要意义.在常压热处理条件下所制备的带材中存在大量的裂纹、孔洞和第二相颗粒等,这些因素都会对带材的超导连接性能产生破坏作用.我们成功建立了一套可用氧气氛的热等静压设备,工作气压和温度可同时达到15 MPa和850℃.通过引入裂纹愈合热处理过程,我们成功对带材进行了高压热处理,所得样品中第二相颗粒和裂纹数量大幅度降低,77 K、自场下的临界电流相比常压热处理样品提高了20%左右.

  11. 湿法流延制备(Na,K)0.5Bi0.5TiO3织构陶瓷%Fabrication of textured (Na, K)0.5Bi0.5TiO3 ceramics by wet tape-casting

    Institute of Scientific and Technical Information of China (English)

    张昌松; 郭晨洁; 党新安; 杨立军

    2009-01-01

    以NaCl-KCl熔盐法合成的片状Bi4Ti3O12微晶为模板,采用反应模板生长技术(RTGG)和湿法流延工艺制备了织构度为0.70的(Na0.84K0.16)0.5Bi0.5TiO3(NBT-KBT)织构陶瓷.研究了烧结温度对NBT-KBT织构陶瓷的相对密度、微观结构、织构度与电性能的影响.结果表明:其晶粒生长方向与电性能均表现出明显的各向异性,最佳烧结温度为1 150 ℃,在此温度下陶瓷的d33最大为124 pC/N,Pr为7.1×10-5 C/cm2,Ec为3 771 kV/m.

  12. Electrostatic electron-doping yields superconductivity in LaOBiS2

    Science.gov (United States)

    Uesugi, Eri; Nishiyama, Saki; Goto, Hidenori; Ota, Hiromi; Kubozono, Yoshihiro

    2016-12-01

    Electrostatic carrier-doping is attracting serious attention as a meaningful technique for producing interesting electronic states in two-dimensional (2D) layered materials. Ionic-liquid gating can provide the critical carrier density required to induce the metal-insulator transition and superconductivity. However, the physical properties of only a few materials have been controlled by the electrostatic carrier-doping during the past decade. Here, we report an observation of superconductivity in a 2D layered material, LaOBiS2, achieved by the electrostatic electron-doping. The electron doping of LaOBiS2 induced metallic conductivity in the normally insulating LaOBiS2, ultimately led to superconductivity. The superconducting transition temperature, Tc, was 3.6 K, higher than the 2.7 K seen in LaO1-xFxBiS2 with an electron-doped BiS2 layer. A rapid drop in resistance (R) was observed at low temperature, which disappeared with the application of high magnetic fields, implying a superconducting state. This study reveals that electron-doping is an important technique for inducing superconductivity in 2D layered BiS2 materials.

  13. Synthesis, characterization and electrical properties of sol-gel derived 0.63Bi(Mg{sub 1/2}Ti{sub 1/2})O{sub 3}-0.37PbTiO{sub 3} high-T{sub c} piezoelectric ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Ji Xun [Institute of Electro Ceramics and Devices, School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Zuo Ruzhong, E-mail: piezolab@hfut.edu.cn [Institute of Electro Ceramics and Devices, School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Qi Shishun; Liu Longdong [Institute of Electro Ceramics and Devices, School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China)

    2012-06-15

    The nano-scaled powders of a high Curie temperature piezoelectric system with a composition of 0.63Bi(Mg{sub 1/2}Ti{sub 1/2})O{sub 3}-0.37PbTiO{sub 3} (0.63BMT-0.37PT) have been synthesized via a citrate sol-gel method. The thermal decomposition process of the as-prepared xerogel was investigated through the thermo-gravitometry and differential scanning calorimetry. The lattice structure of the powders as the function of heat-treatment temperatures was explored by using X-ray diffraction, Fourier-transform infra-red and Raman spectra. The results indicated that the transparent gel could be obtained via the chelate reaction of citric acid with ethylene glycol and ethanolamine assist. Gels can be transformed into crystallite powders with a single-phase perovskite structure when heat-treated at 600 Degree-Sign C for 3 h, much lower than that of traditional solid-state reaction method. The sol-gel derived 0.63BMT-0.37PT ceramics sintered at 1020 Degree-Sign C exhibit excellent dielectric, ferroelectric and piezoelectric properties of T{sub c} = 463 Degree-Sign C, {epsilon}{sub 33}{sup T}=1208, tan {delta} = 0.063, P{sub r} = 22.1 {mu}C cm{sup -2} and d{sub 33} = 230 pC N{sup -1}. Moreover, a small amount of Mn{sup 2+} doping could cause the reduced leakage current and slightly increased T{sub c} values. - Highlights: Black-Right-Pointing-Pointer We synthesize BMT-PT superfine powders of a high Curie temperature piezoelectric system of via citrate sol-gel method. Black-Right-Pointing-Pointer We characterize the powders by means of DSC, XRD, FT-IR, Raman and TEM. Black-Right-Pointing-Pointer Sol-gel derived BMT-PT ceramics sintered at 1020 Degree-Sign C exhibit optimum electrical properties.

  14. Processing of bulk Bi-2223 high-temperature superconductor

    Directory of Open Access Journals (Sweden)

    Alexander Polasek

    2005-12-01

    Full Text Available The Bi2Sr2Ca2Cu3 O10+x (Bi-2223 is one of the main high temperature superconductors for applications. One of these applications is the Superconductor Fault Current Limiter (SCFCL, which is a very promising high temperature superconducting device. SCFCL's can be improved by using bulk superconductors with high critical currents, which requires a sufficiently dense and textured material. In the present work, a process for improving the microstructure of Bi-2223 bulk samples is investigated. Pressed precursor blocks are processed by sintering with a further partial melting step, in order to enhance the Bi-2223 grain texture and to healing cracks induced by pressing. In order to improve the microstructure, the precursor is mixed with silver powder before pressing. Samples with and without silver powder have been studied, with the aim of investigating the influence of silver on the microstructure evolution. The phase contents and the microstructure obtained have been analyzed through XRD and SEM/EDS. The electromagnetic characterization has been performed by Magnetic Susceptibility Analysis. We present and discuss the process and the properties of the superconducting blocks. High fractions of textured Bi-2223 grains have been obtained.

  15. Superconducting cavities for LEP

    CERN Multimedia

    1983-01-01

    Above: a 350 MHz superconducting accelerating cavity in niobium of the type envisaged for accelerating electrons and positrons in later phases of LEP. Below: a small 1 GHz cavity used for investigating the surface problems of superconducting niobium. Albert Insomby stays on the right. See Annual Report 1983 p. 51.

  16. Academic training: Applied superconductivity

    CERN Multimedia

    2007-01-01

    LECTURE SERIES 17, 18, 19 January from 11.00 to 12.00 hrs Council Room, Bldg 503 Applied Superconductivity : Theory, superconducting Materials and applications E. PALMIERI/INFN, Padova, Italy When hearing about persistent currents recirculating for several years in a superconducting loop without any appreciable decay, one realizes that we are dealing with a phenomenon which in nature is the closest known to the perpetual motion. Zero resistivity and perfect diamagnetism in Mercury at 4.2 K, the breakthrough during 75 years of several hundreds of superconducting materials, the revolution of the "liquid Nitrogen superconductivity"; the discovery of still a binary compound becoming superconducting at 40 K and the subsequent re-exploration of the already known superconducting materials: Nature discloses drop by drop its intimate secrets and nobody can exclude that the last final surprise must still come. After an overview of phenomenology and basic theory of superconductivity, the lectures for this a...

  17. Graphene: Carbon's superconducting footprint

    Science.gov (United States)

    Vafek, Oskar

    2012-02-01

    Graphene exhibits many extraordinary properties, but superconductivity isn't one of them. Two theoretical studies suggest that by decorating the surface of graphene with the right species of dopant atoms, or by using ionic liquid gating, superconductivity could yet be induced.

  18. Analysis of Mechanical Stresses/Strains in Superconducting Wire

    Science.gov (United States)

    Barry, Matthew; Chen, Jingping; Zhai, Yuhu

    2016-10-01

    The optimization of superconducting magnet performance and development of high-field superconducting magnets will greatly impact the next generation of fusion devices. A successful magnet development, however, relies deeply on the understanding of superconducting materials. Among the numerous factors that impact a superconductor's performance, mechanical stress is the most important because of the extreme operation temperature and large electromagnetic forces. In this study, mechanical theory is used to calculate the stresses/strains in typical superconducting strands, which consist of a stabilizer, a barrier, a matrix and superconducting filaments. Both thermal loads and mechanical loads are included in the analysis to simulate operation conditions. Because this model simulates the typical architecture of major superconducting materials, such as Nb3Sn, MgB2, Bi-2212 etc., it provides a good overall picture for us to understand the behavior of these superconductors in terms of thermal and mechanical loads. This work was supported in part by the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists (WDTS) under the Science Undergraduate Laboratory Internship (SULI) program.

  19. Superconducting wind turbine generators

    DEFF Research Database (Denmark)

    Abrahamsen, Asger Bech; Mijatovic, Nenad; Seiler, Eugen

    2010-01-01

    We have examined the potential of 10 MW superconducting direct drive generators to enter the European offshore wind power market and estimated that the production of about 1200 superconducting turbines until 2030 would correspond to 10% of the EU offshore market. The expected properties of future...... offshore turbines of 8 and 10 MW have been determined from an up-scaling of an existing 5 MW turbine and the necessary properties of the superconducting drive train are discussed. We have found that the absence of the gear box is the main benefit and the reduced weight and size is secondary. However......, the main challenge of the superconducting direct drive technology is to prove that the reliability is superior to the alternative drive trains based on gearboxes or permanent magnets. A strategy of successive testing of superconducting direct drive trains in real wind turbines of 10 kW, 100 kW, 1 MW and 10...

  20. Pulsed laser deposition and characterisation of thin superconducting films

    Energy Technology Data Exchange (ETDEWEB)

    Morone, A. [CNR, zona industriale di Tito Scalo, Potenza (Italy). Istituto per i Materiali Speciali

    1996-09-01

    Same concepts on pulsed laser deposition of thin films will be discussed and same examples of high transition temperature (HTc) BiSrCaCuO (BISCO) and low transition temperature NbN/MgO/NbN multilayers will be presented. X-ray and others characterizations of these films will be reported and discussed. Electrical properties of superconducting thin films will be realized as a function of structural and morphological aspect.