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Sample records for ceramic superconducting bi

  1. Bi-Sr-Ca-Cu-O superconducting ceramics

    International Nuclear Information System (INIS)

    BiSrCaCu2Ox ceramic samples with a superconducting phase at 107K have been sinthesized. The critical temperature has been determined by Meissner effect measurements. That same 107K phase has also been detected in the following compounds: Bi2Sr2Ca2Cu3Ox and Bi3.6Sr2.7Ca2.7Cu2.7Cu4Ox. (author)

  2. Electrical and infrared comparative study of Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8/ in semiconducting, superconducting ceramic and superconducting glass ceramic state

    International Nuclear Information System (INIS)

    We have studied the electrical and infrared properties of Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub 8/ compound in three states. Electrical and IR measurements show that the pure powder state sample is a semiconductor, the ceramic Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub 8/ sample prepared after annealing at 820 C for 240 hours shows a T/sub c/ of 85 K, whereas Bi/sub 2/Sr sub 2/Ca/sub 1/Cu/sub 2/O/sub 8/ sample prepared through glassy route, i.e. melting at 1250 C and annealing at 820 C for 240 hours shows a drop of T/sub c/ by 5 K. The infrared spectra of superconducting ceramic and glass ceramic states in the available frequency range of measurement reveals the presence of three phonons. Since the vibrational mode around 595 cm/sup -1/ is due to CuO/sub 2/ layers and as the CuO/sub 2/ layers are responsible for T/sub c/ in the ceramic superconductors, any change in these layers will affect the T/sub c/. The shifting of the 595 cm/sup -1/ mode towards lower frequencies in the glass ceramic due to different preparation process indicates that there is a change in CuO/sub 2/ layers resulting in a change of T/sub c/, which is confirmed by four probe dc measurements. (author)

  3. 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.

  4. Correlation between normal and superconducting transport properties of Bi1.65Pb0.35Sr2Ca2Cu3O10+δ ceramic samples

    International Nuclear Information System (INIS)

    We have studied normal and superconducting transport properties of nearly single phase Bi1.65Pb0.35Sr2Ca2Cu3O10+δ (Bi-2223) ceramic samples. The samples were prepared from the same batch obtained by solid-state reaction method and pressed uniaxially at different compacting pressures ranging from 90 to 600 MPa before the last heat treatment. We have found by using magnetization versus applied magnetic field measurements, performed in powder samples, that both the lower critical field H clg ∼ 80 Oe and the full penetration field H* ∼ 135 Oe of grains at 77 K are similar in all samples. From electrical resistivity measurements as a function of temperature, we were able to separate contributions arising from both the grain misalignment and microstructural defects. The results suggest that the grain orientation and the connectivity between grains are improved with increasing compacting pressures. It was found that the superconducting critical current density in zero applied magnetic field J c(0) measured in our samples increases from 58 A/cm2 to 418 A/cm2. The normalized critical current density dependence on applied magnetic field, J c(B a)/J c(0), has showed to be very sensitive to the compacting pressure: it exhibits a clear Josephson-like behavior at low compacting pressure, which changes to a more magnetic field independent behavior at higher compacting pressures. In addition, the flux-trapping curves of samples subjected to different compacting pressure have revealed the presence of three superconducting levels: the superconducting grains, the superconducting clusters, and the weak links. A correlation between the normal and superconducting transport properties of these materials is discussed based on their dissipation mechanisms

  5. Influence of oxygen on the structural stability and superconducting properties of ceramic (Bi,Pb)2Sr2Ca2Cu3Oδ

    International Nuclear Information System (INIS)

    By post-annealing ceramic samples in various partial pressures of oxygen, the structural stability and superconducting properties of (Bi,Pb)2Sr2Ca2Cu3Oδ are demonstrated to be sensitive to δ. The small decrease of Tc with increasing oxygen partial pressure is in agreement with previously reported results on Pb-free samples and may be connected to an optimization of the charge carrier concentration. The collapse of the 2223 phase when post-annealed above 700 degree C in pure argon is also documented. It is suggested that this decomposition and the stabilization of the 2223 phase by Pb substitution are both related to the amount of oxygen contained in the (Bi,Pb)-O layers which separate the Sr-Ca-Cu-O perovskite units

  6. Thick highly textured (Bi, Pb)-2223 ceramics

    International Nuclear Information System (INIS)

    Dense (Bi, Pb)2Sr2Ca2Cu3O10+x ceramics textured by sinter-forging exhibit superconducting properties among the best for polycrystalline bulk 2223 materials. Investigations showed that the deformation during the sinter-forging process is mainly responsible for the grain alignment of the ceramics. A sharp texture can only be obtained after a strong deformation from the starting cold-pressed powder to the final thin forged disc. To obtain thick ceramics, several thin and highly identically textured discs were linked together by an additional short sinter-forging step. Microscopic observations showed that the interface between the discs disappeared after the hot treatment. Transport critical current measurements performed at 77 K through bars of different sizes confirm that, through an equal texture, the critical current density (JCT = 10,000 A cm-2) is nearly constant with the shape of the bar section: thin or thick, narrow or wide. A ceramic composed of many stacked and sinter-forged discs allowed resistivity and JCT to be measured along the sinter-forging axis. Low anisotropic ratios confirmed the strong link between the thin discs and a very homogeneous whole ceramic. This shape processing of bulk 2223 ceramics is thus attractive for the fabrication of current leads and limiters with high capabilities. (author)

  7. 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. PMID:25658139

  8. Growth structure and superconductivity of Bi1.7Bi0.3Sr2Ca2Cu3O10+δ ceramics synthesized from glass-crystal precursors processed in solar type ovens

    Science.gov (United States)

    Acrivos, J. V.; Gulamova, D. D.; Chigvinadze, J. G.; Loy, D.

    2010-03-01

    The growth structure as well as the superconductivity of Bi/Pb2223 alloys is reported. Periodic lattice distortions (PLD) along the ab plane diagonal, direction of superconducting transport at the transition temperature, Tc=107K are found to dominate the growth. Trransport induced by the PLD may be responsible for the sharp Tc transitions, and the bursts of frequency and Abrikosov oscillations observed above the transition temperature up to 150K. Chemical synthesis in a heliostat oven was followed by fast quenching of the melt and annealing at 840-850K, XRD near the Cu K-edge, and Tc measured by axial-torsional vibrations in transverse magnetic fields. Tc and phaase purity obtained by green solid state chemistry, in a solar spectrum, will be discussed.

  9. 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

  10. 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...

  11. 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.

  12. 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.

  13. Electrical resistivity measurements in superconducting ceramics

    International Nuclear Information System (INIS)

    Electrical resistivity measurements have been done in (Y, Ba, Cu, O) - and (Y, A1, Ba, Cu, O) - based superconducting ceramics. The sintered specimens were prepared by applying gold electrodes and winding on the non-metalized part with a copper strip to be immersed in liquid nitrogen for cooling. The resistivity measurements have been done by the four-probe method. A copper-constantan or chromel-alumel thermocouple inserted between the specimen and the copper cold finger has been used for the determination of the critical temperature Tc. Details of the experimental set-up and resistivity versus temperature plots in the LNT-RT range for the superconducting ceramics are the major contributions of this communication. (author)

  14. 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.

  15. Strong superconducting strength in ε-PbBi microcubes

    Science.gov (United States)

    Gandhi, Ashish Chhaganlal; Wu, Sheng Yun

    2016-06-01

    Single phase ε-PbBi microcubes were synthesized using a simple thermal evaporation method. Synchrotron x-ray measurement of the crystal structure of the ε-PbBi microcubes revealed a space group of P63/mmc. Enhanced superconducting transitions were observed from the temperature dependent magnetization, showing a main diamagnetic Meissner state below a TC of ~8.66(2) K. An extremely strong superconducting strength (α=2.51(1)) and electron-phonon constant (λEP=2.25) are obtained from the modified Allen and Dynes theory, which give rise to higher TC superconductivity in this type of structure. The electron-phonon coupling to low lying phonons is found to be the leading mechanism for the observed strong-coupling superconductivity in the PbBi system.

  16. 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.

  17. Effects of MgO and Al2O3 additions on the formation of the high Tc phase and superconducting properties in the Bi-Pb-Sr-Ca-Cu-O ceramic systems

    International Nuclear Information System (INIS)

    This paper reports on the effects of addition of different amounts of MgO and Al2O3 to the starting composition of BPSCCO ceramic superconductors that have been analyzed by means of X-ray diffraction, magnetic measurements, SE and EDS. The results show that the superconducting properties of BPSCC are not directly influenced by the addition. The presence of Al2O3 induces, however, the formation of a new Al-rich paramagnetic phase which modifies the effective starting stoichiometry increasing sample contamination by copper oxide and calcium cuprate

  18. Mass spectrometric analysis of laser evaporation products of ceramics of Bi2Sr2CaCu2Ox composition

    International Nuclear Information System (INIS)

    Mass spectrometric analysis is used to study mechanism of laser evaporation of superconducting ceramics of Bi2Sr2CaCu2Ox composition. During evaporation as a result of pulsed laser irradiation of a sample placed in vaccum ions of all metals containing in ceramics and also neutral O2, Ca, Sr, Cu, Bi and metal oxides were detected on yttrium aluminate. Time-of-flight spectra had two peaks corresponding to ion and neutral components. Comparison of neutral components. Comparison of neutral particle rates points to the fact that gas dynamic processes connected with formation of dense gas cloud near the target surface play an important

  19. Superconductivity in BiO1−xFxBiS2 and possible parent phase of Bi4O4S3 superconductor

    International Nuclear Information System (INIS)

    We report the discovery of superconductivity in BiO1−xFxBiS2, an isostructural compound of the REO1−xFxBiS2 (RE: La, Nd, Pr, Ce, and Yb) superconductors. The parent compound, Bi2OS2, is nonsuperconductive. Superconductivity is observed in a wide range of F-doping content (0.06 ⩽ x ⩽ 0.27). The optimal F-doping concentration is about 0.24 in BiO1−xFxBiS2, where the highest transition temperature of 3.5 K is achieved. We suppose that the superconductivity in BiO1−xFxBiS2, as well as that in Bi3O2S3 and Bi4O4S3, is induced by partial substitution or insertion in the Bi2OS2 parent phase. (paper)

  20. Superconducting properties and electronic structure of NaBi.

    Science.gov (United States)

    Kushwaha, S K; Krizan, J W; Xiong, J; Klimczuk, T; Gibson, Q D; Liang, T; Ong, N P; Cava, R J

    2014-05-28

    Resistivity, dc magnetization, and heat capacity measurements are reported for superconducting NaBi. T(c), the electronic contribution to the specific heat γ, the ΔC(p)/γT(c) ratio, and the Debye temperature are found to be 2.15 K, 3.4 mJ mol(-1) K(-2), 0.78, and 140 K respectively. The calculated electron-phonon coupling constant (λ(ep) = 0.62) implies that NaBi is a moderately coupled superconductor. The upper critical field and coherence length are found to be 250 Oe and 115 nm, respectively. Electronic structure calculations show NaBi to be a good metal, in agreement with the experiments; the p(x) and p(y) orbitals of Bi dominate the electronic states at the Fermi Energy. PMID:24804822

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

    OpenAIRE

    SUN TING, BDS, DDS; SHAO LONQUAN, DDS, MS; DENG BIN, DDS, MS; WEN NING, DDS, MS

    2012-01-01

    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 ther...

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Transport properties of the superconducting Bi2Sr2Ca2Cu3O10-DyBa2SnO5.5 percolation system

    International Nuclear Information System (INIS)

    Electrical transport properties and percolation behavior of superconducting Bi2Sr2Ca2Cu3O10-DyBa2SnO5.5, a superconductor-insulator composite system, have been studied by x-ray diffraction and temperature-resistivity measurements. Normal-state and superconducting percolation threshold values are found to be ∼20 vol % of Bi(2223) in the composite. The values obtained for critical exponents describing the normal-state transport behavior of the system are matched with theoretically expected values for an idealized metal-insulator composite system. No detectable chemical reactivity was observed between Bi(2223) and the ceramic insulator DyBa2SnO5.5, even under severe heat treatment at 850 degree C. The implications are discussed

  8. Studies of the bulk orientation in Y and Bi superconducting phases

    International Nuclear Information System (INIS)

    We present here some of our studies on the bulk orientation of the grains in the Y superconductor with various experimental techniques and also the first results of Bi superconducting phases. (orig./BHO)

  9. 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.

  10. 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.)

  11. 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.

  12. A study on the superconducting phases of the Bi-Sr-Ca-Cu-O system

    International Nuclear Information System (INIS)

    In this paper a preparation technique of superconducting Bi-Sr-Ca-Cu-O phases starting from amorphous matrices of composition 1:1:1:2 and 2:2:2:3 is described. DTA, TGA, XRD and Tc resistive measurements are reported. The competitive growth of different superconducting phases is discussed

  13. Superconducting oxide processing in the Bi-Ca-Sr-Cu-O system

    International Nuclear Information System (INIS)

    This paper reports microstructures of superconducting phase with transitions near 85 K and 110 K studied by analytical electron microscopy (AEM) in samples of the system Bi-Ca-Sr-Cu-O prepared by sintering and liquid mixing methods. The heat treatment was restricted to a temperature range near 860 degrees C to obtain good superconducting behavior. The microchemistry and the crystal structure of the superconducting phase in the Bi-Ca-Sr-Cu-O system were investigated by energy dispersive x-ray spectroscopy and convergent-beam electron diffraction, and were related to the processing routes

  14. A study on the Joining Properties of Bi-2212 High-Tc Superconducting Tube and Indium Solder

    International Nuclear Information System (INIS)

    As a material for SFCL(Superconducting Fault Current Limiter), BSCCO tube with metal stabilizer is a promising candidate, assuring the stability and large power capacity, For the application, the proper soldering technique, which overcome the difficulties of the joining between BSCCO and metal stabilizer, is required. In this study, after soldering In-Bi solder and In-Sn solder with BSCCO superconductor, welding properties between BSCCO and solders were investigated. Because ceramic materials is difficult to weld, Ag electro-plating on BSCCO 2212 is used for intermetallic layer. To find out the best welding condition for superconductor, soldering is tested in the maximum temperature from 155 degrees C to 165 degrees C in the reflow oven. By investigating the composition and thickness of IMC (lntermetallic Compound) created in the reaction of Ag with solder, we analyzed the welding properties of High-Tc superconductor from a micro point of view.

  15. Ferroelectric properties of BiFeO3 ceramics sintered under low oxygen partial pressure

    International Nuclear Information System (INIS)

    BiFeO3 ceramics were prepared in various atmospheres with hydrothermally-synthesized BiFeO3 crystalline powders, and their dielectric and ferroelectric properties were investigated. The single BiFeO3 phase was formed when the sample was sintered at 800 .deg. C under air, and a minor Bi2Fe4O9 phase was observed when it was sintered under a N2 or an Ar atmosphere. The BiFeO3 ceramic sintered under N2 showed a dense microstructure and superior electric properties: a dielectric constant of 75, a low loss tangent of 0.01 at 100 kHz and a high resistivity of 1.37 x 1011 Ω · cm. A pinched and asymmetric P-E hysteresis and a typical butterfly-shaped S-E loop were observed in the BiFeO3 ceramic sintered under N2. The electric properties of BiFeO3 ceramics sintered in various atmospheres are discussed on the basis of defect chemistry.

  16. 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.

  17. Disparity of superconducting and pseudogap scales in low-Tc Bi-2201 cuprates

    OpenAIRE

    Jacobs, Th.; Katterwe, S. O.; Motzkau, H.; Rydh, A.; Maljuk, A.; Helm, T.; Putzke, C.; Kampert, E.; Kartsovnik, M. V.; Krasnov, V. M.

    2012-01-01

    We experimentally study transport and intrinsic tunneling characteristics of a single-layer cuprate Bi(2+x)Sr(2-y)CuO(6+delta) with a low superconducting critical temperature Tc < 4 K. It is observed that the superconducting energy, critical field and fluctuation temperature range are scaling down with Tc, while the corresponding pseudogap characteristics have the same order of magnitude as for high-Tc cuprates with 20 to 30 times higher Tc. The observed disparity of the superconducting and p...

  18. Effect of oxygen partial pressure on the superconductivity of Bi-2212 wires during post-annealing

    International Nuclear Information System (INIS)

    The effect of PO2 on Bi-2212 wires was studied which is crucial for HTS applications. PO2 dependence of c value of Bi-2212 wires is different from Bi-2212 tapes. Bi-2212 lattice changes from orthorhombic to tetragonal with increasing PO2. Cu-O chains will break if the PO2 is too low, which will lead to the decrease of Jc. Bi2Sr2CaCu2O8+δ (Bi-2212) silver sheathed round wire is a promising and practical material for high field superconducting insert magnet in the range of 25-30 T. The effect of oxygen content of Bi-2212 on the critical current density (Jc) of multi-filamentary Bi-2212/Ag wires has been investigated. During the Bi-2212 wire fabrication, partial melting and solidification process was employed. Short samples which were cut from the same wire were annealed at 500 deg. C in various atmospheres for post-annealing. The morphology, lattice parameters and oxygen contents were characterized by SEM, XRD and a thermal gravimetric analyzer (TGA). The critical current (Ic) and the superconducting transition temperature (Tc) were measured by a four-probe method. Lower O2 pressure can break the Bi-O chains, reduce the oxygen contents and change the lattice structure of Bi-2212 from tetragonal into orthorhombic. The Tc values of samples increase from 81.6 K to 91 K and the highest Jc of samples after post-annealing is almost three times higher than that of the initial sample.

  19. Dielectric properties and phase transitions of BiNbO4 ceramic

    International Nuclear Information System (INIS)

    In the present work, HP-BiNbO4 was found, by in situ X-ray diffraction, thermal expansion and differential thermal analysis, to transform to orthorhombic BiNbO4 at around 680 °C along with an abrupt increase of volume, and to then transform to the triclinic BiNbO4 at around 1000 °C with an endothermic phenomenon. The results indicate that the dielectric permittivity of HP-BiNbO4 ceramic prepared via the high-temperature/high-pressure method was increased remarkably and this might work in other dielectric systems

  20. Fully gapped superconductivity in the topological superconductor β -PdBi2

    Science.gov (United States)

    Biswas, P. K.; Mazzone, D. G.; Sibille, R.; Pomjakushina, E.; Conder, K.; Luetkens, H.; Baines, C.; Gavilano, J. L.; Kenzelmann, M.; Amato, A.; Morenzoni, E.

    2016-06-01

    The recent discovery of the topologically protected surface states in the β phase of PdBi2 has reignited the research interest in this class of superconductors. Here, we show results of our muon spin relaxation and rotation (μ SR ) measurements carried out to investigate the superconducting and magnetic properties and the topological effect in the superconducting ground state of β -PdBi2 . Zero-field μ SR data reveal that no sizable spontaneous magnetization arises with the onset of superconductivity implying that the time reversal symmetry is preserved in the superconducting state of β -PdBi2 . Further, a strong diamagnetic shift of the applied field has been observed in the transverse-field (TF) μ SR experiments, indicating that any triplet-pairing channel, if present, does not dominate the superconducting condensate. Using TF-μ SR , we estimate that the magnetic penetration depth λ =263 (10 ) nm at zero temperature. The nature of λ (T ) provides evidence for the existence of a nodeless single s -wave type isotropic energy gap of 0.78(1) meV at zero temperature. Our results further suggest that the topologically protected surface states have no effect on the bulk of the superconductor.

  1. An investigation of the element composition of superconducting ceramics by neutron activation and radiography methods

    International Nuclear Information System (INIS)

    The neutron activation methods for determining the general composition and distribution of the main components in HTSC ceramics were developed. The conditions for the reduction of the analysis error were discussed. The dependences of the oxygen content and superconducting parameters of single-phase and polyphase yttrium ceramics on the regime of heat treatment in air were investigated. Variation in the oxygen content was found to have a nonmonotone character, depending on the temperature of quenching and annealing. Correlation between the character of the superconducting transition and the oxygen content was observed. During the heat treatment, reversible structural phase transitions proceed in the single-phase ceramics in the polyphase ceramics, the recrystallization processes occur, which result in homogenization of its structure

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Soldering of Bi-2223/Ag high temperature superconducting tapes with Sn-Pb-Bi-Ag alloy paste

    Science.gov (United States)

    Wei, Guo; Guisheng, Zou; Aiping, Wu; Hailin, Bai; Jialie, Ren

    2010-01-01

    Soldered joints of Bi-2223/Ag-sheathed high temperature superconducting multifilamentary tapes were fabricated using 63 wt.%Sn-34 wt.%Pb-1 wt.%Bi-2 wt.%Ag paste. The soldered joints were observed by scanning electron microscope (SEM) and X-ray diffraction (XRD). Moreover, the electrical properties of joints were evaluated by current-voltage curves, and the tensile strengths of the joints were also tested. The results show that the soldered joint consists of Ag sheath - Ag 3Sn compound layer - PbSn 2 and Ag 3Sn solder layer - Ag 3Sn compound layer - Ag sheath. The joints are obeyed with Ohms Law and the magnitude of the joint resistance, which deceases with the increase of the overlap length, can reach the order of 10 -8 Ω. The tensile strength of the joints with a brittle fracture mode is a little lower than that of the original tapes.

  7. Enhanced broadband near-infrared luminescence from Ni in Bi/Ni-doped transparent glass ceramics

    International Nuclear Information System (INIS)

    Spectral properties of Bi/Ni-doped transparent MgO-Al2O3-Ga2O3-SiO2-TiO2 glass ceramics (GCs) containing spinel solution nanocrystals were investigated. The emission intensity of Ni in Bi/Ni-doped GCs was about 4 times stronger than that of Ni-doped GCs due to energy transfer from Bi to Ni. The Bi/Ni-doped GCs with 0.75 mol% Bi2O3 concentration exhibited a near-infrared emission with full width at half maximum of about 270 nm and a fluorescent lifetime of about 350 μs, making them very promising for applications in broadband optical amplifiers and tunable lasers.

  8. Enhanced broadband near-infrared luminescence from Ni in Bi/Ni-doped transparent glass ceramics

    Science.gov (United States)

    Wu, Botao; Ruan, Jian; Qiu, Jianrong; Zeng, Heping

    2009-07-01

    Spectral properties of Bi/Ni-doped transparent MgO-Al2O3-Ga2O3-SiO2-TiO2 glass ceramics (GCs) containing spinel solution nanocrystals were investigated. The emission intensity of Ni in Bi/Ni-doped GCs was about 4 times stronger than that of Ni-doped GCs due to energy transfer from Bi to Ni. The Bi/Ni-doped GCs with 0.75 mol% Bi2O3 concentration exhibited a near-infrared emission with full width at half maximum of about 270 nm and a fluorescent lifetime of about 350 µs, making them very promising for applications in broadband optical amplifiers and tunable lasers.

  9. Enhanced broadband near-infrared luminescence from Ni in Bi/Ni-doped transparent glass ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Wu Botao; Zeng Heping [State Key Laboratory of Precision Spectroscopy and Department of Physics, East China Normal University, Shanghai 200062 (China); Ruan Jian [Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China) and Graduate School of the Chinese Academy of Sciences, Beijing 100039 (China); Qiu Jianrong, E-mail: botao.wu@yahoo.com.c [State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027 (China)

    2009-07-07

    Spectral properties of Bi/Ni-doped transparent MgO-Al{sub 2}O{sub 3}-Ga{sub 2}O{sub 3}-SiO{sub 2}-TiO{sub 2} glass ceramics (GCs) containing spinel solution nanocrystals were investigated. The emission intensity of Ni in Bi/Ni-doped GCs was about 4 times stronger than that of Ni-doped GCs due to energy transfer from Bi to Ni. The Bi/Ni-doped GCs with 0.75 mol% Bi{sub 2}O{sub 3} concentration exhibited a near-infrared emission with full width at half maximum of about 270 nm and a fluorescent lifetime of about 350 mus, making them very promising for applications in broadband optical amplifiers and tunable lasers.

  10. 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.

  11. Electronic structure of a superconducting topological insulator Sr-doped Bi2Se3

    International Nuclear Information System (INIS)

    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 (SrxBi2Se3) 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 Bi2Se3, 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

  12. 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.

  13. Superconductivity:

    Science.gov (United States)

    Sacchetti, N.

    In this paper a short historical account of the discovery of superconductivity and of its gradual development is given. The physical interpretation of its various aspects took about forty years (from 1911 to 1957) to reach a successful description of this phenomenon in terms of a microscopic theory At the very end it seemed that more or less everything could be reasonably interpreted even if modifications and refinements of the original theory were necessary. In 1986 the situation changed abruptly when a cautious but revolutionary paper appeared showing that superconductivity was found in certain ceramic oxides at temperatures above those up to then known. A rush of frantic experimental activity started world-wide and in less than one year it was shown that superconductivity is a much more widespread phenomenon than deemed before and can be found at temperatures well above the liquid air boiling point. The complexity and the number of the substances (mainly ceramic oxides) involved call for a sort of modern alchemy if compounds with the best superconducting properties are to be manufactured. We don't use the word alchemy in a deprecatory sense but just to emphasise that till now nobody can say why these compounds are what they are: superconductors.

  14. Optimization of the 120 K superconducting phase in the BiSrCaCuO system

    International Nuclear Information System (INIS)

    The formation of the 120 K superconducting phase in the BiSrCaCu2Oy system has been investigated by microwave absorption. This material is characterized by an intense, low-field microwave absorption (LFMA) below the superconducting transition temperature Tc and a g = 2 electron spin resonance (ESR) signal above Tc. The LFMA is used to follow the formation of the high Tc phases in this compound. The purity of these superconducting phases is also reflected by the intensity of the g = 2 signal. Various stages of sample preparation are studied to optimize the reaction conditions for the formation of the 120 K phase. LFMA and ESR results are also compared and contrasted with resistance measurements

  15. Interplay between the pseudogap, mode coupling and superconductivity in Bi-based cuprates

    Science.gov (United States)

    Hashimoto, Makoto

    2013-03-01

    Complexity of the high-Tc cuprate superconductors is partly due to the coexisting energy scales that are of the order of superconducting gap (commencement of the pseudogap state at temperature T* using three different techniques (ARPES, polar Kerr effect, and Time-resolved reflectivity) on the same optimally doped Bi2201 crystals. The result suggests that the pseudogap is a disinct phase that shows broken symmetry,[2,3] which could be consistent with the two-dimentional charge ordering observed by STM and scattering measurements. Further, we discuss how this distinct pseudogap order is entangled with superconductivity below Tc. In Bi2212, by analyzing the ARPES spectral weihgt in the antinodal region, we show compelling evidence for the dynamic competition between the two order parameters for the pseudogap and superconductivity as a function of temperature.[4] Such competition can naturally result in the shift of the critical point for the pseudogap.[5] Moreover, by studying the detailed temperature and doping dependence of the spectral lineshape in the antinodal region, we reveal that the interplay between the pseudogap, bosonic-mode coupling and superconductivity with similar energy scales is crucial and they have to be considered in a integrated picture to understand the cuprates electronic structure.[6]*These authors equally contributed to the work. This work is supported by the Department of Energy, Office of Basic Energy Science, Division of Materials Science.

  16. Analysis of flat rolling of superconducting silver/ceramic composites

    DEFF Research Database (Denmark)

    Bech, Jakob Ilsted; Nielsen, Morten Storgård; Eriksen, Morten;

    2001-01-01

    The flat rolling process from wire to tape is presumably the most crucial link in the chain of mechanical processes leading from loose powder and silver tubes to the final superconducting Ag/BSCCO tape. In order to improve the critical current density of the superconducting filaments, one must...... process these to the highest possible density without at the same time introducing failures as large cracks and macroscopic shear bands. In order to analyse and optimise the process, the interaction between the involved materials and their very different mechanical properties must be taken into account...

  17. 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.

  18. 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.

  19. Pressure-induced reemergence of superconductivity in topological insulator Sr0.065Bi2Se3

    Science.gov (United States)

    Zhou, Yonghui; Chen, Xuliang; Zhang, Ranran; Shao, Jifeng; Wang, Xuefei; An, Chao; Zhou, Ying; Park, Changyong; Tong, Wei; Pi, Li; Yang, Zhaorong; Zhang, Changjin; Zhang, Yuheng

    2016-04-01

    The recently discovered SrxBi2Se3 superconductor provides an alternative and ideal material base for investigating possible topological superconductivity. Here, we report that in Sr0.065Bi2Se3 , the ambient superconducting phase is gradually depressed upon the application of external pressure. At high pressure, a second superconducting phase emerges at above 6 GPa, with a maximum Tc value of ˜8.3 K. The joint investigations of the high-pressure synchrotron x-ray diffraction and electrical transport properties reveal that the reemergence of superconductivity in Sr0.065Bi2Se3 is closely related to the structural phase transition from an ambient rhombohedral phase to a high-pressure monoclinic phase around 6 GPa, and further to another high-pressure tetragonal phase above 25 GPa.

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Assessment of strain of Bi2223 filaments in bent Ag-sheathed superconducting composites by synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Okuda, Hiroshi [International Innovation Center, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan); Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501 (Japan)], E-mail: okuda@materials.mbox.media.kyoto-u.ac.jp; Shin, Jae-Kyong; Iwamoto, Sohei [Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501 (Japan); Morishita, Kohei [International Innovation Center, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan); Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501 (Japan); Mukai, Yasuhiro; Matsubayashi, Hiroshi [Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501 (Japan); Ochiai, Shojiro [International Innovation Center, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan); Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501 (Japan); Otto, Alex; Harley, Edward J.; Malozemoff, Alexis P. [American Superconductor Inc, 2 Technology Drive, Westborough, MA 01581 (United States); Sato, Masugu [Japan Synchrotron Radiation Research Institute, JASRI Sayo, Hyogo (Japan)

    2008-04-15

    The bending strains of Bi2223 filaments in Ag-sheathed superconducting composite tapes at the Bi2223/Ag sheath boundary have been evaluated by X-ray diffraction utilizing synchrotron radiation at room temperature. The strain in the Bi2223 filaments was found to be asymmetric between the sides under tension and compression, suggesting that the fracture strain is also asymmetric between tension and compression. The outermost part of the Bi2223 filaments is at the multiple fracture stage in the tension side.

  6. Comparison of irreversibility lines of silver-sheathed Bi-2223, Tl-1223 and Tl-1234 superconducting tapes

    International Nuclear Information System (INIS)

    The irreversibility lines of silver-sheathed (Bi,Pb)2Sr2Ca2Cu3O10 (Bi-2223), (Tl,Pb,Bi)(Sr,Ba)2Ca2Cu3O9(Tl-1223) and (Tl,Pb)Sr2Ca3Cu4O11 (Tl-1234) superconducting tapes were investigated and compared with those of other superconducting systems. We have demonstrated that the shape of the irreversibility lines of Tl-1223 and Tl-1234 superconducting tapes are similar in behavior to those of YBa2Cu3O7 (Y-123) and (Tl,Pb)Sr2(Ca,Y)Cu2O7 (Tl-1212) systems and better than those of Tl2Ba2Ca2Cu3O10 (Tl-2223) and (Bi,Pb)2Sr2Ca2Cu3O10 (Bi-2223) superconductors. This means that the flux pinning ability of Tl-1223 and Tl-1234 superconducting tapes was stronger than that of Bi-2223 and Tl-2223 superconductors. The possible reason for controlling flux pinning can be attributed to the intrinsic crystal structure difference in the materials. (orig.)

  7. Superconducting Bi-Ca-Sr-Cu oxide thin films by spray pyrolysis of metal acetates

    International Nuclear Information System (INIS)

    Superconducting Bi-Ca-Sr-Cu oxide thin films have been prepared on ZrO2-coated silicon (111) wafers by spray pyrolysis of metal acetate precursors followed by rapid annealing to 850 0C in air. Resistivity measurements indicate a broad superconducting transition with T/sub c/ onset near 90 K and zero resistivity below 60 K. The films are highly oriented with the c axis normal to the substrate surface and can be indexed to a tetragonal structure with lattice parameters of a = 3.832(1) A and c = 30.78(5) A. Both x-ray photoelectron spectroscopy and x-ray diffraction measurements indicate the loss of Ca to the ZrO2 buffer layer

  8. Bending deformation and its influence on critical current in Bi2223 composite superconducting tapes

    Energy Technology Data Exchange (ETDEWEB)

    Hojo, M.; Matsuoka, T.; Nakaoka, S.; Tanaka, M.; Ochiai, S.; Sugano, M.; Osamura, K

    2003-10-15

    The strain dependence of the critical current, I{sub c}, of Ag and Ag-alloy sheathed Bi2223 composite superconducting tapes has been studied under bending deformation. The tensile stress-strain behavior of the composite tapes was first analyzed to determine several unknown parameters such as Young's modulus, yield strength and the thermal expansion coefficients of each component. In this analysis, these were inversely decided to meet the global tensile stress-strain behavior including intermediate unloading and reloading processes and the thermal expansion of the composite tapes. Thus evaluated values were used for the bending analysis in which the movement of the neutral axis was taken into account. Based on the analyzed strain distribution, the relative decrease of the critical current with the increase of the Bi2223 tape curvature was calculated from the volume fraction of the broken filaments. The calculated value agreed well with the experimental results.

  9. 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-temperature...... superconducting tape, there will be large ac losses when the magnet is ramped up and down. An accurate estimation of the total ac losses in the high-temperature superconducting coils is essential for the cryogenic system design. In the Bi-2223/Ag coils, the total ac losses mainly originate from two parts: One...... is transport loss caused by the variation of transport current with respect to time, and the other is magnetization loss due to alternating external magnetic field. In this paper, the effect of temperature variation on ac losses generated in the Bi-2223/Ag coils is studied. The magnetic field and temperature...

  10. Superconducting tape characterization under flexion

    Science.gov (United States)

    Álvarez, A.; Suárez, P.; Cáceres, D.; Pérez, B.; Cordero, E.; Castaño, A.

    2002-08-01

    Electrotechnical applications of high temperature superconducting materials are limited by the difficulty of constructing classical windings with ceramic materials. While Bi-2223 tape may be a solution, it cannot be bent to radii less than a certain value since its superconducting capacity disappears. We describe an automated measurement system of the characteristics of this tape under flexion. It consists of a device that coils the tape over cylinders with different radii. At the same time, the parameters of its superconducting behaviour (e.g. resistance) are taken and processed. This system was developed at the “Benito Mahedero Laboratory of Superconducting Electrical Applications” in the University of Extremadura.

  11. 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.

  12. In situ synchrotron-radiation measurements of axial strain in laminated Bi2223 superconducting composite tapes at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Okuda, H. [International Innovation Center, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan)]. E-mail: okuda@iic.kyoto-u.ac.jp; Rokkaku, H. [Graduate School of Materials Science and Engineering, Kyoto University, Kyoto 606-8501 (Japan); Morishita, K. [Graduate School of Materials Science and Engineering, Kyoto University, Kyoto 606-8501 (Japan); Shin, J.K. [Graduate School of Materials Science and Engineering, Kyoto University, Kyoto 606-8501 (Japan); Iwamoto, S. [Graduate School of Materials Science and Engineering, Kyoto University, Kyoto 606-8501 (Japan); Ochiai, S. [International Innovation Center, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan); Sato, M. [Japan Synchrotron-Radiation Research Institute (JASRI), Kohto, Sayo 679-5198 (Japan); Osamura, K. [Graduate School of Materials Science and Engineering, Kyoto University, Kyoto 606-8501 (Japan); Otto, A. [American Superconductor Co. Ltd., 2 Technology Drive, Westborough, MA 01581 (United States); Harley, E.J. [American Superconductor Co. Ltd., 2 Technology Drive, Westborough, MA 01581 (United States); Malozemoff, A. [American Superconductor Co. Ltd., 2 Technology Drive, Westborough, MA 01581 (United States)

    2006-10-15

    Axial strain of Bi2223 superconducting filaments in Ag-sheathed superconducting composites reinforced by stainless steel lamination has been evaluated by in situ synchrotron-radiation diffraction. The Bi2223 filaments in the laminated composites were under 0.11% of compressive residual strain, whereas the residual strain of filaments in the composite after removing stainless steel layers was only 0.02% in compression. Under large tensile load, the composite showed a clear multiple fracture with an almost constant filament strain of about 0.11% in tension.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Strain effects on the AC critical current of Bi-2223 superconducting tapes

    International Nuclear Information System (INIS)

    Axial tensile strains effects on the AC critical current of Bi-2223/Ag and Bi-2223/AgMn tapes produced by the powder-in-tube method have been studied, at 77 K. 5 μV/cm field criterion was used to determine the AC and DC critical current. The degradation of AC critical current due to axial tensile strain is irreversible, the normalized AC and DC critical current Icn vs tensile strain ε curves Icn(ε) of Ag and AgMn/Ag sheathed Bi-2223 superconducting composite tapes are almost the same when the axial tensile strain is less than ε0.9, when the axial tensile strain is larger than ε0.9, the AC critical current Icn decrease less rapidly than DC critical current Icn, and at the same strain, the normalized AC critical current is greater than normalized DC critical current. This may be due to the greater relative increment in DC voltage than in AC voltage when the strain is large enough to deteriorate the transport capacity of the tape. The AC and DC Icn(ε) curves have the same empirical formula as Icn=1-(ε/a)b, where a and b are constants

  18. 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.

  19. Investigation of high voltage discharges in low pressure gases through large ceramic superconducting electrodes

    OpenAIRE

    Podkletnov, Evgeny; Modanese, Giovanni

    2002-01-01

    A device has been built and tested, in which a ceramic superconducting cathode and a copper anode cause electrical discharges in low pressure gases, at temperatures between 50 and 70 K. The electrodes are connected to a capacitors array charged up to 2000 kV; peak currents are of the order of 10^4 A. The cathode has the diameter of 10 cm and is fabricated by OCMTG technology. In discharges at voltage above 500 kV two new phenomena were observed, probably related to each other. First, the disc...

  20. 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.

  1. 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.

  2. 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.

  3. 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...

  4. 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.

  5. 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.

  6. Superconducting thin films of Bi-Sr-Ca-Cu-O by laser ablation

    International Nuclear Information System (INIS)

    The discovery of a new class of copper oxide superconductors has led to the development of three major systems that exhibit superconducting properties. The Bi-Sr-Ca-Cu-O superconductors offer intrinsic advantages due to the high Tc, chemical inertness and tolerance for a range of compositions. However, thin film research on these materials has progressed more slowly than the other cuprate systems. This dissertation examines the film growth, by laser ablation, of the Bi-Sr-Ca-Cu-O superconductors and the effect of the deposition parameters such as the laser target interaction, substrate temperature, target to substrate distance, deposition and cooling pressure, target type and processing and the substrate type. CO2 laser ablation was shown to give rise to a non-stoichiometric material transfer due to the low fluences and long pulse lengths. In situ superconducting thin films with Tc(0)'s of 76 K could be deposited using the KrF laser at substrate temperatures of 5 degrees C to 20 degrees C below phases. Lower temperatures gave rise to a mixture of 2201 and glassy phases. An increase in the target to substrate distance led to a deterioration of the electrical and structural properties of the films due to a decrease in the energy for film formation. A maximum in Tc(0) was observed at 450 mtorr as the deposition pressure was varied between 200 to 700 mtorr. Optimum oxygen incorporation could be achieved by cooling the films in high oxygen pressures and the best films were obtained with 700 torr cooling pressure. The oxygen deficiency of the hot pressed targets led to inferior properties compared to the conventionally sintered targets. The microwave surface resistance of the films measured at 35 GHz showed an onset at 80 K and dropped below that of copper at 30 K. The study of the laser ablation process in this system revealed the presence of a stoichiometric forward directed component and a diffuse evaporation component

  7. Synthesis, Structural and Electrical properties of Bi4Ti3O12 & Bi3.5La0.5Ti3O12 Ferroelectric ceramics

    Science.gov (United States)

    Roy, M.; Bala, Indu; Barbar, S. K.; Jangid, S.; Dave, P.

    2011-07-01

    Polycrystalline ceramic samples of Bi4Ti3O12 and the La-doped Bi3.5La0.5Ti3O12 have been synthesized by standard high temperature solid state reaction method using high purity oxides and carbonates. The effect of lanthanum doping on the structure of Bi4Ti3O12 powders was investigated by X-ray diffraction. A better agreement between the observed and calculated X-Ray diffraction pattern was obtained by performing the Rietveld refinement with a structural model using the non centrosymmetric space group Fmmm. Rietveld analysis revealed that with the partial substitution of La on the Bi site increases the a and b lattice parameters and decreases the c parameter. The activation energies calculated from dc conductivities are 1.033 eV and 2.244 eV which shows that La doping increases the resistivity of the material useful for dielectric devices.

  8. Phase characteristics of 0.92Bi0.5Na0.5TiO3-0.08BiAlO3 ceramics

    International Nuclear Information System (INIS)

    The phase characteristics of 0.92Bi0.5Na0.5TiO3-0.08BiAlO3 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 Td. 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 Td 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 0.92Bi0.5Na0.5TiO3-0.08BiAlO3 ceramics but also they may be helpful for further investigation on lead-free ceramics

  9. Growth of superconducting Bi 2Sr 2CaCu 2O 8+ δ(Bi-2212) single crystal whiskers and the characteristics

    Science.gov (United States)

    Oh, S.-Y.; Kim, S.-J.; Kim, G.-S.; Nagao, M.; Hatano, T.

    2006-10-01

    We have succeeded in the growth of superconducting Bi2Sr2CaCu2O8+δ(Bi-2212) single crystal whiskers with a Te-doped method. We use a Te-doped precursor with the mixed pure powders Bi2O3, SrCO3, CaCO3, CuO and TeO2 into the ratios of Bi2Sr2Ca2Cu2.5Te0.5Ox. Bi-2212 single crystal whiskers have grown through the pellet surface 2-4 mm in length and 20-100 μm in width. Characteristics of whiskers were investigated by the resistance-temperature (R-T), X-ray diffraction (XRD) and current-voltage (I-V) measurements. The R-T characteristics in ab-plane of the whiskers showed that their Tc,on and Tc,end were about 106 K and 75 K, respectively and confirmed that the whiskers had Bi-2212 single crystal phase by XRD pattern. The I-V curves showed multi-branch structures of intrinsic Josephson junctions (IJJ) as evidence of c-axis transport characteristics.

  10. 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.

  11. Quantitative description of the phase transition of Aurivillius oxides Sm modified BaBi4Ti4O15 ceramics

    Science.gov (United States)

    Fang, Pinyang; Liu, Peng; Xi, Zengzhe

    2015-07-01

    BaBi4Ti4O15+xwt.%Sm2O3 (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.

  12. Thermal annealing study of high-Tc YBaCuO and BiSrCaCuO superconducting wires

    International Nuclear Information System (INIS)

    High-Tc YBaCuO and BiSrCaCuO Superconducting wires have been fabricated by powder metallurgy technique. Copper and silver tubes were used as the external jackets. Thermal annealing treatments for all the wire-type samples were performed between 773 K and 1223 K. Both electrical and magnetization studies show that the superconducting properties can be improved after properly thermal annealing these samples with silver jacket. Our experimental results show that proper thermal annealing treatment can enhance the intragrain critical current density more than 100 times; however, the intergrain critical current density improves only a few times

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Evidence for phonon-mediated coupling in superconducting Ba sub 1-x K sub x BiO sub 3

    Energy Technology Data Exchange (ETDEWEB)

    Hinks, D.G.; Dabrowski, B.; Richards, D.R.; Jorgensen, J.D.; Pei Shiyou (Materials Science Div., Argonne National Lab., IL (USA)); Zasadzinski, J.F. (Illinois Inst. of Tech., Physics Dept., Chicago (USA))

    1989-12-01

    Superconducting Ba{sub 1-x}K{sub x}BiO{sub 3}, with a Tc of 30K, shows a large {sup 18}O isotope effect which indicates that phonons are involved in the pairing mechanism. Superconducting energy gap measurements from IR reflectivity and tunneling are consistent with moderate coupling (2{Delta}/kTc = 3.5 {plus minus} 0.5). A characteristic phonon energy of about 40 meV would be required to obtain the high Tc. Neutron scattering measurements show a large density of phonons in the range 40 to 80 meV and strong coupling of electrons to thse modes is indicated in tunneling spectroscopy. Additional results are reported including the structural phase diagram, which suggest that superconductivity is phonon mediated. (orig.).

  19. Bending damage evolution and its influence on critical current and n-value of Bi2223/Ag superconducting composite tape

    Energy Technology Data Exchange (ETDEWEB)

    Doko, D.; Miyazaki, N. [Graduate Student, Kyoto Univ. (Japan); Ochiai, S.; Okuda, H. [International Innovation Center, Kyoto Univ. (Japan); Oh, S.S. [Korea Electrotechnology Research Inst., Changwon (Korea); Tanaka, M.; Hojo, M.; Osamura, K. [Graduate School of Engineering, Kyoto Univ. (Japan)

    2005-07-01

    Bending behavior of Bi2223/Ag superconducting composite tapes, and the influence of the bending damages on critical superconducting current I{sub c} and n-value that is a measure for the sharpness of the transition from super- to normal conduction, were studied. Following damages, responsible to the reduction in critical current at high bending strains, were observed. (i) Transverse and (ii) longitudinal crackings of the filaments, (iii) interfacial debonding between filaments and silver, and (iv) buckling in compression side. The damage of the filaments arose first locally, resulting in a reduction of the I{sub c} and n-value in the corresponding local portion. The overall I{sub c} and n-values were determined by such a local portion. With increasing strain, the damage of the other portions arose successively, resulting in loss of superconductivity in all portions. (orig.)

  20. 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.

  1. High temperature superconducting with two doping atoms in La-doped Bi-2201 and Y-doped Bi-2212

    OpenAIRE

    Röser, H.P; Huber, F; M. von Schönermark; Nikoghosyan, A

    2009-01-01

    These crystals have two doping patterns given by oxygen excess and doping with an additional atom with projected positions in theCuO2 plane. Both doping elements are necessary for the occurrence of superconductivity. Where the two doping patterns overlap, the point matched locations actas there sonating superconducting pathway and might explain a correlation between Tc and the doping structure.

  2. Development of microstructure and superconductivity of silver-clad Bi(2223) composite tapes in the process of heat treatment

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Y.C. (School of Materials Science and Engineering, Univ. of New South Wales, Kensington (Australia)); Liu, H.K. (School of Materials Science and Engineering, Univ. of New South Wales, Kensington (Australia)); Dou, S.X. (School of Materials Science and Engineering, Univ. of New South Wales, Kensington (Australia))

    1994-02-01

    A systematic study on the development of phase composition, microstructure and superconducting properties (critical temperature Tc and critical current density J[sub c]) in silver-clad (Bi,Pb)[sub 2]Sr[sub 2]Ca[sub 2]Cu[sub 3]O[sub 10] composite tapes during the process of heat treatment has been conducted using X-ray diffraction, scanning electron microscopy and electrical measurements. The correlation between the tape's high Tc phase purity, microstructure and superconducting properties at different heat treatment stages has been carefully analysed and explained. The results indicate that pure high Tc phase, high degree of grain alignment, high mass density and good connection between grains are all essential for superconducting tapes to carry a large current. With the optimized process parameters, a critical current density J[sub c] up to 32665 A cm[sup -2] (corresponding critical current, 42.3 A) at 77 K and self-magnetic field for silver-clad (Bi,Pb)[sub 2]Sr[sub 2]Ca[sub 2]Cu[sub 3]O[sub 10] superconducting composite tapes has been achieved. (orig.)

  3. Superconductivity of Pb, K and Rb-doped BaBiO sub 3. [Ba-Pb-Bc-O; Ba-K-Bi-O; Ba-Rb-Bi-O

    Energy Technology Data Exchange (ETDEWEB)

    Kuentzler, R.; Dossmann, Y. (IPCMS, Groupe d' Etude des Materiaux Metalliques, 67 - Strasbourg (France)); Hornick, C.; Wegner, S.; El Farsi, R.; Drillon, M. (IPCMS, Groupe de Materiaux Inorganiques, EHICS, 67 - Strasbourg (France))

    1991-12-15

    Preparation, structure and superconducting properties of Pb, K and Rb-doped BaBiO{sub 3} are described. The low temperature specific heat results, it is emphasized, concern the complete existing concentration ranges of the systems. No pronounced specific heat peak can be observed at Tc and there is no evidence of a significant linear temperature dependence term. The Debye temperature {theta}{sub D} varies continuously with the concentration of the dopand, which is in favour of a view of superconductivity relating it to high-frequency optic modes. (orig.).

  4. Damage evolution under bending and tensile stress and its influence on critical current of Bi2223/Ag superconducting composite tape

    Energy Technology Data Exchange (ETDEWEB)

    Ochiai, S. E-mail: ochiai@iic.kyoto-u.ac.jp; Miyazaki, N.; Doko, D.; Nagai, T.; Nakamura, M.; Okuda, H.; Oh, S.S.; Hojo, M.; Tanaka, M.; Osamura, K

    2004-08-01

    The influence of bending and tensile damage introduced at room temperature on the critical current at 77 K under zero magnetic field of a multifilamentary Bi2223/Ag/Ag alloy superconducting composite tape was studied. From the analysis of the tensile stress-strain curve, the residual strain and intrinsic tensile-fracture strain of Bi2223 filaments were estimated, with which the measured change of critical current with tensile strain was accounted for. A simple model, in which the damage evolution in both tensile and compressive sides was incorporated, was proposed to describe the change in critical current with bending strain. The application of the model to the experimental result indicated that the intrinsic compressive-strength of Bi2223 filaments, determining damages in the compressive side, is about five times higher than the tensile strength.

  5. Superconductivity

    CERN Document Server

    Poole, Charles P; Farach, Horacio A

    1995-01-01

    Superconductivity covers the nature of the phenomenon of superconductivity. The book discusses the fundamental principles of superconductivity; the essential features of the superconducting state-the phenomena of zero resistance and perfect diamagnetism; and the properties of the various classes of superconductors, including the organics, the buckministerfullerenes, and the precursors to the cuprates. The text also describes superconductivity from the viewpoint of thermodynamics and provides expressions for the free energy; the Ginzburg-Landau and BCS theories; and the structures of the high

  6. 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.

  7. Superconducting properties of multilayered Ag/Bi(Pb)-2223 tapes prepared using pretextured monolayered tapes

    International Nuclear Information System (INIS)

    Multilayered Ag/Bi(Pb)-2223 tapes with high critical current densities (Jc) have been fabricated using partially heat treated, textured monolayered tapes. Cut sections of the monolayered tapes have been stacked one over the other and folded together using high-purity silver foil and further rolled and heat treated to obtain multilayered tapes of different thickness with an HTS layer thickness varying from 9 to 20 μm. A comparison of the superconducting properties of the multilayered tapes with those of monolayered tapes prepared under identical heat treatment conditions shows that the Jc(multi)/Jc(mono) ratio at 77 K is as high as 0.57. The ratio is found to decrease with a decrease in the HTS core thickness of the multilayered tapes. XRD studies of 'banana peeled' samples show that the monolayered tapes at the folding stage acquire a good degree of texturing. The relatively high value of the Jc(multi)/Jc(mono) ratio obtained in the present case compared with those reported by the existing techniques is attributed to the use of pretextured monolayered tapes. (author)

  8. Variation of superconducting and structural parameters of YBa2Cu3O7-δ ceramics under flat deformations

    International Nuclear Information System (INIS)

    Effect of flat deformations on YBa2Cu3O7-δ ceramic behaviour is investigated. It is ascertained that under yttrium ceramics deformation by 1-2 % at T ∼ 300 deg C, a 7-13 K drop of Tc0.5 increase of superconducting transition width from c0.5 drop is explained by occuring plastic deformations and transition width increase-by microdistortions. YBa2Cu3O7-δ behaviour under loading is strongly dependent on the loading temperature and rate

  9. Co-doping induced coexistence of superconductivity and ferromagnetism in Bi3.9Co0.1O4S3

    Science.gov (United States)

    Yu, Chuan; Feng, Zhenjie; Yin, Xunqing; Li, Qing; Kang, Baojuan; Lu, Bo; Jing, Chao; Cao, Shixun; Zhang, Jincang

    2016-09-01

    The effects of Co doping on the physical properties of the Bi4O4S3 system was studied. We discovered that stable Bi3.9Co0.1O4S3 compound exhibits both long-range ferromagnetism and enhanced superconductivity with thermodynamic evidences for Tc ∼ 5.5 K. We found that there is an anomalous feature which represents superconducting transition in the hysteretic M-vs.-H loops for Bi3.9Co0.1O4S3 at T = 3 K.

  10. The effect of MgCO{sub 3} addition on the superconducting properties of Bi2223 superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Abbasi, H., E-mail: Hadi_abbasi1983@yahoo.co [Department of Physics, Superconductivity Research Center, Urmia University, Urmia (Iran, Islamic Republic of); Taghipour, J.; Sedghi, H. [Department of Physics, Superconductivity Research Center, Urmia University, Urmia (Iran, Islamic Republic of)

    2009-08-12

    MgCO{sub 3} particles were introduced into Bi{sub 1.66}Pb{sub .34}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+d}elta powder in various weight fractions. Bulk samples were made from the Bi2223/MgCO{sub 3} powder by the conventional solid state reaction method. The superconducting properties of samples for different amounts of MgCO{sub 3} have been investigated by means of X-ray diffraction, magnetoresistivity. Room temperature X-ray diffraction studies show that there exists two phases, i.e. Bi2223 and Bi2212 in analyzed samples. The volume fraction of Bi2223 phase decreases with increasing MgCO{sub 3} content. It is observed that the lattice parameter c decreases with increasing MgCO{sub 3} content, but a (and/or b) axis does not change considerably. The temperature at which the resistivity becomes zero decreases with increasing dopant content and also with increasing applied magnetic field. The normal state resistivity regularly decreases with the increase in MgCO{sub 3} addition.

  11. 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.

  12. Superconductivity and Shubnikov-de Haas oscillations in the noncentrosymmetric half-Heusler compound YPtBi

    Science.gov (United States)

    Pavlosiuk, Orest; Kaczorowski, Dariusz; Wiśniewski, Piotr

    2016-07-01

    Recent findings of possible topological superconductivity in YPtBi motivated us to grow and investigate single crystals of this material. The compound was studied by means of ac magnetic susceptibility, electrical resistivity, Hall resistivity, and heat capacity measurements, performed in wide ranges of temperature and magnetic field. The superconductivity below the critical temperature Tc=0.97 K was clearly reflected in the magnetic and electronic transport data. The upper critical field Bc 2 was estimated at 1.84 T. However, no obvious anomaly near Tc was found in the temperature dependence of the heat capacity. In the normal state YPtBi appears semimetallic but its electrical conductance can be described by two components corresponding to parallel channels: metallic and semiconducting, with the latter becoming negligible at temperatures below 40 K. Shubnikov-de Haas oscillations were observed at temperatures below 10 K. Nontrivial Berry phase together with weak antilocalization effect strongly support the presence of Dirac fermions in YPtBi.

  13. 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.

  14. 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.

  15. Study of the structure, dielectric and ferroelectric behavior of BaBi4+δTi4O15 ceramics

    Science.gov (United States)

    Khokhar, Anita; Goyal, Parveen K.; Thakur, O. P.; Sreenivas, K.

    2016-05-01

    The structure and ferroelectric properties of excess bismuth doped barium bismuth titanate BaBi4+δTi4O15 (δ = 2 - 10 wt.%)) ceramics prepared by solid-state reaction method have been investigated. X-ray diffraction (XRD) confirms the formation of a single phase material with a change in the orthorhombic distortion with varying excess of bismuth content. There is no change in the phase transition temperature (Tm) while the relaxor behaviour has been modified significantly with excess of bismuth doping. Saturated hysteresis loops with high remnant polarization (Pr ~ 12.5 µC/cm2), low coercive fields (Ec ~ 26 kV/cm) are measured and a high piezoelectric coefficient (d33 ~ 29 pC/N) is achieved in poled BaBi4Ti4O15 ceramics prepared with up to 8 wt.% of excess bismuth oxide. The improvement in the ferroelectric properties with increase in the excess bismuth content in BaBi4Ti4O15 ceramics has been explained in terms of changing oxygen vacancy concentration and structural relaxation. Tunable ferroelectric materials can be obtained by manipulating the doping amount of excess bismuth.

  16. Superconductivity

    International Nuclear Information System (INIS)

    This report contains lecture notes of the basic lectures presented at the 1st Topsoee Summer School on Superconductivity held at Risoe National Laboratory, June 20-24, 1988. The following lecture notes are included: L.M. Falicov: 'Superconductivity: Phenomenology', A. Bohr and O. Ulfbeck: 'Quantal structure of superconductivity. Gauge angle', G. Aeppli: 'Muons, neutrons and superconductivity', N.F. Pedersen: 'The Josephson junction', C. Michel: 'Physicochemistry of high-Tc superconductors', C. Laverick and J.K. Hulm: 'Manufacturing and application of superconducting wires', J. Clarke: 'SQUID concepts and systems'. (orig.) With 10 tabs., 128 figs., 219 refs

  17. 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.

  18. Effect of Heat Treatment Conditions on Properties of Lead-Free Bi2GeO5 Ferroelectric Glass Ceramics

    International Nuclear Information System (INIS)

    Nowadays, lead-free ferroelectric materials have attracted much interest among materials scientists as a result of environmental concern. The bismuth germanate (Bi2GeO5) phase, one of the lead-free ferroelectric crystals, is of particular interest as its composition already contains good glass former (GeO2) and can be prepared by an alternative glass ceramic route. In this work, the conventional melt-quenching method was used to produce the parent glass with composition of 60 mol% BiO1.5:20 mol% GeO2:20 mol% BO1.5. The as-received glass pieces were subjected to the heat treatment schedule at various crystallization temperatures and dwell-times. The glass and glass ceramics samples were then investigated by XRD, Raman spectroscopy and their dielectric properties were also measured. The XRD and Raman spectroscopy showed that the crystallinity of the prepared glass ceramics depended very much on crystallization temperature and dwell-time. The larger dielectric constant and lower dielectric loss were obtained as crystallinity of the glass ceramics enhanced. The highest dielectric constant (εr) was found at 77 with a low dielectric loss of about 0.005.

  19. Synthesis and characterization of ceramics BNO (BiNbO4) added to 10% of CuO

    International Nuclear Information System (INIS)

    The study of the synthesis and structural characterization of ceramic BiNbO4 and behavior of density when added 10% by weight of CuO, with a view to applications in ceramic capacitors, are presented in this work. The BiNbO4 was prepared by conventional ceramic method. The milled powders were calcined for 2 hours at 850 °C for 3 hours and characterized by using a diffractometer Rigaku DMAXB of Co-α radiation. A more detailed characterization by XRD was performed using the program DBWS9807a using the Rietveld refinement of crystal structures, which confirmed the achievement of the α-BNO phase with orthorhombic structure. Were produced buks with the calcined powder, they were sintered at 925 °C. In order to study the grain morphology and distribution of pores in the ceramic body, the surface of the sample by adding 10% of CuO was analyzed by Scanning Electron Microscopy which confirmed a better densification. (author)

  20. 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).

  1. A Study on Nucleation, Crystallization Kinetics, Microstructure and Mechanical Properties of Ru-Bi Partial Substituted BSCCO Glass Ceramics

    Science.gov (United States)

    Tasci, Ahmet Tolga; Ozturk, Ozgur; Gokcen, Tugba; Cavdar, Sukru; Koralay, Haluk; Senol, Abdulkadir

    2015-03-01

    This study deals with, the effects of Ru-Bi partial substitutions on the thermal, structural and mechanical properties of Bi1 . 8 - xRuxPb0.2Sr2CaCu2O10+δ (x =0.0, 0.025, 0.050, 0.075), produced with glass-ceramics method have been investigated. The effects of Ru-Bi Partial substitutions on glass transition, nucleation and crystallization temperature are analyzed by differential thermal analyzer (DTA). Furthermore, micro-structure and micro-mechanical properties of Ru-Bi partial substituted BSCCO glass ceramics have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Vickers microhardness measurements. From the DTA results, nucleation kinetics have been obtained by using Ozawa, Augis-Bennett, Takher and Kissinger equations. Also activation energies and Avrami parameters have been found. Oxidation amount is seen to be increased with increasing Ru concentration in consequence of thermogravimetric analyses results. Moreover, Lattice parameters, volume fractions and surface morphologies of the samples are obtained from XRD and SEM measurements, respectively.

  2. 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}.

  3. 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.

  4. 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.).

  5. Structural properties of superconducting and nonsuperconducting Ba/sub 1-x/K/sub x/BiO/sub 3/

    Energy Technology Data Exchange (ETDEWEB)

    Dabrowsi, B.; Hinks, D.G.; Jorgensen, J.D.; Richards, D.R.; Pei, Shiyou; Zheng, Y.; Mitchell, A.W.

    1989-01-01

    Structural properties of Ba/sub 1-x/K/sub x/BiO/sub 3/ prepared by powder- and melt-process methods are studied. The potassium solubility limit, x = 0.5, is about the same for both methods and probably is determined by the ionic sizes of the constituent ions. Melt- and powder-processed samples of very good quality for superconducting compositions (x > 0.3) can be produced by melting or by repeated grinding, respectively and quenching after N/sub 2/ firing at 725/degree/C. Single phase samples for x < 0.3 can be made without reduction to the trivalent Bi-compound. Preparation of very homogeneous single phase samples for x < 0.3 is difficult due to the low N/sub 2/ synthesis temperatures and the phase separation which occurs above 725/degree/C. 11 refs., 7 figs.

  6. Growth of Bi2Sr2CaCu2O8+δ thin films with enhanced superconducting properties by incorporating CaIrO3 nanoparticles

    Science.gov (United States)

    De Vero, J. C.; Hwang, I.; Santiago, A. C. L.; Chang, J.; Kim, J.; Sarmago, R. V.; Song, J. H.

    2014-04-01

    We synthesized Bi2Sr2CaCu2O8+δ (Bi-2212) thin films with incorporated CaIrO3 (Ca-iridate) nanoparticles, by using pulsed laser deposition and post-growth ex situ annealing. We found that the density of incorporated Ca-iridate strongly affected the superconducting properties and microstructure of the Bi-2212 thin films. Incorporating a low density of Ca-iridate (450 laser pulses) in the Bi-2212 improved its superconducting properties (Tc-onset = 97 K, Tc-zero = 84 K) over those of pure Bi-2212 (Tc-onset = 94 K, Tc-zero = 80 K). However, incorporating a higher density (1800 pulses) significantly reduced Tc-zero to ≈ 57 K. Incorporating a low density of Ca-iridate also decreased the c-axis lattice constant. Films with incorporated Ca-iridate exhibited greater critical current density, Jc(B), than the pure Bi-2212 film. These results indicate that incorporating low densities of Ca-iridate nanoparticles into Bi-2212 can improve its superconducting properties.

  7. 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.

  8. Radio frequency response of Ag-sheathed (Bi, Pb)2Sr2Ca2Cu3O10+x superconducting tapes

    International Nuclear Information System (INIS)

    The response of long (Bi,Pb)2Sr2Ca2Cu3O10 conductors fabricated by the oxide-powder-in-tube method to a radio frequency excitation was investigated while employed as the inductive part of large L-C resonating circuits. After removal of the outer silver sheath, superconducting devices cooled down to 77 K showed superior properties compared to equivalent non-superconducting circuits: Bi-based resonators, conceived for a working frequency in the range between 5 and 17 MHz, presented an improvement of the quality factor by a factor of 20. This result opens new perspectives for the application of Bi-based superconducting materials in the detection of a weak radio frequency signal, as in magnetic resonance imaging. (author)

  9. 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

  10. 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.

  11. CoBi3–the first binary compound of cobalt with bismuth: high-pressure synthesis and superconductivity

    International Nuclear Information System (INIS)

    The first compound in the cobalt bismuth system was synthesized by high-pressure high-temperature synthesis at 5 GPa and 450 °C. CoBi3 crystallizes in space group Pnma (no. 62) with lattice parameters of a = 8.8464(7) Å, b = 4.0697(4) Å and c = 11.5604(9) Å adopting a NiBi3-type crystal structure. CoBi3 undergoes a superconducting transition at Tc = 0.48(3) K as evidenced by electrical-resistivity and specific-heat measurements. Based on the anomaly of the specific heat at Tc and considering the estimated electron-phonon coupling, the new Bi-rich compound can be classified as a Bardeen-Cooper-Schrieffer-type superconductor with weak electron-phonon coupling. Density-functional theory calculations disclose a sizable influence of the spin-orbit coupling to the valence states and proximity to a magnetic instability, which accounts for a significantly enhanced Sommerfeld coefficient. (paper)

  12. Effect of Sm, Co codoping on the dielectric and magnetoelectric properties of BiFeO{sub 3} polycrystalline ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Song, G.L., E-mail: sgl1972@yahoo.cn [College of Physics and Information Engineering, Henan Normal University, 453007 Xinxiang (China); Henan Key laboratory of photovoltaic Materials, 453007 Xinxiang (China); Zhang, H.X. [College of Mathematics and Information Science, Henan Normal University, 453007 Xinxiang (China); Wang, T.X.; Yang, H.G; Chang, F.G. [College of Physics and Information Engineering, Henan Normal University, 453007 Xinxiang (China); Henan Key laboratory of photovoltaic Materials, 453007 Xinxiang (China)

    2012-07-15

    Multiferroic Bi{sub 0.95}Sm{sub 0.05}Fe{sub 1-x}Co{sub x}O{sub 3} (x=0-0.1) ceramics were prepared by the rapid liquid phase sintering method. For all the samples studied, the dielectric constant and dielectric loss decrease with increasing frequency in the range from 1 kHz to 1 MHz. It shows that the dielectric constant of Bi{sub 0.95}Sm{sub 0.05}FeO{sub 3} at 10 kHz is about forty times larger than that of pure BiFeO{sub 3}. This dramatic change in the dielectric properties of Bi{sub 0.95}Sm{sub 0.05}Fe{sub 1-x}Co{sub x}O{sub 3} (x=0-0.1) samples can be understood in terms of the space charge limited conduction associated with crystal defects, which was indicated by the increase of magnetoelectric effect with doping Co{sup 3+} under applied magnetic field from 1 to 8 kOe. It was believed that the ferroelectric polarization enhancement comes from the exchange interaction between the Sm{sup 3+} and Fe{sup 3+} or Co{sup 3+} ions for Bi{sub 0.95}Sm{sub 0.05}Fe{sub 0.95}Co{sub 0.05}O{sub 3} at room temperature. - Highlights: Black-Right-Pointing-Pointer Sm and Co dopants significantly decreased the grain sizes of BFO ceramics from the SEM images. Black-Right-Pointing-Pointer The dielectric constant of Bi{sub 0.95}Sm{sub 0.05}FeO{sub 3} measured at 10 kHz was about forty times larger than that of pure BiFeO{sub 3}. Black-Right-Pointing-Pointer The values of ME effect of Bi{sub 0.95}Sm{sub 0.05}Fe{sub 1-x}Co{sub x}O{sub 3} samples can be enhanced by doping Sm{sup 3+}and Co{sup 3+}. Black-Right-Pointing-Pointer Maximum ME effect as high as 4.2% observed at x=0.05 (Bi{sub 0.95}Sm{sub 0.05}Fe{sub 0.95}Co{sub 0.05}O{sub 3}).

  13. Superconductivity

    International Nuclear Information System (INIS)

    The monograph provides readable introduction to the basics of superconductivity for beginners and experimentalists. For theorists, the monograph provides nice and brief description of the broad spectrum of experimental properties, theoretical concepts with all details, which theorists should learn, and provides a sound basis for students interested in studying superconducting theory at the microscopic level. Special chapter on the theory of high-temperature superconductivity in cuprates is devoted

  14. Growth of Bi sub 2 Sr sub 2 Ca sub 2 Cu sub 3 O sub y superconducting films using the radio-frequency magnetron sputtering method

    CERN Document Server

    Matsumoto, K; Katsurahara, K; Kishida, S; Tokutaka, H

    2002-01-01

    Bi sub 2 Sr sub 2 Ca sub 2 Cu sub 3 O sub y (Bi-2223) superconducting thin films have been prepared by radio-frequency magnetron sputtering using a mixture of helium and oxygen (He:O sub 2 = 4:1) as a sputtering gas. The films were deposited using the single powder targets with the various composition Bi:Sr:Ca:Cu = m:2:2:3 (m = 2-4). The phase of the film changed with use of the various compositions of targets, and a film with a Bi-2223 single phase was obtained using the target of m = 3. Furthermore, the phase and the crystallinity of the films depended on the substrate temperature and the gas pressure. We found the optimum sputtering conditions for the Bi-2223 film with good crystallinity, where the composition of the target, the substrate temperatures and the gas pressures were Bi-3223, 720 deg. C and 100 mTorr, respectively.

  15. 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.

  16. Synthesis, structural and electrical properties of La and Nb modified Bi4Ti3O12 ferroelectric ceramics

    Science.gov (United States)

    Roy, M.; Bala, Indu; Barbar, S. K.; Jangid, S.; Dave, P.

    2011-11-01

    Polycrystalline ceramic samples of Bi4-xLaxTi3O12 (x=0.0, 0.5 and 1) and Bi3.5La0.5Ti3-yNbyO12 (y=0.02 and 0.04) have been synthesized by standard high temperature solid state reaction method using high purity oxides and carbonates. The effect of lanthanum doping on Bi-site and Nb doping on Ti-site on the structural and electrical properties of Bi4Ti3O12 powders was investigated by X-ray diffraction, scanning electron microscopy, dc conductivity and dielectric studies. A better agreement between the observed and calculated X-ray diffraction pattern was obtained by performing the Rietveld refinement with a structural model using the non-centrosymmetric space group Fmmm in all the cases. A better agreement between observed and calculated d-values also shows that the lattice parameters calculated using the Rietveld refinement analysis are better. The increase in lanthanum and niobium contents does not lead to any secondary phases. It is found that La3+ doping reduces the material grain size and changes its morphology from the plate-like form to a spherical staking like form. The substitution of Nb for Ti ions affected the degree of disorder and modified the dielectric properties leading to more resistive ceramic compounds. The shape and size of the grains are strongly influenced by the addition of niobium to the system. The activation energies of all the compounds were calculated by measuring their dc electrical conductivities. The frequency and temperature dependent dielectric behavior of all the compounds have also been studied and the results are discussed in detail. The substitution of La and Nb on the Bi and Ti sites decreased the Tc and improved the dielectric and ferroelectric behavior.

  17. 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.

  18. Nanomechanical behavior of 3D porous metal–ceramic nanocomposite Bi/Bi{sub 2}O{sub 3} films

    Energy Technology Data Exchange (ETDEWEB)

    Domingo-Roca, R. [Departament de Física , Universitat Autònoma de Barcelona , E-08193 Bellaterra (Spain); Esqué-de los Ojos, D., E-mail: Daniel.Esque@uab.cat [Departament de Física , Universitat Autònoma de Barcelona , E-08193 Bellaterra (Spain); Guerrero, M., E-mail: Miguel.Guerrero@uab.cat [Departament de Física , Universitat Autònoma de Barcelona , E-08193 Bellaterra (Spain); Pellicer, E.; Baró, M.D.; Suriñach, S. [Departament de Física , Universitat Autònoma de Barcelona , E-08193 Bellaterra (Spain); Sort, J. [Institució Catalana de Recerca i Estudis Avançats (ICREA) and Departament de Física , Universitat Autònoma de Barcelona, E-08193 Bellaterra (Spain)

    2015-02-25

    The nanomechanical properties of three-dimensional (3D) porous metal/metal oxide composite (Bi/Bi{sub 2}O{sub 3}) films grown by direct current electrodeposition have been studied by nanoindentation at two different loading rates. The synthesized films exhibit a mixture of crystallographic phases of metallic Bi and α-Bi{sub 2}O{sub 3}, as evidenced by X-ray diffraction. An in-situ compaction of the sample during the nanoindentation assays has been observed. This in-situ compaction has an influence over both the hardness and elastic modulus of the material, being more important on the latter and, therefore, on the determination of the degree of porosity of the composite film. The influence of the loading rate on the mechanical properties has been investigated. In addition, time-dependent deformation processes (creep tests) have been also performed, revealing an anelastic behavior irrespective of the loading rate. From these creep tests, a viscoelastic non-Newtonian behavior of the sample is evidenced, which is well-described by a three-element Voigt model.

  19. Superconductivity

    CERN Document Server

    Ketterson, John B

    2008-01-01

    Conceived as the definitive reference in a classic and important field of modern physics, this extensive and comprehensive handbook systematically reviews the basic physics, theory and recent advances in the field of superconductivity. Leading researchers, including Nobel laureates, describe the state-of-the-art in conventional and unconventional superconductors at a particularly opportune time, as new experimental techniques and field-theoretical methods have emerged. In addition to full-coverage of novel materials and underlying mechanisms, the handbook reflects continued intense research into electron-phone based superconductivity. Considerable attention is devoted to high-Tc superconductivity, novel superconductivity, including triplet pairing in the ruthenates, novel superconductors, such as heavy-Fermion metals and organic materials, and also granular superconductors. What’s more, several contributions address superconductors with impurities and nanostructured superconductors. Important new results on...

  20. Study of high field Nb3Sn superconducting dipoles: electrical insulation based made of ceramic and magnetic design

    International Nuclear Information System (INIS)

    In the framework of LHC upgrades, significant efforts are provided to design accelerator magnets using the superconducting alloy Nb3Sn, which allows to reach higher magnetic fields (≥12 T). The aim of this thesis is to propose new computation and manufacturing methods for high field Nb3Sn dipoles. A ceramic insulation, previously designed at CEA Saclay, has been tested for the first time on cables, in an accelerator magnet environment. Critical current measures, under magnetic field and mechanical stress, have been carried out in particular. With this test campaign, the current ceramic insulation has been shown to be too weak mechanically and the critical current properties are degraded. Then a study has been conducted, with the objective to improve the mechanical strength of the insulation and better distribute the stress inside the cable. Methods of magnetic design have also been proposed, in order to optimize the coils shape, while fulfilling constraints of field homogeneity, operational margins, forces minimization... Consequently, several optimization codes have been set up. They are based on new methods using analytical formulas. A 2D code has first been written for block designs. Then two 3D codes have been realized for the optimization of dipole ends. The former consists in modeling the coil with elementary blocs and the latter is based on a modeling of the superconducting cables with ribbons. These optimization codes allowed to propose magnetic designs for high field accelerator magnets. (author)

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

    International Nuclear Information System (INIS)

    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−1 K−1 and those for the Bi2223/Ag-CA tape were 206 and 206 W m−1 K−1, respectively, the values of which were approximately 30–40% and 10–15% smaller than those of the standard Bi2223/Ag tape

  2. Investigate on the application of elliptical drawing dies during the manufacturing process of Bi-2223/Ag superconducting tapes

    Energy Technology Data Exchange (ETDEWEB)

    Liu, R. [Tsinghua University, Beijing 100084 (China); Innova Superconductor Technology Co., Ltd., 7 Rongchang Dongjie, Longsheng Industrial Park, Beijing Economic and Technological Development Area, Beijing 100176 (China)], E-mail: liuruiliyu@sina.com; Qu, T.-M. [Tsinghua University, Beijing 100084 (China); Zhang, J.-S.; Song, X.-H. [Innova Superconductor Technology Co., Ltd., 7 Rongchang Dongjie, Longsheng Industrial Park, Beijing Economic and Technological Development Area, Beijing 100176 (China); Liang, T. [Tsinghua University, Beijing 100084 (China); Liu, Q. [Chongqing University, Chongqing 400044 (China); Han, Z. [Tsinghua University, Beijing 100084 (China); Innova Superconductor Technology Co., Ltd., 7 Rongchang Dongjie, Longsheng Industrial Park, Beijing Economic and Technological Development Area, Beijing 100176 (China)

    2008-09-15

    Elliptical drawing (ED) dies were used during the manufacturing process of Bi-2223/Ag superconducting tapes and their influence on the tapes' homogeneity and critical currents (I{sub c}) has been investigated. By comparing two types of HTS tapes drawn by ED dies and a set of reference round dies, we found that the ED process can improve the qualities of the rolled tapes, such as improving the homogeneity of both the center and the peripheral filaments of the tapes, reducing the micro-cracks caused by the rolling process. Thus, the ED process can increase the I{sub c} and engineering critical current density (J{sub e}) values of HTS tapes.

  3. Stripe-like nanoscale structural phase separation in superconducting BaPb1-xBixO3

    Energy Technology Data Exchange (ETDEWEB)

    Giraldo-Gallo, P.; Zhang, Y.; Parra, C.; Manoharan, H. C.; Beasley, M. R.; Geballe, T. H.; Kramer, M. J.; Fisher, I. R.

    2015-09-16

    The phase diagram of BaPb1-xBixO3 exhibits a superconducting dome in the proximity of a charge density wave phase. For the superconducting compositions, the material coexists as two structural polymorphs. Here we show, via high-resolution transmission electron microscopy, that the structural dimorphism is accommodated in the form of partially disordered nanoscale stripes. Identification of the morphology of the nanoscale structural phase separation enables determination of the associated length scales, which we compare with the Ginzburg–Landau coherence length. We find that the maximum Tc occurs when the superconducting coherence length matches the width of the partially disordered stripes, implying a connection between the structural phase separation and the shape of the superconducting dome.

  4. 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.

  5. 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)

  6. 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.

  7. 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.

  8. 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.

  9. Superconductivity in Ba sub 1 sub - sub x K sub x BiO sub 3 : possible scenario of spatially separated Fermi-Bose mixture

    CERN Document Server

    Menushenkov, A P; Kuznetsov, A V; Kagan, M Y

    2001-01-01

    A new scenario for the metal-insulator phase transition and superconductivity in the perovskite-like bismuthates Ba sub 1 sub - sub x K sub x BiO sub 3 (BKBO) is proposed. It is shown that two types of charge carriers, the local pairs (real-space bosons) and the itinerant electrons, exist in the metallic compound BKBO (x >= 0.37). The real-space bosons are responsible for the charge transport in semiconducting BaBiO sub 3 and for superconductivity in the metallic BKBO. The appearance of the Fermi-liquid state as the percolation threshold is overcome (x >= 0.37) explains the observed metal-insulator phase transition. Because bosons and fermions occupy different types of the octahedral BiO sub 6 complexes, they are separated in real space, and therefore, the spatially separated Fermi-Bose mixture of a new type is likely to be realized in the bismuthates. The nature of superconductivity is consistently explained in the framework of this scenario. A new superconducting oxide Ba sub 1 sub - sub x La sub x PbO sub ...

  10. 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.

  11. Corrosion behavior of Al-Fe-sputtering-coated steel, high chromium steels, refractory metals and ceramics in high temperature Pb-Bi

    International Nuclear Information System (INIS)

    Corrosion tests of Al-Fe-coated steel, high chromium steels, refractory metals and ceramics were carried out in high temperature Pb-Bi at 700 C degrees. Oxygen concentrations in this experiment were 6.8*10-7 wt.% for Al-Fe-coated steels and 5*10-6 wt.% for high chromium steels, refractory metals and ceramics. All specimens were immersed in molten Pb-Bi in a corrosion test pot for 1.000 hours. Coating was done with using the unbalanced magnetron sputtering (UBMS) technique to protect the steel from corrosion. Sputtering targets were Al and SUS-304. Al-Fe alloy was coated on STBA26 samples. The Al-Fe alloy-coated layer could be a good protection layer on the surface of steel. The whole of the Al-Fe-coated layer still remained on the base surface of specimen. No penetration of Pb-Bi into this layer and the matrix of the specimen. For high chromium steels i.e. SUS430 and Recloy10, the oxide layer formed in the early time could not prevent the penetration of Pb-Bi into the base of the steels. Refractory metals of tungsten (W) and molybdenum (Mo) had high corrosion resistance with no penetration of Pb-Bi into their matrix. Penetration of Pb-Bi into the matrix of niobium (Nb) was observed. Ceramic materials were SiC and Ti3SiC2. The ceramic materials of SiC and Ti3SiC2 had high corrosion resistance with no penetration of Pb-Bi into their matrix. (authors)

  12. Magnetoresistance and noise of electric transportation in ceramics samples of (Bi-Pb)2 Sr2 Ca2 Cu3 O10+delta

    International Nuclear Information System (INIS)

    In the work is a study of the influence of the structure on the magnetoresistance and the noise of electric transport (measured via transportation) granular polycrystalline superconducting (Bi-Pb)2 Sr2 Ca2 Cu3 O10+delta. The samples were obtained for different pressures of uniaxial compaction in the range of 100 to 250 MPa. A comparative analysis of the diffraction patterns of X-rays carried out a sample in the form of powder and ceramic samples obtained at different compaction pressures shows that all have a similar chemical composition. The values of the parameters a, b and c of the unit cell are similar in all cases. In addition, found that the increase in uniaxial compaction pressure improves alignment of grains, preferably with axis parallel to the direction of compaction c. To show the influence of variations in structure granular on the transport properties of the material were carried out measurements of magnetoresistance, R (Ba). These curves adjustment was carried out within the framework of the flow trapped immunoregulating model, this polycrystalline material was considered as an arrangement series - parallel of Josephson devices. The results reveal differences in dependency (R) (Ba) measured in samples obtained at different compaction pressures. These differences are reproduced in the model by varying the parameters of the distribution of beads border angles. At the same time, changes in dependence on R (Ba) are reflected in the noise of transport, which is defined as the sudden redeployment of local electrical currents in arrangement with the increase of the applied magnetic field. Analysis of the noise of transport proves to be a technique suitable for the study of the microstructural for being sensitive to minor changes changes.

  13. Submicron-scale high- Tc superconducting Bi-2212 stack fabrication for single-Cooper-pair tunneling

    Science.gov (United States)

    Kim, S.-J.; Latyshev, Yu. I.; Yamashita, T.; Sato, N.; Kishida, S.

    2000-07-01

    We report the characteristics of Bi-2212 intrinsic Josephson junctions (IJJ) showing single-Cooper-pair tunneling effect with a decrease of their in-plane area, S, smaller than a micron scale. The junctions show the typical slope of critical current and current peak-like structure up to 37 K.

  14. 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.

  15. 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.

  16. 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.

  17. Electrical studies on Zr-modified Bi3.25La0.75Ti3O12: a promising FRAM ceramic

    Science.gov (United States)

    Thirumal Reddy, N.; Prasad, N. V.; Kumar, G. S.; Prasad, G.

    2014-12-01

    Zr-modified Auruvillius family of lanthanum bismuth titanate, namely Bi3.25La0.75Ti3-xZrxO12 (BLTZ, x = 0, 0.1, 0.3, 0.5, 0.7 and 1), was prepared by solid-state reaction method. Dielectric properties of the ceramics were studied as a function of temperature. Hysteresis measurements were also performed. Among the composition, Bi3.25La0.75Ti2.9Zr0.1O12 (BLTZ1) showed large remnant polarization compared to the promising ceramic, namely Bi3.25La0.75Ti3O12. The results were corroborated with the pyroelectric, electric polarization and Raman spectroscopic data.

  18. 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.

  19. New dielectric ceramics Pb(Cd)BiM/sup IV/SbO/sub 7/ (M/sup IV/ = Ti, Zr, Sn) with the pyrochlore structure

    International Nuclear Information System (INIS)

    Dielectric ceramics have been obtained by natural sintering of pyrochlore phases with general formula Pb(Cd)BiM/sup IV/SbO/sub 7/ (M/sup IV/ = Ti, Zr, Sn). Low frequency dielectric characteristics have been studied with respect to the processing conditions: sintering without additive and in the presence of some low melting compounds (PbO, Pb/sub 5/Ge/sub 3/O/sub 11/, Bi/sub 12/PbO/sub 19/ and Bi/sub 12/CdO/sub 19/). The dielectric constants of these ceramics lie between 30 and 60, the dielectric losses range from 10 to 30.10/sup -4/ and the temperature coefficient of the dielectric constants (20 - 1000C) can be tailored by means of additives in the +- 30 ppm K/sup -1/ range

  20. Evaluating the chemical compatibility of potential substrate materials for Bi-Sr-Ca-Cu-O films

    International Nuclear Information System (INIS)

    Potential substrate and buffer layer materials for Bi2Sr2CaCu2Ox (BSCCO) were surveyed using bulk ceramic processing techniques. Of the materials tested, only Ag was inert with respect to BSCCO. MgO slightly degrades the superconducting onset temperature and volume fraction. LaGaO3 may be a feasible ceramic substrate for BSCCO, although some reaction appears to occur

  1. Superconductivity

    International Nuclear Information System (INIS)

    During 2007, a large amount of the work was centred on the ITER project and related tasks. The activities based on low-temperature superconducting (LTS) materials included the manufacture and qualification of ITER full-size conductors under relevant operating conditions, the design of conductors and magnets for the JT-60SA tokamak and the manufacture of the conductors for the European dipole facility. A preliminary study was also performed to develop a new test facility at ENEA in order to test long-length ITER or DEMO full-size conductors. Several studies on different superconducting materials were also started to create a more complete database of superconductor properties, and also for use in magnet design. In this context, an extensive measurement campaign on transport and magnetic properties was carried out on commercially available NbTi strands. Work was started on characterising MgB2 wire and bulk samples to optimise their performance. In addition, an intense experimental study was started to clarify the effect of mechanical loads on the transport properties of multi-filamentary Nb3Sn strands with twisted or untwisted superconducting filaments. The experimental activity on high-temperature superconducting (HTS) materials was mainly focussed on the development and characterisation of YBa2Cu3O7-X (YBCO) based coated conductors. Several characteristics regarding YBCO deposition, current transport performance and tape manufacture were investigated. In the framework of chemical approaches for YBCO film growth, a new method, developed in collaboration with the Technical University of Cluj-Napoca (TUCN), Romania, was studied to obtain YBCO film via chemical solution deposition, which modifies the well-assessed metallic organic deposition trifluoroacetate (MOD-TFA) approach. The results are promising in terms of critical current and film thickness values. YBCO properties in films with artificially added pinning sites were characterised in collaboration with TUCN and

  2. Study on the formation of the liquid phase during heating process of Bi-2223/Ag superconducting tapes at various oxygen partial pressure by using in situ resistance measurement

    International Nuclear Information System (INIS)

    The resistance of T-phase tape and O-phase tape was in situ measured during heating at various oxygen partial pressures. The resistance increased at a characteristic temperature, which was related to the formation of the liquid phase. The formation temperature of the liquid phase increased with increasing oxygen partial pressure. And the formation temperature of the liquid phase of T-phase tape was about 6 deg. C higher than that of O-phase tape. Two kinds of green mono-filament Bi-2223/Ag superconducting tapes (T-phase tape and O-phase tape) were investigated, the initial superconducting phase of which was tetragonal Bi-2212 phase and orthorhombic (Bi,Pb)-2212 phase, respectively. The resistance of these tapes was in situ measured during heating at various oxygen partial pressures. It was found that the resistance increased at a characteristic temperature at every oxygen partial pressure. This resistance behavior was related to the formation of the liquid phase. The formation temperature of the liquid phase increased with increasing oxygen partial pressure. And the formation temperature of the liquid phase of T-phase tape was about 6 deg. C higher than that of O-phase tape. The above results demonstrated that the in situ resistance measurement is a sensitive method for studying the formation of the liquid phase in superconducting materials.

  3. Thermal Evolution of Dielectric and Piezoelectric properties of Lead-Free Submicron-Structured (Bi0.5Na0.5)0.94Ba0.06TiO3 Ceramics

    OpenAIRE

    Pardo, Lorena; Mercadelli, Elisa; Garc?a, Alvaro; Breb?l, Klaus; Galassi, Carmen

    2010-01-01

    The challenge to develop high piezoelectric sensitivity and lead-free compositions ferroelectric ceramics has bring new interest to the study of some classical ferroelectrics as (Bi0.5Na0.5)TiO3 and its solid solutions. The composition near the MPB of the system (1-x) (Bi0.5Na0.5)TiO3-xBaTiO3 with x=0.06 (BNBT6) was found to have interesting properties as lead-free piezoelectric ceramic. Processing of ceramics from nanopowders allows getting fine grained, submicron structured, ceramics that a...

  4. Evidence for phonon-mediated coupling in superconducting Ba/sub 0. 6/K/sub 0. 4/BiO/sub 3/

    Energy Technology Data Exchange (ETDEWEB)

    Hinks, D.G.; Dabrowski, B.; Richards, D.R.; Jorgensen, J.D.; Pei, Shiyou; Zasadzinski, J.F.

    1989-01-01

    Superconducting Ba/sub 0.6/K/sub 0.4/BiO/sub 3/, with a T/sub c/ of 30K, shows a large /sup 18/O isotope effect which indicates that phonons are involved in the pairing mechanism. Infrared reflectivity measurements indicate a value for the superconducting gap consistent with moderate coupling (2..delta../kT/sub c/ = 3.5 +- 0.5). A mediating energy for pairing of about 40 MeV would be required to obtain a T/sub c/ of 30K. Strong coupling of electrons by optical phonons (which are present in this material with energies up to 80 MeV) could account for the observed transition temperature. Recent tunneling spectroscopy shows the presence of strongly coupled optical phonons in the 40 to 70 MeV region, indicating that superconductivity in this material may be phonon mediated. 8 refs., 11 figs.

  5. 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.

  6. 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.

  7. Glass ceramics for high - Tc superconductors

    International Nuclear Information System (INIS)

    Glass formation in the BiO1.5-Ca0.5-Sr0.5O-CuO quasiternary oxide system was examined by the twin-roller and metal-plate quenching techniques. The crystallization process and kinetics were systematically studied by differential thermal and thermogravimetric analysis, X-ray diffraction, and electron microscopy as well as electrical measurements. The route and kinetic properties of crystallization were shown to have a strong compositional dependence. It was found that the growth of crystals in the glasses can be accelerated in the presence of an electrical field. A temperature gradient-related orientation of crystallization was revealed in the Bi-based glasses. This has been ascribed to the large crystallographic anisotropy of the superconducting crystals. The effects of compositions, annealing conditions, and oxygen deficiency on the superconductivity in the Bi-Ca-Sr-Cu-0 glass ceramics are also discussed. 27 refs., 2 tabs., 13 figs

  8. 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+.

  9. 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+.

  10. 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.

  11. Effect of Ag additions on shock wave degradation of superconductivity in Bi-Pb-Sr-Ca-Cu-O and Y-Ba-Cu-O

    International Nuclear Information System (INIS)

    While it has been successfully demonstrated that Bi-Pb-Sr-Ca-Cu-O and YBa2Cu3Ox powders as well as mixtures of these powders along with silver and copper can be shock fabricated in metal or alloy matrices, it has been found that their superconducting properties are degraded by the shock wave. In shock fabricating Bi7Pb3Sr10Ca10Cu15Ox, it has been observed that at peak shock pressures of 4 GPa and above, the as-shocked material behaves as a semiconductor and there is no transition or superconducting onset in the resistance-temperature (R-T) signature. A transition was recently seen for the first time in Bi7Pb3Sr10Ca10Cu15Ox with plane wave shock loading at 1.5 GPa peak shock pressure. However, even at such a low peak pressure, the R-T signature showed signs of residual degradation: the normal state resistivity was semiconducting and it showed a two phase transition with a Tc(R=O) of about 77 K. The R-T signatures of these degraded samples could, however, be completely recovered on proper heat treatment (typically around 860 degrees C in flowing air for 90 hours). The results of the effect of the shock wave on Bi7Pb3Sr10Ca10Ci15Ox and YBa2Cu3Ox at different Ag doping levels is presented in this paper

  12. The generation of 25.05 T using a 5.11 T Bi2Sr2CaCu2Ox superconducting insert magnet

    International Nuclear Information System (INIS)

    A 25.05 T magnetic field was generated by a 5.11 T superconducting Bi2Sr2CaCu2Ox insert magnet within a 19.94 T resistive magnet. The Bi2Sr2CaCu2Ox magnet is constructed using fully reacted powder-in-tube conductor and insulated stainless steel reinforcement. Three concentric sections are used to minimize the total stress in the Bi2Sr2CaCu2Ox conductor: two double pancake stacks and an outer layer-wound section. The insert coil operates at 4.2 K in a 0.168 m diameter cryostat fitted to the resistive magnet. Here we provide an overview of the design and construction of the insert and the results of self-field and in-field testing. Mechanical and electrical safety issues, related to testing in a large resistive magnet, are discussed

  13. 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.

  14. 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.

  15. 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.

  16. Drawing of single filament wire for production of superconducting BiSrCaCuO/Ag composites

    Energy Technology Data Exchange (ETDEWEB)

    Malberg, M.; Bay, N. [Technical Univ. of Denmark, Dept. of Manufacturing Engineering, Lyngby (Denmark); Skov-Hansen, P. [Nordic Superconductor Technologies, Broendby (Denmark)

    1998-12-31

    Superconducting wire is often produced by the powder-in-tube method involving a number of different mechanical processes, among these multi-step drawing operations of single filament wire. A silver tube is filled with powder (BiSrCaCuO). This composite is drawn in up to 100 steps, from an initial diameter of 20 mm to the final one of 1 mm. The present paper shows how one of the main parameters, the reduction, influences the mechanical properties of the single filament wire during drawing. The biggest acceptable reduction per drawing step is determined. In powder compaction tests a linear relationship between micro-hardness and powder density is determined. This relationship is applied for determination of the density distribution in the cross section of drawn single filament wire. It is found that the drawing process causes an increase of the powder compaction near the interface between the silver and powder, whereas the density increase near the center axis of the tube is small. The average density determined in this way corresponds well with the one determined by geometrical measurements. (au)

  17. 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.

  18. Enhanced magnetization with unusual low temperature magnetic ordering behaviour and spin reorientation in holmium-modified multiferroic BiFeO3 perovskite ceramics

    International Nuclear Information System (INIS)

    Holmium-doped Bi1−xHoxFeO3 (x = 0, 0.025, 0.05, 0.075 and 0.10) perovskite ceramics were synthesized by a rapid liquid phase quenching process. The structural analysis performed using x-ray diffraction suggested phase formation with distorted rhombohedral structure in all the synthesized ceramic samples. Rietveld analysis of x-ray diffraction patterns and Raman spectroscopy also confirmed the distorted perovskite structure with R3c symmetry. Optical studies showed characteristic bending vibrations of O − Fe − O, Fe − O stretching and visible range PL emissions in modified BiFeO3 ceramics. Ferromagnetic characteristics were shown by all the holmium-doped samples at room temperature and 5 K. Very high saturation magnetization (at 7 T), four to six times higher at 5 K than at 300 K, is observed for holmium-doped ceramic samples. A complex temperature dependence of magnetization behaviour is observed for holmium-doped samples, which is indicative of a spin reorientation in doped ceramics. (paper)

  19. Enhanced magnetization with unusual low temperature magnetic ordering behaviour and spin reorientation in holmium-modified multiferroic BiFeO3 perovskite ceramics

    Science.gov (United States)

    Singh, Hemant; Yadav, K. L.

    2015-05-01

    Holmium-doped Bi1-xHoxFeO3 (x = 0, 0.025, 0.05, 0.075 and 0.10) perovskite ceramics were synthesized by a rapid liquid phase quenching process. The structural analysis performed using x-ray diffraction suggested phase formation with distorted rhombohedral structure in all the synthesized ceramic samples. Rietveld analysis of x-ray diffraction patterns and Raman spectroscopy also confirmed the distorted perovskite structure with R3c symmetry. Optical studies showed characteristic bending vibrations of O - Fe - O, Fe - O stretching and visible range PL emissions in modified BiFeO3 ceramics. Ferromagnetic characteristics were shown by all the holmium-doped samples at room temperature and 5 K. Very high saturation magnetization (at 7 T), four to six times higher at 5 K than at 300 K, is observed for holmium-doped ceramic samples. A complex temperature dependence of magnetization behaviour is observed for holmium-doped samples, which is indicative of a spin reorientation in doped ceramics.

  20. Pinning and vortex dynamics in superconducting (K, Ba)BiO3 single crystals

    International Nuclear Information System (INIS)

    Pinning and vortex dynamics have been investigated in the 3-dimensional copper free (K,Ba)BiO3 superconductor (Tc ∼ 31K) by magnetization and transport measurements up to 30 Tesla. The magnetization curves present a pronounced fishtail effect which persists for time scales down to 10-4s (pulsed field measurements). The authors show that it is an intrinsic feature of the critical current which can in part be well described by the collective pinning theory. Furthermore, this system presents evidence for a vortex liquid/glass transition for vanishingly small currents. As the current density is increased, dissipation in the glass state is dominated by creep effects. The temperature and current dependence of the activation energy is discussed

  1. Correlation of coupling losses and time constants in superconducting Bi-2223 tapes

    International Nuclear Information System (INIS)

    Ac-loss and coupling current time constant measurements were performed with a large variety of Bi-2223 tape conductors at 4.2 and at 77 K. Single tapes in a perpendicular field as well as stacks of tapes in perpendicular and parallel fields were investigated. The frequency dependence of the coupling loss curve has a maximum which is set in correlation to the separately measured time constant. The theoretical treatment of the time constant and loss measurements using a slab model shows a very good agreement between the position of loss maxima and measured time constants. Eddy currents in the silver matrix, which are described by a second smaller time constant, contribute substantially to the losses in the higher frequency range and may lead to the appearance of a second maximum in the loss curve

  2. 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.

  3. 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.

  4. Synthesis and characterization of BNO (BiNbO4) ceramics added to 3% of ZnO; Sintese e caraterizacao da ceramica BNO (BiNbO4) adicionada com 3% de ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Sales, A.J.M.; Pires Junior, G.F.M.; Rodrigues, H.O.; Sousa, D.G., E-mail: jeffsales.brasil@gmail.com [Universidade Federal do Ceara (DETI/UFC), Fortaleza, CE (Brazil). Dept. de Teleinformatica; Sales, J.C. [Universidade Estadual Vale do Acarau (UVA), Sobral, CE (Brazil). Dept. de Engenharia Civil; Sombra, A.S.B. [Universidade Federal do Ceara (LOCEM/UFC), Fortaleza, CE (Brazil). Dept. de Fisica. Lab. de Telecomunicacoes e Ciencias e Engenharia de Materiais

    2012-07-01

    This work describes the synthesis and study of the structural characterization of ceramic BiNbO4 and density behavior when added 3% by weight of ZnO with a view to use in capacitors. The manufacture of BiNbO4 was made by conventional ceramic method. The powders were milled for two hours, calcined at 850 ° C for 3 h and characterized by XRD with Diffractometer Rigaku DMAXB of Co-α radiation. A more detailed XRD characterization was performed with the program DBWS9807a using the Rietveld refinement of crystal structures, which confirmed the achievement of phase -α-BiNbO4. Were made 'buks' with the calcined powder and these were sintered at 1025 ° C. In order to study the grain morphology and distribution of pores in the ceramic body, the surface of the sample with addition of 3% by weight of ZnO was analyzed by Scanning Electron Microscopy which confirmed a better densification. (author)

  5. 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.

  6. NTCR Behavior of La-Doped BaBiO3 Ceramics

    Directory of Open Access Journals (Sweden)

    Ying Luo

    2009-01-01

    Full Text Available The influence of the composition on the microstructure and electrical properties of BaBi1-xLaxO3  (0≤x≤0.1 NTC thermistors was investigated. A single phase of BaBi1−xLaxO3 with a monoclinic structure was prepared by solid state reaction method. The relationship between the resistivity and the reciprocal of absolute temperature of the prepared NTC thermistors was linear, indicative of NTC characteristics. The resistivity and the coefficient of temperature sensitivity first decreased with increasing x in the range of x<0.03 and then increased with further increase in x. However the alpha parameter value increased to a maximum value and then decreased again.

  7. 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.

  8. Synthesis and characterization of ceramics BNO (BiNbO4) added to 10% of CuO; Sintese e caracterizacao da ceramica BNO (BiNBO{sub 4}) adicionada com 10% de CuO

    Energy Technology Data Exchange (ETDEWEB)

    Sales, A.J.M.; Silva, P.M.O.; Rodrigues Junior, C.A., E-mail: jeffsales.brasil@gmail.com [Universidade Federal do Ceara (DETI/UFC), Fortaleza, CE (Brazil). Dept. de Teleinformatica; Sales, J.C.; Silva, M.A.S. da [Universidade Estadual Vale do Acarau (UVA), Sobral, CE (Brazil); Sombra, A.S.B. [Universidade Federal do Ceara (LOCEM/UFC), Fortaleza, CE (Brazil). Dept. de Fisica. Lab. de Telecomunicacoes e Ciencias e Engenharia de Materiais

    2012-07-01

    The study of the synthesis and structural characterization of ceramic BiNbO4 and behavior of density when added 10% by weight of CuO, with a view to applications in ceramic capacitors, are presented in this work. The BiNbO4 was prepared by conventional ceramic method. The milled powders were calcined for 2 hours at 850 °C for 3 hours and characterized by using a diffractometer Rigaku DMAXB of Co-α radiation. A more detailed characterization by XRD was performed using the program DBWS9807a using the Rietveld refinement of crystal structures, which confirmed the achievement of the α-BNO phase with orthorhombic structure. Were produced buks with the calcined powder, they were sintered at 925 °C. In order to study the grain morphology and distribution of pores in the ceramic body, the surface of the sample by adding 10% of CuO was analyzed by Scanning Electron Microscopy which confirmed a better densification. (author)

  9. Transport Barkhausen-like noise in uniaxially pressed Bi1.65Pb0.35Sr2Ca2Cu3O10+δ ceramic samples

    International Nuclear Information System (INIS)

    We report on the detection of the transport Barkhausen-like noise (TBN) in polycrystalline samples of Bi1.65Pb0.35Sr2Ca2 Cu3O10+δ (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 ∼ 1 Hz) with maximum amplitude Bmax ∼ 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, Ba(ti), 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-Tc superconductors.

  10. 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.

  11. Structural and electromechanical properties of Na0.5Bi0.5TiO3 ceramics produced by different synthesis routes

    Science.gov (United States)

    Hussain, A.; Maqbool, A.; Malik, R. A.; Kim, M. H.; Song, T. K.; Kim, W. J.

    2016-08-01

    Sodium bismuth titanate, Na0.5Bi0.5TiO3 (NBT) ceramics were produced by three different methods; conventional mixed-oxide (CMO) route, molten salt synthesis (MSS) and topochemical microcrystal conversion (TMC) and then sintered at 1150 oC for 2 h in air atmosphere. The crystal structure, dielectric, ferroelectric and field-induced strain properties were investigated for all samples. All samples showed a single phase perovskite structure without any evidences of unwanted secondary phases. The NBT ceramics synthesized by the TMC method show slightly better dielectric, ferroelectric and field induced strain response as compared with CMO and MSS synthesized ceramics. The room temperature dielectric constant measured at 1 kHz increased from 218 for NBT ceramics synthesized by MSS method to 271 and 330 for CMO and TMC synthesized ceramics, respectively. Similarly, the dynamic piezoelectric coefficient (d 33*) enhanced from 91 pm/V for CMO synthesized to 97 pm/V and 107 pm/V for MSS and TMC synthesized ceramics, respectively.

  12. 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.

  13. Influence of processing route on electrical properties of Bi{sub 4}Ti{sub 3}O{sub 12} ceramics obtained by tape-casting technology

    Energy Technology Data Exchange (ETDEWEB)

    Ranieri, M.G.A., E-mail: gabi.ranieri@ig.com.br [São Paulo State University, UNESP – Engineering Faculty, Guaratinguetá, SP 12516-410 (Brazil); Aguiar, E.C.; Cilense, M. [São Paulo State University, UNESP – Chemistry Institute, Araraquara, SP 14800-900 (Brazil); Stojanovic, B.D. [Institute for Multidisciplinary Research, University of Belgrade, Kneza Viseslava 1, Belgrade (Serbia); Simões, A.Z., E-mail: alezipo@yahoo.com [São Paulo State University, UNESP – Engineering Faculty, Guaratinguetá, SP 12516-410 (Brazil); Varela, J.A. [São Paulo State University, UNESP – Chemistry Institute, Araraquara, SP 14800-900 (Brazil)

    2015-10-15

    Highlights: • Bi{sub 4}Ti{sub 3}O{sub 12} thick films were obtained by SSR and PPM methods. • Both systems crystallize in an orthorhombic structure. • Textured characteristics were evidenced. • Grain morphology affects the P–E loops. - Abstract: Bismuth titanate powders (Bi{sub 4}Ti{sub 3}O{sub 12}-BIT) were fabricated by solid state reaction (SSR) and polymeric precursor method (PPM). From these powders, Bi{sub 4}Ti{sub 3}O{sub 12} pellets were obtained by tape-casting using plate-like templates particles prepared by a molten salt method. The BIT phase crystallizes in an orthorhombic structure type with space group Fmmm. Agglomeration of the particles, which affects the densification of the ceramic, electrical conduction and leakage current at high electric fields, was monitored by transmission electronic microscopy (TEM) analyses. FEG-SEM indicated that different shape of grains of BIT ceramics was influenced by the processing route. Both SSR and PPM methods lead to unsaturated P–E loops of BIT ceramics originating from the highly c-axis orientation and high conductivity which was affected by charge carriers flowing normally to the grain boundary of the crystal lattice.

  14. 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.

  15. 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.

  16. Possibilities of producing texturised ceramics and increasing the density of critical current in the Bi-Sr-Ca-Cu-O system using a glassy phase

    International Nuclear Information System (INIS)

    Several research centres have started at the same time investigations of the concept of homogeneous HTSC using the initial composition in the form of a glassy matrix. Initially, this was applied to the HTSC in the Bi-Sr-Ca-Cu-O system as a result of the high glass-forming capacity of Bi2O3 in the presence of bivalent cations. In this work, we generalise the main results obtained in the synthesis and properties of the superconducting phases in the Bi-Sr-Ca-Cu-O system using, as the intermediate half product, the glassy phase in this system with the molar ratio of the cations 2:2:1:2 and 2:2:2:3

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. High-temperature superconductivity

    International Nuclear Information System (INIS)

    After a short account of the history of experimental studies on superconductivity, the microscopic theory of superconductivity, the calculation of the control temperature and its possible maximum value are presented. An explanation of the mechanism of superconductivity in recently discovered superconducting metal oxide ceramics and the perspectives for the realization of new high-temperature superconducting materials are discussed. 56 refs, 2 figs, 3 tabs

  3. 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.

  4. 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.

  5. Enhanced dielectric and ferroelectric properties of Ba and Ti co-doped BiFeO3 multiferroic ceramics

    International Nuclear Information System (INIS)

    Highlights: • The structural phase transition with increasing Ti content was confirmed. • The reduction of low frequency dispersion in dielectric constant with Ti content. • With increasing Ti content the ferroelectricity was gradually improved. • Variation of the ferroelectric hysteresis loop induced by magnetic polarization. -- Abstract: Multiferroic ceramics Bi0.8Ba0.2Fe1−xTixO3 with x = 0, 0.1 and 0.2 were prepared by using the conventional solid state reaction method. The structural, dielectric, ferroelectric and magnetic properties were investigated. The structure phase transition from rhombohedral to tetragonal with increasing the Ti substitution concentration was confirmed using X-ray diffraction. The reduction of low frequency dispersion in the dielectric constant and loss with an increase in the Ti content was observed. The ferroelectric measurements revealed that the leakage current is significantly suppressed with Ti substitution. Magnetic hysteresis loops showed a continuous decrease in magnetization with Ti substitution, which can be attributed to the collinear antiferromagnetic spin structure in tetragonal structure. In addition, a remarkable change in the polarization and ferroelectric loop area after poling the samples in the dc magnetic field indicates the presence of magnetoelectric coupling at room temperature

  6. RVB States in doped Band Insulators from Coloumb forces: Theory and a case study of Superconductivity in BiS$_2$ Layers

    OpenAIRE

    G. Baskaran

    2016-01-01

    Doped band insulators, HfNCl, WO$_3$, diamond, Bi$_2$Se$_3$, \\bis2 families, STO/LAO interface, gate doped SrTiO$_3$ and MoS$_2$ etc. are unusual superconductors. With an aim to build a general theory for superconductivity in doped band insulators we focuss on \\bis2 family, discovered by Mizuguchi et al. in 2012. While maximum Tc is only $\\sim$ 11 K in \\laofx, a number of experimental results are puzzling and anomalous; they resemble high Tc and unconventional superconductors. Using a two orb...

  7. Influence of delamination location on mesoscopic stress state and critical current under bending deformation in Bi2223/Ag superconducting composite tapes

    Energy Technology Data Exchange (ETDEWEB)

    Hojo, M. [Department of Mechanical Engineering, Kyoto University, Kyoto 606-8501 (Japan)]. E-mail: hojo_cm@mech.kyoto-u.ac.jp; Nakamura, M. [Department of Mechanical Engineering, Kyoto University, Kyoto 606-8501 (Japan); Tanaka, M. [Department of Mechanical Engineering, Kyoto University, Kyoto 606-8501 (Japan); Adachi, T. [Department of Mechanical Engineering, Kyoto University, Kyoto 606-8501 (Japan); Sugano, M. [Department of Electronic Science and Engineering, Kyoto University, Kyoto 615-8510 (Japan); Ochiai, S. [International Innovation Center, Kyoto University, Kyoto 606-8501 (Japan); Osamura, K. [Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501 (Japan)

    2005-10-01

    The strain dependence of the critical current, I {sub c}, of Bi2223/Ag/Ag-alloy composite superconducting tapes has been studied both experimentally and analytically under bending deformation. The microscopic observation after bending deformation indicated that delamination existed inside Bi2223 filaments and filament/matrix interface. Then, the former bending deformation analysis was modified to fit the existence of the delamination. The calculated critical current, I {sub c}, was almost the same as the experimental results when the delamination is fully located at the mid plane of the tape though the actual situation was partial in the width direction. Then the location of the delamination was moved in the thickness direction in the analysis. The calculated I {sub c} agreed well with the experimental results when the delamination location was moved to the compressive side.

  8. Modeling of the bending strain dependence of the critical current in Bi2223/Ag composite tapes based on the damage stress of the superconducting filament

    Science.gov (United States)

    Gou, Xiaofan; Shen, Qiang

    2012-05-01

    An analysis model of the bending strain dependence of the critical current in multifilamentary Bi2223/Ag composite tapes is presented. To investigate the effect of the mechanical properties of the Bi2223 superconducting filament, the actual part for carrying current, its damage stress and elastic modulus are introduced. The calculated result of the variation of the critical current with the bending strain is well agreed with the experimental one. The further studies find that the mechanical properties of the filament have a remarkable effect on the bending strain dependence of the critical current. Specifically, the larger the damage stress and elastic modulus of the filament are, the higher the critical current is, when the bending strain increases to a larger value beyond the critical one.

  9. Modeling of the bending strain dependence of the critical current in Bi2223/Ag composite tapes based on the damage stress of the superconducting filament

    Energy Technology Data Exchange (ETDEWEB)

    Gou Xiaofan, E-mail: xfgou@hhu.edu.cn [Department of Engineering Mechanics, Hohai University, Nanjing, Jiangsu 210098 (China); Shen Qiang [Department of Engineering Mechanics, Hohai University, Nanjing, Jiangsu 210098 (China)

    2012-05-15

    An analysis model of the bending strain dependence of the critical current in multifilamentary Bi2223/Ag composite tapes is presented. To investigate the effect of the mechanical properties of the Bi2223 superconducting filament, the actual part for carrying current, its damage stress and elastic modulus are introduced. The calculated result of the variation of the critical current with the bending strain is well agreed with the experimental one. The further studies find that the mechanical properties of the filament have a remarkable effect on the bending strain dependence of the critical current. Specifically, the larger the damage stress and elastic modulus of the filament are, the higher the critical current is, when the bending strain increases to a larger value beyond the critical one.

  10. 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.

  11. Characterization of the BaBiO3-doped BaTiO3 positive temperature coefficient of a resistivity ceramic using impedance spectroscopy with Tc=155℃

    Institute of Scientific and Technical Information of China (English)

    Yuan Chang-Lai; Liu Xin-Yu; Zhou Chang-Bong; Xu Ji-Wen; Yang Yun

    2011-01-01

    BaBi03-doped BaTi03 (BB-BT)ceramic, as a candidate for lead-free positive temperature coefficient of resistivity (PTCR)materials with a higher Curie temperature, has been synthesized in air by a conventional sintering technique.The temperature dependence of resistivity shows that the phase transition of the PTC thermistor ceramic occurs at the Curie temperature, Tc=155℃, which is higher than that of BaTiO3 (≤130℃). Analysis of ac impedance data using complex impedance spectroscopy gives the alternate current (AC)resistance of the PTCR ceramic. By additional use of the complex electric modulus formalism to analyse the same data, the inhomogeneous nature of the ceramic may be unveiled. The impedance spectra reveal that the grain resistance of the BB-BT sample is slightly influenced by the increase of temperature, indicating that the increase in overall resistivity is entirely due to a grain-boundary effect.Based on the dependence of the extent to which the peaks of the imaginary part of electric modulus and impedance are matched on frequency, the conduction mechanism is also discussed for a BB-BT ceramic system.

  12. Evidence for interfacial superconductivity in a bi-collinear antiferromagnetically ordered FeTe monolayer on a topological insulator

    OpenAIRE

    Manna, Sujit; Kamlapure, Anand; Cornils, Lasse; Hänke, Torben; Hedegaard, Ellen Marie Jensen; Bremholm, Martin; Iversen, Bo Brummerstedt; Hofmann, Philip; Wiebe, Jens; Wiesendanger, Roland

    2016-01-01

    The discovery of high-temperature superconductivity in Fe-based compounds [1,2] has triggered numerous investigations on the interplay between superconductivity and magnetism [3] and, more recently, on the enhancement of transition temperatures through interface effects [4]. 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 of this relationship remain...

  13. 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).

  14. 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.)

  15. 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.

  16. 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...... instabilities predicted for the rf-SQUID inductance mode were observed. These signal instabilities may be exploited to enhance the transfer coefficient for measured flux-to-output signal. Journal of Applied Physics is copyrighted by The American Institute of Physics....

  17. Effect of structural transition on magnetic and dielectric properties of La and Mn co-substituted BiFeO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Pawan; Kar, Manoranjan, E-mail: mano@iitp.ac.in

    2014-12-15

    Bi{sub 1−x}La{sub x}Fe{sub 1−x}Mn{sub x}O{sub 3} (x = 0.000–0.300) ceramics prepared by the tartaric acid modified sol–gel technique have been studied to analyze the effect of composition driven structural transition on the magnetic properties of bismuth ferrite (BiFeO{sub 3}). It was found that the co-substitution of La and Mn at Bi and Fe sites leads to suppression of impurity phases (Bi{sub 2}Fe{sub 4}O{sub 9} and Bi{sub 25}FeO{sub 40}) which generally appear in BiFeO{sub 3}. The quantitative crystallographic phase analysis has been carried out by double phase Rietveld analysis of all the XRD patterns which indicates the existence of compositional driven crystal structure transformation from rhombohederal (space group R3c) to the orthorhombic (space group Pbnm) with the increase in substitution concentration. The 5% co-substituted sample exhibit high remnant magnetization i.e. about 15 times that of BiFeO{sub 3} which is due to the suppression of cycloid spin structure and enhanced canting angle of antiferromagnetically ordered spins caused by the crystal lattice distortion. However, further increase in substitution results in the reduction of remnant magnetization and coercivity due to the appearance of complete antiferromagnetic ordering in the orthorhombic structure because of the significant contribution from the crystallographic phase of Pbnm space group (as obtained from double phase Rietveld analysis). The frequency independent higher dielectric constant and lower dielectric loss were observed for 5% co-substitution. Hence, this particular composition may be interesting for device applications. - Graphical abstract: Rietveld refined XRD patterns of Bi{sub 0.950}L{sub 0.050}Fe{sub 0.950}Mn{sub 0.050}O{sub 3} sample. The two rows of Bragg positions are for R3c and Pbnm space groups respectively and corresponding wt% of crystallographic phases have been quantified using this refinement. - Highlights: • Secondary phase formation has been

  18. Amorphous superconducting transformation in bismuth-base high-{Tc} superconducting rods

    Energy Technology Data Exchange (ETDEWEB)

    Khan, M.N. [Univ. of Bahrain (Bahrain); Ul Haq, A. [Dr. A.Q. Khan Research Labs., Rawalpindi (Pakistan). Metallurgy Div.

    1996-08-01

    The transformation of high-resistivity amorphous (Bi{sub 1.68}Pb{sub 0.32})Sr{sub 1.75}Ca{sub 1.85}Cu{sub 2.85}O{sub y} and (Bi{sub 1.6}Pb{sub 0.4})Sr{sub 1.7}Ca{sub 2.3}Cu{sub 3}O{sub y} to superconductive materials has been characterized by structural, thermochemical, transport, and scanning electron microscope measurements. X-ray powder diffraction confirmed that rapid solidification of Bi-Pb-Sr-Ca-Cu-O{sub y} yields amorphous material. In further heat treatments, sequential crystallization of three phases was identified. Differential scanning calorimetry indicated an exothermic crystallization peak at 520 C with corresponding enthalpy of 62 J/g. Scanning electron microscopy studies revealed that the grain size increases with sintering time and that the formation mechanism in the interior of the bulk is different from that at the surface of the superconducting glass ceramic rods. Thermal cycling of the insulating glass to a temperature above that required for crystallization results in a transformation from an insulating to a superconducting material with a {Tc} (R = 0) of 105 K. It was also shown that the glass ceramic rods obtained by reheating glass rods to 850 C for 120 h have a {Tc} (R = 0) of 105 K, whereas the disk specimens obtained by reheating the powered glass compacts in the same way do not exhibit superconductivity above 85 K. This difference in superconductivity between the specimens is discussed in terms of the crystallization process and the amount of oxygen absorption of the specimens during heating.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Effect of La-substitution on the structure, dielectric and ferroelectric properties of Nb modified SrBi{sub 8}Ti{sub 7}O{sub 27} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Parida, Geetanjali, E-mail: geeta.lily@gmail.com; Bera, J., E-mail: jbera@nitrkl.ac.in

    2015-08-15

    Graphical abstract: The ferroelectric properties of Nb modified Bi{sub 4}Ti{sub 3}O{sub 12}–SrBi{sub 4}Ti{sub 4}O{sub 15} intergrowth ceramics increases significantly when Bi is substituted by La. - Highlights: • La{sup 3+} substitution for Bi{sup 3+} in Nb doped Bi{sub 4}Ti{sub 3}O{sub 12}–SrBi{sub 4}Ti{sub 4}O{sub 15} ferroelectrics is reported. • The orthorhombic distortion of the structure decreased with the increasing La. • La acts as a grain growth inhibitor in the ceramics. • The remnant polarization of the ferroelectrics increased significantly with La substitution. - Abstract: The effect of La substitution on the electrical properties of SrLa{sub x}Bi{sub 8−x}Ti{sub 6.88}Nb{sub 0}.{sub 12}O{sub 27} intergrowth Aurivillius phase ferroelectric ceramic was investigated. La content ‘x’ was ranging from 0.0 to 1.0 in a step of 0.2. The ceramic phase was synthesized through a modified oxalate route. X-ray diffraction was used to identify the phase and to investigate the change in lattice parameter and microstrain with the substitution. La-substitution does not affect the crystal structure of the intergrowth. Microstructural investigation revealed that the grain size of the ceramic decreases with La addition. The lattice parameters and orthorhombicity of intergrowth structure were found to decrease with increasing La substitution. The temperature dependence of dielectric behavior was investigated in the temperature range 30–700 °C and the frequency of 100 kHz. The remnant polarization 2P{sub r} increased and the Curie temperature T{sub c} decreased with the increase in the La substitution.

  4. 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 .

  5. 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/℃.

  6. 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.

  7. Structural and superconducting properties of isoelectronic Sb-substituted Ba sub 1-x K sub x BiO sub 3

    Energy Technology Data Exchange (ETDEWEB)

    Dabrowski, B.; Peng Weimin; Melim, V.; Kimball, C.W. (Northern Illinois Univ., DeKalb (United States)); Pei Shiyou; Richards, D.R.; Zheng, Y.; Jorgensen, J.D.; Hinks, D.G.; Mitchell, A.W.; Dunlap, B.D. (Materials Sciences Div., Argonne National Lab., IL (United States))

    1992-02-01

    Single phase samples of (Ba{sub 1-x}K{sub x}) (Bi{sub 1-y}Sb{sub y})O{sub 3} have been synthesized over a limited compositional range using a two-step procedure: high-temperature firing in a low oxygen partial pressure followed by a low-temperature oxygen annealing. For y>0 samples are superconducting only in a simple cubic structure with Tc gradually decreasing as y increases for fixed x. As in the case of potassium only (y=0) substituted material, the highest Tc is found in the compositional range adjacent to the structural phase transition into the lower symmetry nonsuperconducting phase. Moessbauer effect measurements indicate that Sb is close to +5 valent state with small mixed valent behavior which increases with Sb content. (orig.).

  8. High critical current silver-Bi2Sr2CaCu2O8-x superconducting multilayer ribbons produced by rolling

    International Nuclear Information System (INIS)

    Multilayer ribbons have been fabricated from 0.004 in. thick silver strips, coated with Bi-2212 powder. After stacking and sealing in an evacuated silver box and cold-rolling to a 0.023 in. thick sandwich, very encouraging superconductive behavior has been observed. At 4.2 K such a ribbon carried critical currents of 200 A and 100 A, respectively, in fields of 0 T and 2.8 T, correspond to current density values of 4.2 x 104 A/cm2 and 2.1 x 104A/cm2; at 77 K the current decreased to 2.5 A in zero field. Considerable grain alignment in the superconductor was noted close to the silver sheath in ribbons with these results

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

    International Nuclear Information System (INIS)

    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 fabricated using precursor powders containing different Pb-rich phases. Sintering was carried out at a fixed temperature of 830 deg. C in 8.5% O2. The phase transitions, structure changes and texture evolution in (Bi,Pb)-2223/Ag tapes were carefully analyzed, and the evolution of different Pb-rich phases, such as Ca2PbO4 and Pb3Sr2.5Bi0.5Ca2CuOy (3321), was discussed. It was found that tapes fabricated using the precursor with the (Bi,Pb)-2212 phase exhibited higher (Bi,Pb)-2223 formation rate than tapes fabricated using the precursors with Pb-rich phases. Texture evolution indicates that texture of the (Bi,Pb)-2212 phase formed in the thermomechanical process depends strongly on the Pb-rich phases of the precursor powders, while the texture of the new formed (Bi,Pb)-2223 grains for all three tapes follows the texture of (Bi,Pb)-2212 grains, and the final (Bi,Pb)-2223 and (Bi,Pb)-2212 textures are approximately identical. A higher texture degree of (Bi,Pb)-2223 grains was achieved in tapes fabricated using the precursors with 3321 or Ca2PbO4 phases.

  10. Quantitative phase separation in multiferroic Bi0.88Sm0.12FeO3 ceramics via piezoresponse force microscopy

    International Nuclear Information System (INIS)

    BiFeO3 (BFO) is a classical multiferroic material with both ferroelectric and magnetic ordering at room temperature. Doping of this material with rare-earth oxides was found to be an efficient way to enhance the otherwise low piezoelectric response of unmodified BFO ceramics. In this work, we studied two types of bulk Sm-modified BFO ceramics with compositions close to the morphotropic phase boundary (MPB) prepared by different solid-state processing methods. In both samples, coexistence of polar R3c and antipolar Pbam phases was detected by conventional X-ray diffraction (XRD); the non-polar Pnma or Pbnm phase also has potential to be present due to the compositional proximity to the polar-to-non-polar phase boundary. Two approaches to separate the phases based on the piezoresponse force microscopy measurements have been proposed. The obtained fractions of the polar and non-polar/anti-polar phases were close to those determined by quantitative XRD analysis. The results thus reveal a useful method for quantitative determination of the phase composition in multi-phase ceramic systems, including the technologically most important MPB systems

  11. Terahertz emission from Bi2Sr2CaCu2O8+δ intrinsic Josephson junction stacks with all-superconducting electrodes

    Science.gov (United States)

    Yuan, J.; Li, M. Y.; Li, J.; Gross, B.; Ishii, A.; Yamaura, K.; Hatano, T.; Hirata, K.; Takayama-Muromachi, E.; Wu, P. H.; Koelle, D.; Kleiner, R.; Wang, H. B.

    2012-07-01

    Terahertz (THz) emission has been recently detected from intrinsic Josephson junction (IJJ) stacks made of the high critical temperature superconductor Bi2Sr2CaCu2O8+δ (BSCCO). The most employed structure is a mesa standing on a big pedestal of a single crystal with a thin gold layer as its top electrode. In this work, a large (300 × 50 × 1.2 μm3) IJJ stack with superconducting electrodes was fabricated and studied. The stack consisted of N ≈ 800 IJJs. It was prepared with a double-sided fabrication process, and significant THz emission was detected. The output power is comparable to the emission power detected from mesa structures, obviously not weakened by the superconducting upper electrode. The observation of THz emission from the double-sided structure suggests that off-chip THz emission from IJJs can be obtained not only from mesa structures and, most importantly, that the emission power can be potentially enhanced in integrated multi-stack radiation sources.

  12. Structural evolution and physical properties of multiferroic Bi0.9−xLa0.1PbxFeO3−x/2 ceramics

    International Nuclear Information System (INIS)

    The polycrystalline samples of multiferroic Bi0.9−xLa0.1PbxFeO3−x/2 (x = 0–0.35) were prepared by the solid state reaction method and characterized by x-ray diffraction, field emission scanning electron microscopy, dielectric, magnetic, magnetodielectric (MD) and magnetoelectric (ME) measurements. A structural evolution from rhombohedral to pseudocubic structure was found to happen near x = 0.20. The changes and anomalies observed in magnetization were correlated with structural evolution and the development in microstructure. The ferroelectromagnetic measurements demonstrated Pb2+ doping to be a very effective method to realize the coexistence of weak ferromagnetism and ferroelectric in the ferroelectric R3c phase of BiFeO3. The MD and ME effects of Bi0.9−xLa0.1PbxFeO3−x/2 ceramics were first reported. A maximum ME voltage coefficient has been observed at x = 0.30. This work is helpful for understanding the ferroelectromagnetic behaviors and ME effect with complicated spin structures. (paper)

  13. Effect of structural transition on magnetic and optical properties of Ca and Ti co-substituted BiFeO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Pawan; Kar, Manoranjan, E-mail: mano@iitp.ac.in

    2014-01-25

    Highlights: • Secondary phase formation has been controlled for Bi{sub 0.9}Ca{sub 0.1}Fe{sub 0.9}Ti{sub 0.1}O{sub 3} • Co-substitution of Ca and Ti at Bi and Fe sites significantly increases M{sub S} and H{sub C} • Compositional driven structural transition from rhombohedral to orthorhombic symmetry. • The leakage current has reduced significantly for Ca{sup 2+} and Ti{sup 4+} co-substituted BiFeO{sub 3}. • Small band gap of co-substituted BiFeO{sub 3} may be useful for optoelectronic devices. -- Abstract: Bi{sub 1−x}Ca{sub x}Fe{sub 1−x}Ti{sub x}O{sub 3} ceramics with x = 0.0, 0.05, 0.075, 0.10, 0.125, 0.15 and 0.2 nanoparticles were prepared by the tartaric acid modified sol–gel technique. The co-substitution of Ca and Ti in certain proportion controls the formation of secondary phases. Structural phase analysis by XRD suggested that pure bismuth ferrite stabilized in rhombohedral crystal symmetry (space group R3c) and orthorhombic (Pbnm) phase fraction was observed in co-substituted samples which increase with the increase in substitution percentage. The changes in the phonon frequencies (A{sub 1}) and line widths in Raman spectra reveal the lattice distortion in co-substituted samples which are in agreement with our XRD analysis. The improved magnetization and coercive field in co-substituted samples occurs due to the suppression of cycloid spin structure which could be explained in terms of field induced spin reorientation and weak ferromagnetism. The Ti{sup 4+} substitution at Fe site in BiFeO{sub 3} significantly reduced the oxygen vacancies and hence the associated leakage current, which leads to the increase of dielectric constant as well as frequency independent region for ∊{sub r} and tan δ (maximum in Bi{sub 0.85}Ca{sub 0.15}Fe{sub 0.85}Ti{sub 0.15}O{sub 3}). The significant decrease in dielectric loss with the increase in substitution percentage leads to the decrease in the room temperature bulk conductivity and thus enhanced

  14. 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.

  15. Analysis of mesoscopic stress states with delamination and their relation to critical current under bending deformation in Bi2223/Ag superconducting composite tapes

    Energy Technology Data Exchange (ETDEWEB)

    Hojo, Masaki [Department of Mechanical Engineering and Science, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan); Nakamura, Mitsuhiro [Department of Mechanical Engineering and Science, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan); Tanaka, Mototsugu [Department of Mechanical Engineering and Science, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan); Adachi, Taiji [Department of Mechanical Engineering and Science, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan); Sugano, Michinaka [Department of Electric Science and Engineering, Kyoto University, Kyoto 615-8510 (Japan); Ochiai, Shojiro [International Innovation Center, Kyoto University, Kyoto 606-8501 (Japan); Osamura, Kozo [Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501 (Japan)

    2005-12-15

    The mesoscopic stress and strain states of Bi2223/Ag/Ag-alloy superconducting composite tapes have been studied both analytically and experimentally under bending deformation. The tapes used in the present study were supplied as the standard samples for the VAMAS round-robin program (classified as VAM1 and VAM3). Detailed tape bending analysis was completed based on a damage-free initial state, and the calculated decrease of critical current, I{sub c}, due to Bi2223 filament fracture was compared to the experimental I{sub c} decrease. The calculated I{sub c} was much lower than that obtained in the experiments for both tapes. Metallography indicated the presence of delamination in as-received as well as bend-tested tapes. The analysis was therefore modified to include delamination and it was completed for the case where delamination occupied the full width of the tape mid-plane. The calculated I{sub c} with delamination was higher than the experimental results for both tapes. Delamination occupying partial width of the mid-plane explained this difference. Finally, the width ratio where delamination exists was calculated by comparing the analytical results with delamination and experimental results. This ratio increased with increasing curvature of the tape.

  16. Experimental and numerical investigation of dielectric resonator antenna based on the BiFeO{sub 3} ceramic matrix added with Bi{sub 2}O{sub 3} or PbO

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, H.O., E-mail: herbertrodrigues@fisica.ufc.br [Departamento de Engenharia de Teleinformática, Universidade Federal do Ceará, Caixa Postal 6007, CEP 60755-640, Fortaleza, Ceará (Brazil); Laboratório de Telecomunicações e Ciência e Engenharia dos Materiais (LOCEM), Universidade Federal do Ceará, Caixa Postal 6030, CEP 60455-760, Fortaleza, Ceará (Brazil); Sales, A.J.M.; Pires Junior, G.F.M. [Departamento de Engenharia de Teleinformática, Universidade Federal do Ceará, Caixa Postal 6007, CEP 60755-640, Fortaleza, Ceará (Brazil); Laboratório de Telecomunicações e Ciência e Engenharia dos Materiais (LOCEM), Universidade Federal do Ceará, Caixa Postal 6030, CEP 60455-760, Fortaleza, Ceará (Brazil); Almeida, J.S.; Silva, M.A.S.; Sombra, A.S.B. [Laboratório de Telecomunicações e Ciência e Engenharia dos Materiais (LOCEM), Universidade Federal do Ceará, Caixa Postal 6030, CEP 60455-760, Fortaleza, Ceará (Brazil)

    2013-11-05

    Highlights: •We make an experimental and numerical study of the MW properties of BiFeO{sub 3} matrix. •The materials were obtained in a known route in the solid state procedure. •The experimental and theoretical results of the resonators are in good agreement. •The addition of lead oxide deteriorated the thermal stability of the ceramic. •The results confirm the potential use of these materials for small DRAs. -- Abstract: In this paper is reported an experimental and numerical investigation of the microwave dielectric properties of BiFeO{sub 3} (BFO) ceramic matrix added with 3 and 10 wt% of Bi{sub 2}O{sub 3} or PbO, obtained through a new procedure based on the solid-state method. The experimental and theoretical characteristics of the resonator like return loss, bandwidth, input impedance are in good agreement. The simulations of radiation patterns are presented. For BFO reference sample, frequency response bandwidth is of 6.40% (simulated) and 7.18% (experimental) for frequency operation around 2.94 GHz. The BFO reference sample showed a dielectric permittivity around 25, with loss around 10{sup −2}. The adding of bismuth oxide (3 and 10 wt%) reduced the value of the dielectric permittivity as well as lead oxide 3 wt%, otherwise only the adding of 10 wt% increases its value. The temperature coefficient of resonant frequency (τ{sub f}) was also measured for all dielectric samples. The values obtained were in the range of −517 ppm °C{sup −1} to −222 ppm °C{sup −1}. With the addition of lead oxide was observed a deterioration of the thermal stability of the ceramic, with respect to the central frequency of resonance. The results obtained confirm the necessity of producing composites of this material with others positive τ{sub f} materials for obtaining dielectric resonator antennas with τ{sub f} ∼ 0.

  17. 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).

  18. 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)

  19. Giant strain with low cycling degradation in Ta-doped [Bi1/2(Na0.8K0.2)1/2]TiO3 lead-free ceramics

    Science.gov (United States)

    Liu, Xiaoming; Tan, Xiaoli

    2016-07-01

    Non-textured polycrystalline [Bi1/2(Na0.8K0.2)1/2](Ti1-xTax)O3 ceramics are fabricated and their microstructures and electrical properties are characterized. Transmission electron microscopy reveals the coexistence of the rhombohedral R3c and tetragonal P4bm phases in the form of nanometer-sized domains in [Bi1/2(Na0.8K0.2)1/2]TiO3 with low Ta concentration. When the composition is x = 0.015, the electrostrain is found to be highly asymmetric under bipolar fields of ±50 kV/cm. A very large value of 0.62% is observed in this ceramic, corresponding to a large-signal piezoelectric coefficient d33* of 1240 pm/V (1120 pm/V under unipolar loading). These values are greater than most previously reported lead-free polycrystalline ceramics and can even be compared with some lead-free piezoelectric single crystals. Additionally, this ceramic displays low cycling degradation; its electrostrain remains above 0.55% even after undergoing 10 000 cycles of ±50 kV/cm bipolar fields at 2 Hz. Therefore, Ta-doped [Bi1/2(Na0.8K0.2)1/2]TiO3 ceramics show great potential for large displacement devices.

  20. 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.

  1. 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.

  2. Role of the Ce valence in the coexistence of superconductivity and ferromagnetism of CeO$_{1-x}$F$_{x}$BiS$_{2}$ revealed by Ce $L_3$-edge x-ray absorption spectroscopy

    OpenAIRE

    Sugimoto, Takuya; Joseph, Boby; Paris, Eugenio; Iadecola, Antenolla; Mizokawa, Takashi; Demura, Satoshi; Mizuguchi, Yoshikazu; Takano, Yoshihiko; Saini, Naurang L.

    2014-01-01

    We have performed Ce $L_3$-edge x-ray absorption spectroscopy (XAS) measurements on CeO$_{1-x}$F$_x$BiS$_2$, in which the superconductivity of the BiS$_2$ layer and the ferromagnetism of the CeO$_{1-x}$F$_x$ layer are induced by the F-doping, in order to investigate the impact of the F-doping on the local electronic and lattice structures. The Ce $L_3$-edge XAS spectrum of CeOBiS$_2$ exhibits coexistence of $4f^1$ (Ce$^{3+}$) and $4f^0$ (Ce$^{4+}$) state transitions revealing Ce mixed valency...

  3. 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.

  4. 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.

  5. Synthesis, electrical and thermal properties of Bi4V2-xZrxO11 (x=0.0 and 0.06) ceramics

    International Nuclear Information System (INIS)

    Polycrystalline ceramic samples of Bi4V2-xZrxO11 (x=0.0 and 0.06) have been synthesized by standard solid state reaction method. The formation of the compounds has been verified by room temperature (RT) X-ray diffraction analysis. The frequency and temperature dependent dielectric constant of both the compounds have been measured. The dielectric studies indicate that the materials are highly lossy. The dc conductivity of the materials has been measured as a function of temperature from RT to 653K and their activation energies were calculated using Arrhenius relation σ = σoexp(-Ea/kT). The heat capacity and heat flow of both the compounds were determined as a function of temperature using Modulated Differential Scanning Calorimetry (MDSC). (author)

  6. 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.

  7. 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.

  8. Ferroelectric Phase Transition and Photoinduced Cooperative Phenomena in Bi-Layered Perovskite Pb2Bi4Ti5O18 Ceramics Studied by Brillouin Scattering

    Science.gov (United States)

    Takesada, Masaki; Ueki, Ayaka; Onodera, Akira; Noguchi, Yuji; Miyayama, Masaru

    2010-09-01

    The ferroelectric phase transition mechanism and ultraviolet (UV) photoexcition effect have been investigated in the bismuth layered perovskite Pb2Bi4Ti5O18 by Brillouin scattering using a Sandercock-type tandem Fabry-Perot interferometer. The temperature dependences of Brillouin spectra both with and without UV irradiation were observed around phase transition points. The observed Brillouin spectra include a central peak component that shows an anomaly in the ferroelectric phase transition point TC=450 K. The central peak spectra show narrowing under UV irradiation. The correlation length of the ferroelectric dipole fluctuation should be enhanced with the UV irradiation effect below TC.

  9. 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.

  10. Relaxor Behavior and Dielectric Properties of Bi(Zn2/3Nb1/3)O3-Modified BaTiO3 Ceramics

    Science.gov (United States)

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

    2015-12-01

    (1 - x)BaTiO3- xBi(Zn2/3Nb1/3)O3 [(1 - x)BT- xBZN, 0 ≤ x ≤ 0.2] ceramics were prepared via a conventional solid-state reaction method. X-ray diffraction (XRD) patterns and Raman spectra analysis show that the ceramics are tetragonal phase when x ≤ 0.02, and transform to pseudocubic phase as x ≥ 0.06. The temperature and frequency dependences of relative permittivity indicate a gradual crossover from a classic ferroelectric to relaxor ferroelectric. The dielectric relaxor behavior follows a modified Curie-Weiss law. The degree of the phase transition diffuseness ( γ) and the deviation from the Curie-Weiss law (Δ T_{{d}} ) increase to the maximum at x = 0.08, and subsequently decrease with further increasing x values, which associated with the appearance of polar nanoregions on account of the formation of random fields included local electric fields and elastic fields. Nevertheless, the random fields may decrease by reason of the interaction between the local electric fields and elastic fields.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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...

  17. Microstructural properties of Bi1.65Pb0.35Sr2Ca2Cu3O10+δ and Bi1.65Pb0.35Sr2CaCu2O8+δ ceramic samples through transport measurements: a comparative study

    International Nuclear Information System (INIS)

    We have studied in detail the dependence of the electrical resistivity as a function of temperature of Bi1.65Pb0.35Sr2Ca2Cu3O10+δ((Bi,Pb)-2223) and Bi 1.65Pb 0.35Sr 2CaCu 2O 8+δ ((Bi,Pb)-2212) ceramic samples. Both types of samples were obtained by a solid-state reaction method and pressed uniaxially at different compacting pressures ranging from 90 to 600 MPa before the last heat treatment. From electrical resistivity measurements as a function of temperature, we were able to separate contributions arising from both the grains' misalignment and microstructural defects, by using a current-conduction model. The results suggest that in both compounds the texture degree and the connectivity between grains are improved with increasing compacting pressures. It was found that in the (Bi,Pb)-2223 samples, even in those obtained at low compacting pressures, the grains exhibit a preferential orientation. A similar effect, but less pronounced, was observed in the (Bi,Pb)-2212 samples. In both cases, the behavior is different to the one reported in YBCO ceramic samples, in which the grains exhibit random orientation. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Momentum-resolved ultrafast electron dynamics in superconducting Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Rettig, L. [Fachb. Physik, Freie Univ. Berlin (Germany); Fak. f. Physik, Univ. Duisburg-Essen, Duisburg (Germany); Cortes, R. [Fachb. Physik, Freie Univ. Berlin (Germany); Abt. Phys. Chemie, Fritz-Haber-Institut d. MPG, Berlin (Germany); Yoshida, Y.; Eisaki, H. [Nat. Inst. of Adv. Industrial Science and Technology, Tsukuba, Ibaraki (Japan); Wolf, M. [Abt. Phys. Chemie, Fritz-Haber-Institut d. MPG, Berlin (Germany); Bovensiepen, U. [Fak. f. Physik, Univ. Duisburg-Essen, Duisburg (Germany)

    2011-07-01

    The processes responsible for the relaxation of hot quasiparticles (QPs) in high-T{sub c} superconductors have been intensely studied by time-resolved optical and THz spectroscopy. These studies conclude on highly momentum dependent dynamics, which however cannot be resolved directly by these momentum integrating techniques. Here, we report on the non-equilibrium state of the high-T{sub c} superconductor Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} and its ultrafast dynamics investigated by femtosecond time- and angle-resolved photoemission spectroscopy. This technique allows direct investigation of excited QPs and the dynamics of the superconducting state with both momentum and energy resolution. Thus, we are able to investigate optically excited QPs at different electron momenta along the Fermi surface and detect metastable QPs near the antinode. Their decay through e-e scattering is blocked by a scattering phase space restricted to the nodal region. We find a single exponential relaxation of the excited QPs with momentum independent decay rates, in agreement with relaxation dominated by Cooper pair recombination in a boson bottleneck limit.

  19. 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 electrode compatibility suggest that the developed materials can be used in low temperature co-fired multilayer capacitor applications.

  20. Anisotropic superconducting properties and fabrication of submicrometre bridges in misaligned Bi-Sr-Ca-Cu-O (2212) films

    CERN Document Server

    Moriya, M; Usami, K; Goto, T; Kobayashi, T

    2002-01-01

    In this paper, we report on misaligned Bi-Sr-Ca-Cu-O (2212) films that have been deposited on vicinal strontium titanate substrates using a dc sputtering system. We measured the temperature dependences of resistivity across and along the terrace, and only the resistivity across the terrace slightly decreased with the increase of the temperature in the normal state region. The estimated anisotropy parameter gamma was smaller than that of single crystal, but a significant anisotropy was observed. Submicrometre bridges were fabricated, and the temperature dependence of the critical current density was investigated. The value of the critical current density across the terrace is smaller than the value of that along the terrace. This suggests that the current partially flows along the c-axis. However, a multi-branch structure was not observed even after post annealing in oxygen atmosphere at low pressure.

  1. The Mercereau effect as a guide to the theory of high-Tc superconductivity in rare earth oxide ceramics

    International Nuclear Information System (INIS)

    We emphasize the importance of performing definite experiments on quantum interferometers, basing our work on a phenomenological theory of high-Tc superconductivity co-existing with antiferromagnetism. The theory satisfies all the general requirements of previous models, including minimal gauge invariant coupling terms. Yet, since no doping-dependent displacements are implied in the Mercereau diffraction pattern, this phenomenological approach underlines the urgency of performing new experiments in order to guide the theory. (author). 21 refs, 1 fig

  2. (Cu,Tl)Ba2Ca3Cu4Ox compositions: II. Heating rate applied to synthesis of superconducting ceramics

    International Nuclear Information System (INIS)

    Superconducting samples with a starting composition Cu0.5TlxBa2Ca3Cu4O12 (x=1-0.35) were prepared in Au tubes from oxides by using different heating rates. The optimum heating rate was 0.11 deg. C min-1 applied between 860 and 880 deg. C. These samples show the highest content of 1234 phase and the lowest of Ba-Cu-O phases as well as the highest critical temperatures. The highest values were Tc=119.2 K and Tc0=115.1 K. All samples show Jc values around 6x105 A cm-2, at 60 K and 0.5 T. In the rest of the samples, heated by using lower or higher heating rates, a high concentration of 1223 and/or 1245 phases is detected. The content of the 1234 phase and of Ba(Ca,Tl)-Cu-O residual liquid phase, in the samples synthesized for the optimum heating rate, depends on the Tl content in the starting mixture. The influence of the oxygen content in the starting mixture on phase composition is not as strong as of Tl, but it has a major role in establishing the superconducting behaviour of the 1234 grains. Some arguments that suggest the dependence of the transport properties of the non-superconducting matrix on oxygen content will be discussed. In our technological arrangement the determined optimum heating rate can be applied to the synthesis of other single-layered superconducting phases, e.g. 1212 phase from a Cu0.25Tl0.75Ba2CaCu2O8.115 starting composition. (author)

  3. YBa2SnO5.5, a novel ceramic substrate for YBCO and BiSCCO superconductors

    International Nuclear Information System (INIS)

    YBa2SnO5.5 has been synthesized and sintered as single phase material for its use as substrate for both YBCO and BiSCCO superconductors. YBa2SnO5.5 has a complex cubic perovskite (A2BB'O-6) structure with lattice constant a=8.430 A. The dielectric constant and loss factor of YBa2SnO5.5 are in a range suitable for its use as substrate for microwave applications. YBa2SnO5.5 is found to be chemically compatible with both YBCO and BiSCCO superconductors. The thin film of YBCO screen printed on polycrystalline YBa2SnO5.5 substrate gave a Tc(0) of 92 K and a critical current density (Jc) of 4x104 A/cm2 at 77K. A screen printed BiSCCO thick film on YBa2SnO5.5 substrate gave Tc(0)=110K and current density 3x103 A/cm2 at 77 K. (author). 9 refs., 5 figs., 1 tab

  4. Synthesis and refinement of ferroelectric ceramic BaBi4Ti4O15 (BBT) using Rietveld Methods

    International Nuclear Information System (INIS)

    The lead zirconate titanate (PZT) has potential application in nonvolatile ferroelectric memory and capacitors, however this material is linked to environmental pollution. In order to remedy this problem, we propose the synthesis of the compound, BaBi4TI4O15 (BBT) because of similarity to PZT. The phase of the BBT has been prepared by the method of solid state. Reagents (BaCO3, Bi2O3 and TiO2) were ground for 6 hours at 360 rpm in a planetary ball mill and suffered high energy heat treatment for 2 hours at temperatures of 850, 900, 950 and 1000 ° C. The calcined powder was characterized by X-ray diffraction (XRD) and refined by the program DBWSTools 2.3 Beta based on the Rietveld method. The results obtained confirmed the refinement of the single-phase with tetragonal structure BaBi4TI4O15 for all samples. The sample calcined at 950 °C presented the best densification (7.508 g/cm³). (author)

  5. 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.

  6. 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.

  7. 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. PMID:27362345

  8. 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.

  9. Structure, phase evolution, and microwave dielectric properties of (Ag0.5Bi0.5)(Mo0.5W0.5)O4 ceramic with ultralow sintering temperature.

    Science.gov (United States)

    Zhou, Di; Li, Wen-Bo; Guo, Jing; Pang, Li-Xia; Qi, Ze-Ming; Shao, Tao; Xie, Hui-Dong; Yue, Zhen-Xing; Yao, Xi

    2014-06-01

    In the present work, the microwave dielectric ceramic (Ag0.5Bi0.5)(Mo0.5W0.5)O4 was prepared by using the solid-state reaction method. (Ag0.5Bi0.5)(Mo0.5W0.5)O4 was found to crystallize in the scheelite structure, in which Ag(+) and Bi(3+) occupy the A site randomly with 8-coordination while Mo(6+) and W(6+) occupy the B site with 4-coordination, at a sintering temperature above 500 °C, with lattice parameters a = b = 5.29469(2) Å and c = 11.62114(0) Å, space group I4(1)/a (No. 88), and acceptable Rp = 9.38, Rwp = 11.2, and Rexp = 5.86. High-performance microwave dielectric properties, with permittivity ∼26.3, Qf value ∼10,000 GHz, and temperature coefficient ∼+20 ppm/°C, were obtained in the sample sintered at 580 °C. Its chemical compatibility with aluminum at its sintering temperature was revealed and confirmed by both X-ray and energy dispersive spectrometer analysis. This ceramic could be a good candidate for ultralow-temperature cofired ceramics. PMID:24848200

  10. Enhanced piezoelectricity in (1 -x)Bi1.05Fe1-yAyO3-xBaTiO3 lead-free ceramics: site engineering and wide phase boundary region.

    Science.gov (United States)

    Zheng, Ting; Jiang, Zhenggen; Wu, Jiagang

    2016-07-28

    Site engineering has been employed to modulate the piezoelectric activity of high temperature (1 -x)Bi1.05Fe1-yScyO3-xBaTiO3 lead-free ceramics fabricated by a conventional solid-state method together with a quenching technique. The effects of x and y content on the phase structure, microstructure, and electrical properties have been investigated in detail. A wide rhombohedral (R) to pseudo-cubic (C) phase boundary was formed in the ceramics with x = 0.30 and 0 ≤y≤ 0.07, thus leading to enhanced piezoelectricity (d33 = 120-180 pC N(-1)), ferroelectricity (Pr = 19-22 μC cm(-2)) and a high Curie temperature (TC = 478-520 °C). In addition, the influence of different element substitutions for Fe(3+) on phase structure and electrical behavior was also investigated. Improved piezoelectricity (d33 = 160-180 pC N(-1)) and saturated P-E loops can be simultaneously achieved in the ceramics with A = Sc, Ga, and Al due to the R-C phase boundary. As a result, site engineering may be an efficient way to modulate the piezoelectricity of BiFeO3-BaTiO3 lead-free ceramics. PMID:27357104

  11. The effect of CuO and NiO doping on dielectric and ferroelectric properties of Na0.5Bi0.5TiO3 lead-free ceramics

    Science.gov (United States)

    Kakroo, Sunanda; Kumar, Arvind; Mishra, S. K.; Singh, Vijay; Singh, Pramod K.

    2016-03-01

    In the present work, lead-free piezoelectric ceramics (Na0.5Bi0.5)TiO3 -xCuO-yNiO (for x = 0.0, 0.02, 0.04 and 0.06) have been prepared by a conventional solid-state reaction method. An investigation of CuO and NiO doping in bismuth sodium titanate (BNT) and a study of the structure, morphology, and dielectric and ferroelectric properties of the NBT-CuNi system have been conducted. Phase and microstructural analysis of the (Na0.5Bi0.5)TiO3 (NBT) based ceramics has been carried out using X-ray diffraction and scanning electron microscopy (SEM) techniques. Field emission scanning electron microscopy (FE-SEM) images showed that inhibition of grain growth takes place with increasing Cu and Ni concentration. The results indicate that the co-doping of NiO and CuO is effective in improving the dielectric and ferroelectric properties of NBT ceramics. Temperature-dependent dielectric studies have also been carried out at room temperature to 400 °C at different frequencies. The NBT ceramics co-doped with x = 0.06 and y = 0.06 exhibited an excellent dielectric constant ɛr = 1514. The study suggests that there is enormous scope of application of such materials in the future for actuators, ultrasonic transducers and high-frequency piezoelectric devices.

  12. The effect of aging on the superconducting transition temperature and resistivity of Y-Ba-Cu-O ceramics after high temperature treatment

    International Nuclear Information System (INIS)

    Some changes in superconducting transition temperature Tc and normal resistivity r of YBa2Cu30x ceramics are investigated as a result of the aging stimulated by high temperature treatment and slow cooling to room temperature followed by the storage under environmental conditions during 255 hours. It is shown that the changes of these parameters fall on three specific intervals of storage time ta. In addition, different types of aging processes: fast and slow ones are observed for the heat-treated samples. It is found that the fast processes are accompanied by a slight increase of r and Tc within the first interval of storage time ta (ta ≤ 162 hrs.), while the slow processes correlate with a sharp decrease of Tc and simultaneous increase of r within the second aging interval (162 hrs. ≤ ta ≤ 206 hrs.). It is revealed that the fast and slow aging processes result from the redistribution of atoms in intergranular weak and strong links, correspondingly. The probable reason of the observed results is the formation and coexistence of various structural phases including the semiconducing one

  13. 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.

  14. Performance enhancement of thin-film ceramic electrolyte fuel cell using bi-layered yttrium-doped barium zirconate

    International Nuclear Information System (INIS)

    A thin-film yttrium-doped barium zirconate comprised of two distinct layers with different porosity was fabricated by pulsed laser deposition method for a low-temperature solid oxide fuel cell electrolyte to enhance electrode reactions and suppress electric short-circuit problem simultaneously. At 250 °C, the peak power density of bi-layer electrolyte fuel cell was ∼ 2 mW/cm2, which is ∼ 56% higher than that of single-layer electrolyte fuel cell due to significant reduction of cathodic activation loss. A set of materials characterizations revealed that the differences in compositions and micro-structures at the electrolytes accounts for the improved performance. - Highlights: • Bi-layer thin-film electrolyte was fabricated with pulsed laser deposition method. • Electrochemical performance was investigated at 250 °C. • The porous layer at the cathode surface improved oxygen reduction reaction. • Compositional and structural properties were examined with ex situ characterizations

  15. 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.

  16. 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

  17. Conductance fluctuations in high temperature critical superconducting system based on Bi2Sr1.4(Pb)0.6Ca2-xYxCu3 O10+y. thick films

    International Nuclear Information System (INIS)

    Bi2(Sr1.4)Pb0.6Ca2−xYxCu3O10+y superconducting thick films were prepared and deposited on MgO (100) substrates using a Melt-Quench-Annealing method (MQA).The superconducting transition was found around 89 K. Electrical conductance fluctuations and the thermodynamic fluctuations, close to Tc, were analyzed from results of R vs T measurements on the samples. Ytrium concentration range was in the range 0 ≤ x ≤ 0.8. Additionally, considering the Aslamazov-Larkin law, with Tc value fixed according to d 2R/dT2 criterion, the conductance trend in the samples was revealed. So, when x ≤ 0.075 a 3D behavior was found, on the other hand when the concentration increases to x = 0.8 a 2D behavior is stabilized. From these characteristics a correlation to the structural properties of the sample can be inferred

  18. 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

  19. Investigation of response of high-temperature superconducting Bi2Sr2CaCu2Oy bolometer at hard substrate on infrared laser pulses of permanent power and variable relative pulse duration

    International Nuclear Information System (INIS)

    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 Bi2Sr2CaCu2Oy 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

  20. 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.

  1. 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.

  2. Influence of oxygen-partial pressure controlled sintering on physical properties of (Bi0.5Na0.5TiO3)0.94(BaTiO3)0.06 ceramics

    International Nuclear Information System (INIS)

    High-density (Bi0.5Na0.5TiO3)0.94(BaTiO3)0.06 (BNBT-6) ceramics were fabricated under varying oxygen partial pressure conditions to develop useful lead-free piezoelectric materials with high mechanical quality factors (Qm). Influence of oxygen partial pressure-controlled sintering on physical properties of BNBT-6 ceramics was investigated. A liquid phase occurred in the sample sintered under logP(O2) = - 3.50 atm because part of the Bi, a highly volatile element, evaporated from the sample surface during sintering. The mechanical quality factor, Qm, for the radial vibration mode exhibited a maximum (= 270) at logP(O2) = - 3.50 atm that was 1.4 times as large as that of the sample sintered at logP(O2) = - 0.12 atm. The temperature coefficients of resonant and antiresonant frequencies (TCFfr1 and TCFfa1) of the BNBT-6 sample sintered under logP(O2) = - 3.50 atm were almost constant: TCFfr1 = 465 ppm/ .deg. C for the fundamental resonant frequency and TCFfa1 = 381 ppm/ .deg. C for the fundamental antiresonant frequency. The current technology produces a substantial improvement in Qm characteristics without lowering other piezoelectric parameters, such as relative permittivity, εr, and electromechanical coupling factors, kp and kt, and can be expected to extend the selectivity of electrode materials used in multilayer ceramic actuators.

  3. Effect of La and Sr co-doping on electric and magnetic properties of multiferroic La0.1Bi0.9-xSrxFeO(3-x/2) ceramics

    Science.gov (United States)

    Guo, Feng; Wang, Shouyu; Liu, Weifang; Wang, Xu; Liu, Li; Li, Meng

    2015-09-01

    La0.1Bi0.9-xSrxFeO(3-x/2)(LBFSx0 ≤ x ≤ 0.8) ceramics were synthesized by solid-state reaction method, and their magnetic properties and conductive characteristics were investigated and discussed. It is found that La-doped BiFeO3 ceramic without Sr2+ doping is a rhombohedrally distorted perovskite structure, and with the increase of the Sr2+ concentration, the phase transits gradually from rhombohedral to pseudo cubic symmetry. Electrical and magnetic properties show strong dependence on Sr2+ dopant level. The measurement demonstrates that LBFSx with 30% Sr2+ dopant exhibits the lowest values of the leakage current, dielectric constant (ɛ) and dielectric loss (tan δ). And the highest value of saturation magnetization of about 4.5 emu/g is observed in 60% Sr-doped LBFSx. An abnormal enhancement of the conductivity was observed in LBFSx ceramics with x = 0.60 and 0.70, and their magnitude of conductivity is nearly six orders larger than that of pure LBFSx.

  4. Ceramic synthesis of 0.08BiGaO3-0.90BaTiO3-0.02LiNbO3 under high pressure and high temperature

    Institute of Scientific and Technical Information of China (English)

    金慧; 李勇; 宋谋胜; 陈琳; 贾晓鹏; 马红安

    2016-01-01

    In this paper, the preparation of 0.08BiGaO3-0.90BaTiO3-0.02LiNbO3 is investigated at pressure 3.8 GPa and tem-perature 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 morphol-ogy 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.

  5. 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)

  6. 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.

  7. 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.

  8. Bi2O3和Al2O3共掺杂对BaTiO3陶瓷介电弛豫性能的影响%Effect of co-doping of Bi2 O3 and Al2 O3 on the dielectric relaxation properties of BaTiO3 ceramics

    Institute of Scientific and Technical Information of China (English)

    蒲永平; 王亚茹; 郭一松; 郑晗煜; 靳乾; 姚谋腾; 吴思辰

    2015-01-01

    The co‐doping of Bi2 O3 and Al2 O3 into BaTiO3 ceramics have been prepared through solid state reaction route .The dielectric relaxation properties of BT + 0 .5 mol%Bi2 O3 + x mol% Al2 O3 (x=0 .00 ,0 .25 ,0 .75 ,1 .00 ,2 .00 ,3 .00)ceramics have been researched by using the testing means of dielectric temperature characteristics and ferroelectric hystere‐sis loop .The results showed that the dielectric constant of ceramic decreases with the in‐creasing value of x .T he relaxation behavior of the ceramics can be proved by the values of Tm ,Trelax and Tdif according to the Curie Weiss law .The value of Tm、Tc、Tcw 、ΔTm、εm、γ、ΔTdif and ΔTrelax proved that relaxation behavior was the most obvious when x=3 .00 .The dielectric relaxation of BT+0 .5 mol% Bi2 O3 +3 mol% Al2 O3 follow s the Vogel‐Fulcher rela‐tionship with Ea=0 .067 8 eV ,Tf =382 .28 K ,and f0 =1 .76 × 1018 Hz ,furthermore ,the dif‐fuse frequency transition of ceramic is in accordance with spin‐glass‐like characteristics , w hich proves the relaxation behavior of ceramic is similar to spin‐glass .%采用固相法制备了Bi2 O3和Al2 O3共掺杂的BaTiO3(BT )陶瓷.通过介电温度特性、电滞回线测试手段研究了BT+0.5 mol% Bi2 O3+ x mol% Al2 O3(x=0.00,0.25,0.75,1.00, 2.00,3.00)陶瓷的介电弛豫性能.研究结果发现:随着 x的增大,陶瓷介电常数逐渐降低.根据居里外斯定律得到 Tm ,Trelax 和 Tdif (1 kHz)值,证明了BT +0.5 mol% Bi2 O3+ x mol%Al2 O3的弛豫行为.Tm、Tc、Tcw 、ΔT m、εm、γ、ΔT dif 和ΔT relax 值得到x =3.00陶瓷样品的弛豫现象最明显,根据Vogel‐Fulcher方程,BT+0.5 mol% Bi2 O3+3 mol% Al2 O3陶瓷物理特征参数 Ea为0.0678 eV ,Tf 为382.28 K ,f0为1.76×1018 Hz ,并且实验所得数据与Vogel‐Fulcher拟合曲线相符,陶瓷样品出现频率色散的过程符合玻璃态模型,类

  9. 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).

  10. A study of the heat treatment time, temperature and ramp rate on the transport current properties and Bi-2223 grain growth in (Bi,Pb)2223/Ag superconducting tapes

    CERN Document Server

    Young, E A

    2002-01-01

    The Bi-2223 phase formation in (Bi,Pb)2223/Ag tapes is known to be via a Pb rich liquid phase, the control of the wetting properties and the phase volume of liquid phase in the early hours of sintering can substantially improve the transport current of the final sintered tape. The phase volume of liquid phase, characterised by the formation of the Bi sub 2 (Sr sub 1 sub . sub 6 Ca sub 0 sub . sub 4)CuO sub 6 , (Bi-2201), phase, was observed to depend on the heat treatment temperature and atmosphere. The volume of secondary phases, (Cu sub 2 O, Cu-free phase, and Bi sub 2 (Sr sub 1 sub . sub 6 Ca sub 0 sub . sub 4)CuO sub 6), in the sintered Bi-2223 microstructure is shown to be sensitive to the sintering heating rate, and this is thought to be related to the wetting properties of the liquid phase. For an optimum transport critical current, (77K, self field), the heat treatment temperature and the heating rate are inter-dependent parameters, the heating rate only increasing the transport current of tapes heat ...

  11. 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.

  12. 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.

  13. Structures, phase transformations, and dielectric properties of (1-x)Bi2Zn2/3Nb4/3O7-xBi1.5NiNb1.5O7 pyrochlore ceramics prepared by aqueous sol-gel method

    International Nuclear Information System (INIS)

    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 τε together with a high εr 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)Bi2Zn2/3Nb4/3O7-xBi1.5NiNb1.5O7 (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 Bi1.5NiNb1.5O7 content. The phase stability of the orthorhombic and cubic pyrochlore phase in the (1-x)β-BZN-xBNN system was dependent on the Bi3+ content as well as the distribution and variety of divalent cations, such as Ni2+/Zn2+ 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 (τε) was obtained and the dielectric constant (εr) 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 (τε≤± 30 ppm/°C between -55 and 125 °C) exhibited excellent dielectric properties of εr = 105.6, small dielectric tangent (tan δ) ∼ 10-4, τε = -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

  14. 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.

  15. Enhanced energy storage performance of glass added 0.715Bi0.5Na0.5TiO3-0.065BaTiO3-0.22SrTiO3 ferroelectric ceramics

    Directory of Open Access Journals (Sweden)

    Satyanarayan Patel

    2015-12-01

    Full Text Available In the present work, lead-free ferroelectric 0.715Bi0.5Na0.5TiO3-0.065BaTiO3-0.22SrTiO3 (BNT-BT-ST bulk ceramics with 3BaO-3TiO2-B2O3 (BTBO glass additive were fabricated by conventional solid state reaction route. The effect of glass content on microstructure and energy storage properties of BNT-BT-ST ceramics was investigated. The maximum energy storage of ∼203 kJ/m3 was achieved for BNT-BT-ST ceramic with addition of 4 wt.% glass. The 4 wt.% glass addition improves energy storage density and energy storage efficiency by ∼15% and ∼52% higher than that of the pure BNT-BT-ST, respectively. The effect of temperature on the energy storage was also estimated. It was observed the temperature has similar effect on energy storage improvement in all compositions. The energy storage density (U dependent scaling behavior on remnant polarization (Pr, maximum polarization (Pmax, electric field (E and temperature (T was also studied. The results of this study are expected to largely benefit the field of ferroelectric based capacitors in discerning the dependency of U on hysteresis parameters (Pr, Pmax, and E and T.

  16. 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.

  17. The structural and multiferroic properties of (Bi{sub 1-x}La{sub x})(Fe{sub 0.95}Co{sub 0.05})O{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Xu Qingyu, E-mail: xuqingyu@seu.edu.cn [Department of Physics, Southeast University, Nanjing, Jiangsu 211189 (China); Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing 210096 (China); Zheng Xiaohong [Department of Physics, Southeast University, Nanjing, Jiangsu 211189 (China); Wang Liaoyu [Department of Physics, Nanjing University, Nanjing 210008 (China); Zhang Yan [Department of Physics, Southeast University, Nanjing, Jiangsu 211189 (China); Wang Dunhui [Department of Physics, Nanjing University, Nanjing 210008 (China); Xu Mingxiang [Department of Physics, Southeast University, Nanjing, Jiangsu 211189 (China)

    2012-12-15

    La and Co co-doped BiFeO{sub 3} ((Bi{sub 1-x}La{sub x})(Fe{sub 0.95}Co{sub 0.05})O{sub 3} (x=0, 0.10, 0.20, 0.30)) ceramics were prepared by tartaric acid modified sol-gel method. The X-ray diffraction patterns indicate a transition from rhombohedral structure to tetragonal structure at x=0.20, which has been confirmed by the Raman measurements. The band gap increases with increasing x to 0.20, and then decreases with further increasing x to 0.30. The structural transition has significant effects on the multiferroic properties. The remnant magnetization and saturate ferromagnetic magnetization decrease abruptly with increasing x to 0.10, and then gradually increase with further increasing x up to 0.30. The coercivity is significantly reduced with increasing La doping concentration. The ferroelectricity has been improved by La doping, and the polarization increases with increasing x to 0.10, then decreases with further increasing x up to 0.30. The simultaneous coexistence of soft ferromagnetism and ferroelectricity at room temperature in tetragonal Bi{sub 0.70}La{sub 0.30}Fe{sub 0.95}Co{sub 0.05}O{sub 3} indicates the potential multiferroic applications.

  18. 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.

  19. ANL-1(A) - Development of nondestructive evaluation methods for structural ceramics

    International Nuclear Information System (INIS)

    This section includes the following papers: Development of Nondestructive Evaluation Methods for Structural Ceramics; Effects of Flaws on the Fracture Behavior of Structural Ceramics; Design, Fabrication, and Interface Characterization of Ceramic Fiber-Ceramic Matrix Composites; Development of Advanced Fiber-Reinforced Ceramics; Modeling of Fibrous Preforms for CVD Infiltration; NDT of Advanced Ceramic Composite Materials; Joining of Silicon Carbide Reinforced Ceramics; Superconducting Film Fabrication Research; Short Fiber Reinforced Structural Ceramics; Structural Reliability and Damage Tolerance of Ceramic Composites for High-Temperature Applications; Fabrication of Ceramic Fiber-Ceramic Matrix Composites by Chemical Vapor Infiltration; Characterization of Fiber-CVD Matrix interfacial Bonds; Microwave Sintering of Superconducting Ceramics; Improved Ceramic Composites Through Controlled Fiber-Matrix Interactions; Evaluation of Candidate Materials for Solid Oxide Fuel Cells; Ceramic Catalyst Materials: Hydrous Metal Oxide Ion-Exchange Supports for Coal Liquefaction; and Investigation of Properties and Performance of Ceramic Composite Components

  20. 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.

  1. 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.

  2. Microscopic fracture of filaments and its relation to the critical current under bending deformation in (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} composite superconducting tapes

    Energy Technology Data Exchange (ETDEWEB)

    Hojo, Masaki [Department of Mechanical Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan); Nakamura, Mitsuhiro [Department of Mechanical Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan); Matsuoka, Tomoe [Department of Mechanical Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan); Tanaka, Mototsugu [Department of Mechanical Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan); Ochiai, Shojiro [International Innovation Center, Kyoto University, Kyoto 606-8501 (Japan); Sugano, Michinaka [National Institute for Materials Science, Tsukuba 305-0003 (Japan); Osamura, Kozo [Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501 (Japan)

    2003-09-01

    The strain dependence of the critical current, I{sub c}, of (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} (Bi2223)/Ag/Ag-Mg composite superconducting tapes has been studied both experimentally and analytically under bending deformation. Tests have been carried out for one type of tape used in the VAMAS bending round-robin programme. The complex stress-strain behaviour of each component was first analysed in tension. This was done by comparing the stress-strain curves of composite tapes with those of Ag and Ag-Mg alloy tapes. Here, the plastic deformation (work hardening) of Ag and Ag-Mg alloy, and the thermal residual strain due to the manufacturing process were taken into account. The fracture strain of Bi2223 filaments was inversely determined as 0.08% to meet the global tensile stress-strain curve of the composite tape. The calculated stress-strain curves finally agreed well with the experimental results when the as-supplied bending strain was taken into account. Then, the analysis was modified to fit the bending deformation. Here, the movement of the neutral axis due to the non-symmetric and elastic-plastic stress-strain curves of the components and their Bauschinger effect were taken into account. The relative decrease of I{sub c} with the increase in the Bi2223 tape curvature was calculated from the volume fraction of the broken filaments. The calculated I{sub c} agreed well with the experimental results when the movement of the neutral axis and the Bauschinger effect were taken into account. Microscopic observation of the spatial distribution of the filament fracture indicated that the damage occurred at the outermost layer on the tensile side when the curvature was small, and then the damage front shifted to the inside layers. The observed fracture behaviour of the Bi2223 filament agreed well with the estimated location based on the above analysis.

  3. 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.

  4. 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.).

  5. 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

  6. Oxygen octahedra distortion induced structural and magnetic phase transitions in Bi1-xCaxFe1-xMnxO3 ceramics

    Science.gov (United States)

    Kumar, Pawan; Shankhwar, Nisha; Srinivasan, A.; Kar, Manoranjan

    2015-05-01

    The co-doping of Ca and Mn in respective Bi and Fe-sites of BiFeO3 lattice leads to structural transition from rhombohedral (R3c space group) to orthorhombic (Pbnm space group) crystal symmetry. The tilt angle for anti-phase rotation of the oxygen octahedra of BiFeO3 at room temperature is observed to be ˜13.8°. It decreases with the increase in the co-doping percentage which suggests the composition-driven structural phase transition. The remnant magnetization for sample with 15% of co-doping becomes about 16 times that of BiFeO3. It may be attributed to the suppression of cycloid spin structure and uncompensated spins at the surface of nanocrystallites. Further increase in co-doping percentage results in the sharp reduction of remnant magnetization due to the dominant contribution from the collinear antiferromagnetic ordering in the Pbnm space group. The Arrott plot analysis clearly indicates the composition-driven crossover from the antiferromagnetic to weak ferromagnetic ordering and vice versa. Electron spin resonance results provide the evidence for the composition-driven phase transitions from an incommensurate spin cycloidal modulated state to one with nearly homogeneous spin order. The band gap (2.17 eV) of BiFeO3 measured using UV-Vis spectra was supported by the resonance Raman spectra.

  7. 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.

  8. 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.

  9. 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.

  10. Development and preparation of superconducting mixed oxides by means of the reaction spray technique. Final report

    International Nuclear Information System (INIS)

    The report summarizes the work leading to a modification of the reaction spray technique in order to apply this technique for the preparation of powders for ceramic high-Tc superconductors. The task was to modify an existing reaction spray equipment to the specific requirements of the intended system for powder preparation and subsequent fabrication of superconducting, sintered specimens. The modification of the existing reaction spray equipment was relatively soon completed, and further optimizations finally resulted in a system capable of processing the material (YBaCuO; BiSrCaCuO) in batches of 10 kg in a routine operation mode, which proved to be a successful achievement for the fabrication of the sintered parts, which were formed by axial pressing and isostatic or hot pressing, or by thin film techniques. All the techniques were designed so as to yield superconducting specimens suitable for fabricating superconducting component parts. The Tc-values achieved were approx. 92 K (110 K) for YBaCuO (BiSrCaCuO). The jc values achieved 102 .. 103 A/cm2, represent the currently best achievable results for polycrystalline, sintered materials without any further structural optimization treatment being done. The dimensions of the disks, hollow cylinders, and thin films cover a range from several centimeters up to decimeters. (orig.)

  11. 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.

  12. 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.

  13. Quantum oscillations in strong magnetic fields, berry phase, and superconductivity in three-dimensional topological Bi{sub 2–x}Cu{sub x}Se{sub 3} insulators

    Energy Technology Data Exchange (ETDEWEB)

    Vedeneev, S. I., E-mail: vedeneev@sci.lebedev.ru; Knyazev, D. A.; Prudkoglyad, V. A.; Romanova, T. A.; Sadakov, A. V. [Russian Academy of Sciences (Russian Federation)

    2015-07-15

    Two-dimensional (2D) Shubnikov–de Haas oscillations and 2D Hall oscillations are observed in 3D copper-doped Bi{sub 2}Se{sub 3} single crystals in magnetic fields up to 19.5 T at temperatures down to 0.3 K. Three samples with a high bulk carrier concentration (n ≈ 10{sup 19}–10{sup 20} cm{sup –3}) are studied. The rotation of the samples in a magnetic field shows that these oscillations are related to numerous parallel 2D conducting channels 1–5 nm thick. Their basic kinetic parameters are found. Quantized Hall resistance R{sub xy} is detected in 1-nm-thick 2D conducting channels at high fields. The distance Δ(1/R{sub xy}) between the steps in the field dependence of 1/R{sub xy} is found to be constant for different Landau levels, 1.3e{sup 2}/h per 1-nm-thick layer. The constructed fan diagrams of 2D Landau levels for various angles of sample inclination with respect to the magnetic field direction allowed us to conclude that the Berry phase in the 2D conducting channels is γ ≈ π and independent of the magnetic field direction. When studying the angular dependence of upper resistive critical magnetic field H{sub c2} in one of the superconducting samples, we showed that it can be considered as a bulk superconductor consisting of superconducting layers with an effective thickness of about 50 nm.

  14. Microstructures and critical current densities of melt-processed Bi2Sr2CaCu2Ox superconductor

    International Nuclear Information System (INIS)

    The best method to prepare high-temperature superconducting devices of Bi2Sr2CaCu2Ox (Bi-2212), able to carry large transport currents at 77 K is the partial melt-processing. During this heat-treatment the cuprate is melted and subsequently crystallized upon controlled cooling. Almost all involved processing parameters have to be controlled within narrow limits in order to get good superconducting properties in the fully processed sample. This work investigates the influence of the processing conditions on the microstructure and the superconducting properties of Bi-2212 thick films and bulk components covering the thickness range from 10 to 1000 μm. The melting behavior of Bi-2212 in various atmospheres and with silver additions (0 to 16 wt%) is described. Thick films were submitted to an optimized partial melt-processing and the microstructural evolution from the porous green-body to the dense and aligned microstructure in the fully processed samples was studied. The influence of processing parameters on the microstructure and the superconducting properties of fully processed thick films and bulk components was examined. The melting behavior of Bi-2212 is strongly determined by the oxygen partial pressure of the surrounding atmosphere and the silver content of the ceramic powder. The solidus temperature of the pure Bi-2212 powder is decreased from 893oC in oxygen (pO2=1 atm) to 834oC if melted at pO2=0.001 atm. The addition of silver to Bi-2212 further decreases Tsolidus by up to 25 K if melted in oxygen. During thermal decomposition, Bi-2212 releases oxygen into the atmosphere, resulting in a weight loss of the sample. The oxygen loss is strongest at low oxygen partial pressures of the atmosphere and is reduced from 1.6 wt% at pO2=0.001 atm to 1.1 wt% in pure oxygen atmosphere. The extra addition of silver further reduces the oxygen loss upon melting by increasing the oxygen solubility of the melt. The corrosion of the silver substrate is reduced because less

  15. 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)

  16. 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.

  17. 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.

  18. Preparation and characterization of silver clad (Bi,Pb)-Sr-Ca-Cu-O 2223 superconducting tapes with high critical current density

    International Nuclear Information System (INIS)

    Silver clad Bi-2223 tapes with consistently high critical current densities of over 30,000 A/cm2 at 77 K and zero field were prepared by powder-in-tube (PIT) technique. Powder XRD, electron microscopy, a.c. susceptibility and critical current measurements were used to study the phase assemblage, microstructure and transport properties of these tapes at various stages of processing. The precursor powder for PIT process was prepared by a sol-gel route by acrylate method using freshly prepared nitrates of Bi, Pb, Sr, Ca and Cu. The carbon content in the powder was minimized by subjecting it under dynamic vacuum calcination followed by heating in free flow of oxygen for long durations with intermittent grindings. The choice of initial stoichiometry, high reactivity of the precursor, effective removal of carbon, choice of phase assemblage at the filling stage and the multistage thermomechanical processing at optimized conditions were found to be responsible for the high critical current density. (author). 16 refs., 6 figs., 2 tabs

  19. Superconductivity and magnetism in niobium doped YBa{sub 2}Cu{sub 3}O{sub 7} related high-{Tc} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Bennahmias, M. [Lawrence Livermore National Lab., CA (United States)]|[California Univ., Livermore, CA (United States). Dept. of Applied Science; Radousky, H.B. [Lawrence Livermore National Lab., CA (United States)]|[California Univ., Davis, CA (United States). Dept. of Physics; Goodwin, T.J.; Shelton, R.N. [California Univ., Davis, CA (United States). Dept. of Physics

    1993-02-01

    Magnetic characterization has been performed on the members of the cuprate-niobate RBa{sub 2}Cu{sub 2}NbO{sub 8} (R = Pr, Nd, and La) series and R{sub l.5}Ce{sub 0.5}Sr{sub 2}Cu{sub 2}NbO{sub 10} (R = Pr, Eu, Nd, and Sm) series. The PrBCNO samples show a signature in the magnetization of a magnetic ordering at 12 K. The PrCSCNO sample is non-superconducting and shows two distinct orderings at 17 and 53 K. No such magnetic phase transition is observed down to 2 K in the Nd and La based RBCNO materials or the Nd, Sm, and Eu based RCSCNO materials. Measurements of the lower critical field curve, dc irreversibility line, and critical current densities are reported for each of the superconducting NdCSCNO, SmCSCNO, and EuCSCNO compounds.

  20. Manipulating superconducting films with magnetic nanostripes

    International Nuclear Information System (INIS)

    Highlights: • Magnetic nanostripes strongly pin vortices in PbBi-Ni hybrids. • Magnetic nanostripes are ineffective in pinning vortices in Sn-Co hybrids. • Effective magnetic pinning by magnetic nanostripes requires coherence length significantly smaller than nanostripe period. -- Abstract: We present studies of the transport properties of a Pb82Bi18 and Sn superconducting film with an array of parallel nickel or cobalt magnetic nanostripes (500 nm period) deposited on the top of a germanium insulating layer covering the superconducting film surface. The critical current parallel to the stripes is significantly larger than critical current perpendicular to the stripes for Pb82Bi18

  1. Study and characterization of the BBT (BaBi{sub 4}Ti{sub 4}O{sub 15}) ceramic added with 1 wt. % Nb{sub 2}O{sub 5}; Estudo e caracterizacao da ceramica BBT (BaBi{sub 4}Ti{sub 4}O{sub 15}) dopada com 1% de Nb{sub 2}O{sub 5}

    Energy Technology Data Exchange (ETDEWEB)

    Silva, P.M.O.; Sales, A.J.M.; Freitas, D.B.; Oliveira, R.G.M.; Sombra, A.S.B., E-mail: paulo2003@gmail.com [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil); Sales, J.C. [Universidade Estadual Vale do Acarau (UVA), Fortaleza, CE (Brazil)

    2012-07-01

    This study aims to synthesize and characterize the ceramic BBT (BaBi{sub 4}TI{sub 4}O{sub 15}) doped with 1% by mass of the densification Nb2O5 to improve the products. The phase of the BBT has been found by solid state reaction. The mixed oxides starting processed by high-energy milling in planetary mill reactor polymer and spheres of zirconia and calcined at 850°C/3h. Later, 'bulks' prepared with the calcined powder were sintered at 950°C/3h. The calcined powder was characterized by X-ray diffraction data and refined by the beta 3.2 DBWSTools program using the Rietveld method. The grain morphology and distribution of pores on the surface of the 'bulks' were analyzed by Scanning Electron Microscopy. The result confirmed the refined to obtain the single phase with tetragonal structure BaBi{sub 4}TI{sub 4}O{sub 15} density of 5.088 g/cm3 calculated in the unit cell. SEM analysis by SEM showed improved densification of the doped. (author)

  2. Study of structural and electrical properties of ceramics SrBi{sub 2}Nb{sub 2}O{sub 9} manufactured by high energy milling; Estudo de propriedades estruturais e eletricas da ceramica SrBi{sub 2}Nb{sub 2}O{sub 9} fabricada por moagem de alta energia

    Energy Technology Data Exchange (ETDEWEB)

    Sancho, E.O., E-mail: emmanuellesancho@hotmail.com [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil). Departamento de Engenharia Metalurgica e de Materiais; Freitas, D.B.; Silva Filho, J.M.; Sombra, A.S.B. [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil). Dept. de Fisica. Lab. de Telecomunicacoes e Ciencia e Engenharia de Materiais; Sales, J.C. [Universidade Estadual Vale do Acarau, Acarau, CE (Brazil). Centro de Ciencias Exatas e Tecnologicas. Departamento de Engenharia

    2012-07-01

    Was synthesized compounds of bismuth, SrBi{sub 2}Nb{sub 2}O{sub 9} (SBN) by the method of solid state by high energy milling reactor polymeric beads zirconia, and to it were added to concentrations of 3, 5, 10 and 15% bismuth oxide (Bi{sub 2}O{sub 3}) in order to promote intentional changes in the chemical structure of the ceramic. In this work we studied the structural and electrical properties (in the region of 10Hz to 100MHz). Was obtained diffractograms showing the formation of phase, and by Rietveld refinement confirmed the orthorhombic crystal structure with lattice parameter (a = 5.5129Å, b = 5.5183Å and c = 25.0819Å, α = β = γ = 90 deg) convergence rates for S = 1.59 (goodness of fit), where S is given by the ratio Rwp/Rexp. The dielectric permittivity and dielectric loss were directly related to the porosity using density measurements obtained. (author)

  3. Study of vortex dynamics with local magnetic relaxation measurements in the superconducting compound Bi2Sr2CaCu2O8

    International Nuclear Information System (INIS)

    This experimental study of the magnetic field-temperature phase diagram and of the vortex dynamics in high- Tc superconductors focuses on Bismuth-based cuprates: Bi2Sr2CaCu2O8. 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. Bi2Sr2CaCu2O8 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)

  4. 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.

  5. Advanced ceramics: the present and the perspectives

    International Nuclear Information System (INIS)

    Development in the Brazilian and international areas of advanced ceramics is described, emphasizing its economic perspectivas and industrial applications. Results obtained by national institutions are reviewed, mainly in the context of those that pioneered the required high technology in this ceramic field. The rapid growth of the interest for those special materials, made more evident by ample information related to the superconducting ceramics great pontential for important practical applications, is one of the most significant characteristics of the area. (author)

  6. High temperature reactions, densification and the peritectic decomposition of YBa2-xSrxCu3O7-δ (YBSCO) superconducting ceramics

    International Nuclear Information System (INIS)

    For YBSCO ceramics (YBa2-xSrxCu3O7-δ with x=0, 0.2, and 0.4) solid state reactions, liquid phase formation and densification behavior up to the peritectic temperature (Tp) are characterized by differential thermal analysis (DTA) and dilatometer runs at controlled heating rates. There is an increase in the Tp from DTA when x is increased. Incremental growth in densification is detected at T∼950-975 deg. C which is assigned to the formation of a liquid phase as indicated by the endothermic peak in the DTA run. For T≥Tp the thickness of the pellets (measured continuously with the dilatometer) continued to decrease owing to the peritectic melting of the main (1 2 3) or (1 2 3)Sr (orthorhombic/tetragonal phase doped with Sr) phases. After an initial viscous flow decrease in height (time exponent close to one), the systems continued to densify with a time law approaching either t1/3 or t1/2. Such isothermal time behaviours are associated to the coarsening stage of the (2 1 1) crystals precipitated in the peritectic liquid. Peritectic decomposition for Sr containing ceramics was significantly slower than that for the undoped ceramics at roughly similar temperatures. The latter can be related to a lower diffusivity/solubility of Y in the doped peritectic liquid. From calibrated X-ray diffractometry it was found the (2 1 1) phase was definitely doped with Sr, meaning also the peritectic liquid could contain some levels of strontium

  7. 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.

  8. 高温超导SMES磁体直接冷却的热分析%THERMAL ANALYSIS ON CRYOCOOLER-COOLED BI-2223 SUPERCONDUCTING MAGNET

    Institute of Scientific and Technical Information of China (English)

    王建; 王惠龄; 石零; 唐跃进; 汪京荣; 冯勇

    2004-01-01

    用G-M制冷机(5W/20K)将Bi2223带材绕制的SMES超导磁体,在10-3Pa真空度下,从常温300K左右冷却到25K,得到了磁体冷却过程速率和磁体温度分布.在实验研究超导磁体降温特性的基础上,对SMES磁体的冷却过程进行了热分析,实验研究表明为使超导磁体有效地冷却和稳定运行,除了减小磁体漏热和其内部发热,有效控制热传导部件间的接触界面热阻是高温超导直接冷却磁储能装置研发应用中的关键技术问题.

  9. 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.

  10. Superconducting YBCO and YBCO-Ag thick films (Tc(0)=92 K) by dip coating on GdBa2HfO5.5, a new perovskite ceramic substrate

    International Nuclear Information System (INIS)

    A new ceramic perovskite, GdBa2HfO5.5, has been synthesized and developed for use as substrate for the YBa2Cu3O7-δ superconductor. The dielectric constant and loss factor of this material are in a range suitable for its use as substrate for microwave applications. No detectable chemical reaction between YBa2Cu3O7-δ and GdBa2HfO5.5 was observed even under severe heat treatment. YBa2Cu2O7-δ and YBa2Cu3O7-δ-Ag thick films dip coated on GdBa2HfO5.5 substrate gave a zero-resistivity superconducting transition of 92 K. The critical current density (Jc) of YBa2Cu3O7-δ thick film was 3*103 A cm-2 whereas a current density of 2*104 A cm-2 was obtained for YBa2Cu3O7-δ-Ag thick film. The YBa2Cu3O7-δ-Ag thick film showed preferred (001) orientation on polycrystalline GdBa2HfO5.5 substrate. (author)

  11. 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.

  12. 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…

  13. 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.

  14. 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.

  15. 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.

  16. 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.).

  17. 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.

  18. 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.

  19. 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)

  20. Development of a theoretical model for polycrystalline superconducting anisotropic using the effective medium approximation

    International Nuclear Information System (INIS)

    Full text: In this paper, is a study of the transport properties in anisotropic polycrystalline superconducting. The presence of certain order of orientation of grains in polycrystalline superconducting (Bi,Pb)2 Sr2 Ca2 Cu3 O10+delta, is modeled by introducing a probability of orientation, gamma factor. In addition, is included in the model the concentration c, which characterize the contribution of porosity to the decrease in the conductivity of the Crystal, transparent. Assumes that pores and pimples are ellipsoid flattened with similar dimensions and takes into account the values of conductivity of beads in each direction. The calculation is based on the application of a generalization of the approximation of the effective way to the study of heterogeneous media, which is called coherent potential approximation (APC). The results are compared with an empirical model developed recently for samples of YBa2 Cu3 O7-delta (YBCO) which enriches its employment and applied to ceramic superconducting in general. (author)

  1. 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.

  2. 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)

  3. 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.

  4. Effect of SrZrO{sub 3} substitution on structural and electrical properties of lead-free Bi{sub 0.5}Na{sub 0.5}TiO{sub 3}-BaTiO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Maqbool, Adnan; Hussain, Ali; Rahman, Jamil Ur; Park, Jong Kyu; Park, Tae Gone; Kim, Myong Ho [Engineering Research Center for Integrated Mechatronics Materials and Components, Changwon National University, Gyeongnam (Korea, Republic of); Song, Jae Sung [Korea Electrotechnology Research Institute, Gyeongnam (Korea, Republic of)

    2014-08-15

    In this study, a new lead-free ceramic system of (1-x)Bi{sub 0.5}Na{sub 0.5}TiO{sub 3}-0.065BaTiO{sub 3}-xSrZrO{sub 3} BNBT-SZ100x (with x = 0-0.10) was prepared by a conventional solid-state reaction method and its structural and electrical properties were studied. XRD analysis revealed the formation of pure perovskite phase for all ceramics. The temperature dependence of the dielectric curves showed that the maximum dielectric constant temperature (T{sub m}) shifted towards lower temperatures and the curves become more diffuse with increasing amount of SZ addition. The ferroelectric curves indicated a disruption of ferroelectric order upon SZ addition into BNBT ceramics. A maximum value of remnant polarization (30 μC cm{sup -2}), piezoelectric constant (197 pC N{sup -1}) and electromechanical coupling coefficient (29.4%) was observed for SZ1 ceramics. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. 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.

  6. 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)

  7. Advanced Ceramics

    International Nuclear Information System (INIS)

    The First Florida-Brazil Seminar on Materials and the Second State Meeting about new materials in Rio de Janeiro State show the specific technical contribution in advanced ceramic sector. The others main topics discussed for the development of the country are the advanced ceramic programs the market, the national technic-scientific capacitation, the advanced ceramic patents, etc. (C.G.C.)

  8. Superconducting linac

    International Nuclear Information System (INIS)

    This project has two goals: to design, build, and test a small superconducting linac to serve as an energy booster for heavy ions from an FN tandem electrostatic accelerator, and to investigate various aspects of superconducting rf technology. The main design features of the booster are described, a status report on various components (resonators, rf control system, linac control system, cryostats, buncher) is given, and plans for the near future are outlined. Investigations of superconducting-linac technology concern studies on materials and fabrication techniques, resonator diagnostic techniques, rf-phase control, beam dynamics computer programs, asymmetry in accelerating field, and surface-treatment techniques. The overall layout of the to-be-proposed ATLAS, the Argonne Tandem-Linac Accelerator System, is shown; the ATLAS would use superconducting technology to produce beams of 5 to 25 MeV/A. 6 figures

  9. Enhancement of Tc in BiS2-based superconductors NdO0.7F0.3BiS2 by substitution of Pb for Bi

    Science.gov (United States)

    Demura, S.; Fujisawa, Y.; Otsuki, S.; Ishio, R.; Takano, Y.; Sakata, H.

    2015-12-01

    We succeed in enhancement of a superconducting transition temperature (Tc) for NdO0.7F0.3BiS2 single crystal by partial substitution of Pb for Bi. The Tc increases with increasing Pb concentration until 6%. The maximum Tczero is 5.6 K, which is the highest value among BiS2-based based superconductors synthesized under an ambient pressure. Pb substitution for Bi induces lattice shrinkage along the c-axis. These results reflect that superconductivity in this system is responsive to the lattice strain.

  10. 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)

  11. 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.

  12. Growth of high T{sub c} superconducting fibers using a miniaturized laser-heated float zone process. Final technical report, January 15, 1989--December 31, 1994

    Energy Technology Data Exchange (ETDEWEB)

    Feigelson, R.S.; Route, R.K.; DeMattei, R.C.

    1995-04-01

    This report summarizes a four year program on the use of the laser-heated pedestral growth (LHPG) process for the preparation of long, flexible fibers of the high T{sub c} copper-oxide ceramic superconductors having wire-like morphology. The major question addressed was whether the LHPG method could produce high T{sub c} fibers of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} (2212) in lengths long enough for use as superconducting wires. Cold-pressing and sintering methods were developed to prepare uniform, single phase ceramic feedstock. Phase equilibrium studies revealed the relationship between thermal gradients, interface shape and phases produced by the LHPG process during incongruent solidification. The highest critical current densities over measured in bulk samples of Bi-2212 material, 60,000 A/cm{sup 2} at 68K, were achieved in single crystal and/or highly grain-oriented fibers. The first ever flexible, multi-cm fibers ({le}100 {mu}m in diameter) were prepared. Fibers diameters were ultimately reduced to 25 {mu}m (1 cm in length), and we were able to grow them up to 14 cm in length (100 {mu}m diameter). These fibers could be bent in radii less than 5 cm, but max. growth rates of {approximately}10 mm/hr did not permit them to be grown long enough for prototype motor windings. Superconducting Bi-2212 grain-aligned ribbons were grown for the first time by the LHPG method using platinum guide wires.

  13. Superconducting energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Giese, R.F.

    1993-10-01

    This report describes the status of energy storage involving superconductors and assesses what impact the recently discovered ceramic superconductors may have on the design of these devices. Our description is intended for R&D managers in government, electric utilities, firms, and national laboratories who wish an overview of what has been done and what remains to be done. It is assumed that the reader is acquainted with superconductivity, but not an expert on the topics discussed here. Indeed, it is the author`s aim to enable the reader to better understand the experts who may ask for the reader`s attention, support, or funding. This report may also inform scientists and engineers who, though expert in related areas, wish to have an introduction to our topic.

  14. Higher critical current density achieved in Bi-2223 High-Tc superconductors

    OpenAIRE

    M. S. Shalaby; H.M. Hashem; T.R. Hammad; L.A. Wahab; K.H. Marzouk; Soltan, S.

    2016-01-01

    Bi2Sr2Ca2Cu3Ox (Bi-2223) were prepared using a solid state reaction method at different sintering times and temperatures. Structural phase identifications have been done using X-Ray analysis and refinement by Reitveld method which proves the coexistence of Bi-2223 and Bi-2212 phases. The critical transition temperature Tc and critical current density Jc values were measured using superconducting quantum interference device magnetometer (SQUID) and by the magneto-optics technique. A remarkable...

  15. The electrical transport properties of high quality Bi-2223 crystal

    International Nuclear Information System (INIS)

    We have studied electrical transport properties of a high quality Bi2Sr2Ca2Cu3O10+x crystal below a superconducting critical temperature, Tc. In magnetic fields B parallel to the c axis just above a voltage response onset resistance versus temperature data are well fitted to the vortex-glass model. Obtained from the vortex-glass analysis, a melting transition boundary for Bi-2223 crystal is shifted towards lower temperatures compared to previously reported data for a (Bi, Pb)-2223 single crystal. The critical current density, Jc, of Bi-2223 crystals is close to Jc values presented elsewhere for Bi-2223 tapes, suggesting a principal role of weak intrinsic pinning properties of Bi-2223 as a main limiting factor of Jc of Bi-2223 conductors.

  16. PREFACE: Superconducting materials Superconducting materials

    Science.gov (United States)

    Charfi Kaddour, Samia; Singleton, John; Haddad, Sonia

    2011-11-01

    The discovery of superconductivity in 1911 was a great milestone in condensed matter physics. This discovery has resulted in an enormous amount of research activity. Collaboration among chemists and physicists, as well as experimentalists and theoreticians has given rise to very rich physics with significant potential applications ranging from electric power transmission to quantum information. Several superconducting materials have been synthesized. Crucial progress was made in 1987 with the discovery of high temperature superconductivity in copper-based compounds (cuprates) which have revealed new fascinating properties. Innovative theoretical tools have been developed to understand the striking features of cuprates which have remained for three decades the 'blue-eyed boy' for researchers in superconductor physics. The history of superconducting materials has been notably marked by the discovery of other compounds, particularly organic superconductors which despite their low critical temperature continue to attract great interest regarding their exotic properties. Last but not least, the recent observation of superconductivity in iron-based materials (pnictides) has renewed hope in reaching room temperature superconductivity. However, despite intense worldwide studies, several features related to this phenomenon remain unveiled. One of the fundamental key questions is the mechanism by which superconductivity takes place. Superconductors continue to hide their 'secret garden'. The new trends in the physics of superconductivity have been one of the two basic topics of the International Conference on Conducting Materials (ICoCoM2010) held in Sousse,Tunisia on 3-7 November 2010 and organized by the Tunisian Physical Society. The conference was a nice opportunity to bring together participants from multidisciplinary domains in the physics of superconductivity. This special section contains papers submitted by participants who gave an oral contribution at ICoCoM2010

  17. 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.

  18. 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.

  19. 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...

  20. 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$^{−1}$).

  1. Superconducting magnets

    Energy Technology Data Exchange (ETDEWEB)

    1994-08-01

    This report discusses the following topics on superconducting magnets: D19B and -C: The next steps for a record-setting magnet; D20: The push beyond 10 T: Beyond D20: Speculations on the 16-T regime; other advanced magnets for accelerators; spinoff applications; APC materials development; cable and cabling-machine development; and high-{Tc} superconductor at low temperature.

  2. Josephson plasma resonance in superconducting multilayers

    DEFF Research Database (Denmark)

    Pedersen, Niels Falsig; Sakai, S

    1998-01-01

    the recently derived plasma resonance phenomena for high-T-c superconductors of the Bi2Sr2CaCu2Ox type is discussed. Our approach allows us to give full details of the different plasma resonance excitations, and we also predict the existence of new nonlinear effects, so far only identified in single......We derive an analytical solution for the Josephson plasma resonance of superconducting multilayers. This analytical solution is derived mainly for low-T-c systems with magnetic coupling between the superconducting layers. but many features of our results are more general, and thus an application to...

  3. Superconductivity: actual stage forcasting and subsidies for national policy

    International Nuclear Information System (INIS)

    An overview on the situation of metallic superconductors, their applications and market, and a brief history about the superconductivity at high Tc (new ceramic superconductors), describing the actual level of research and development in the world and national plans are presented. Some comments about incentives and markets for rare earths are done. The scientific and technological challengers are discussed and some suggestions to lead a superconductivity national program are proposed. (M.C.K.)

  4. X-ray thermal and magnetic study of superconducting Bi1.6Pb0.4Sr2Ca2Cu3Ox as a function of O2/N2 ratio in reaction atmosphere

    International Nuclear Information System (INIS)

    This paper reports on samples of Pb-doped BSCCO that were prepared under flowing O2 + N2 mixtures in variable ratios. X-ray diffraction shows a non-monotone change of lattice constants and of 212/2223 phase proportion with atmosphere composition, consistently with magnetic measurements. A high O2 content worsens heavily the superconducting properties. DTA results prove that all samples transform into 2201 phase just below melting, and allow to optimize the thermal treatment during preparation

  5. SUPERCONDUCTING PHOTOINJECTOR

    Energy Technology Data Exchange (ETDEWEB)

    BEN-ZVI,I.; BURRILL, A.; CALAGA, R.; CHANG, X.; GROVER, R.; GUPTA, R.; HAHN, H.; HAMMONS, L.; KAYRAN, D.; KEWISCH, J.; LAMBIASE, R.; LITVINENKO, V.; MCINTYRE, G.; NAIK, D.; PATE, D.; PHILLIPS, D.; POZDEYEV, E.; RAO, T.; SMEDLEY, J.; THAN, R.; TODD, R.; WEISS, D.; WU, Q.; ZALTSMAN, A.; ET AL.

    2007-08-26

    One of the frontiers in FEL science is that of high power. In order to reach power in the megawatt range, one requires a current of the order of one ampere with a reasonably good emittance. The superconducting laser-photocathode RF gun with a high quantum efficiency photocathode is the most natural candidate to provide this performance. The development of a 1/2 cell superconducting photoinjector designed to operate at up to a current of 0.5 amperes and beam energy of 2 MeV and its photocathode system are the subjects covered in this paper. The main issues are the photocathode and its insertion mechanism, the power coupling and High Order Mode damping. This technology is being developed at BNL for DOE nuclear physics applications such as electron cooling at high energy and electron ion colliders..

  6. X-ray photoelectron study of the valence state of iron in iron-containing single-crystal (BiFeO3, PbFe1/2Nb1/2O3), and ceramic (BaFe1/2Nb1/2O3) multiferroics

    International Nuclear Information System (INIS)

    Research highlights: → Fe2p, Fe3p, and Fe3s XPS in single-crystal BiFeO3 and PbFe1/2Nb1/2O3, are measured. → Single-crystal multiferroics and Fe2O3 have the Fe ions only in the Fe3+ valence state. → BaFe1/2Nb1/2O3 ceramic samples with various Fe2+/Fe3+ abundances are synthesized. → An approximate method to determine the Fe2+/Fe3+ abundances is suggested. -- Abstract: Fe2p, Fe3p, and Fe3s X-ray photoelectron spectra (XPS) are measured with high resolution in single-crystal multiferroics BiFeO3 and PbFe1/2Nb1/2O3, as well as in reference samples Fe2O3, FeSO4.7H2O, FeC2O4.2H2O. The spectra are assigned based on an isolated-ion approximation calculation. Single-crystal multiferroics and Fe2O3 are shown to have the Fe ions only in the Fe3+ valence state. Ceramic samples of BaFe1/2Nb1/2O3 with various relative Fe2+/Fe3+ abundances are synthesized in various conditions. An approximate method to determine the Fe2+/Fe3+ ratio in a sample is suggested. The method is based on the fitting of the sample's 2p XPS with a superposition of Fe2+ and Fe3+ 2p spectra. An effect of temperature regimes of sintering and annealing on the Fe2+/Fe3+ ratio is demonstrated.

  7. Oxygen octahedra distortion induced structural and magnetic phase transitions in Bi{sub 1−x}Ca{sub x}Fe{sub 1−x}Mn{sub x}O{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Pawan; Kar, Manoranjan, E-mail: mano@iitp.ac.in [Department of Physics, Indian Institute of Technology Patna, Patna 800013 (India); Shankhwar, Nisha; Srinivasan, A. [Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781039 (India)

    2015-05-21

    The co-doping of Ca and Mn in respective Bi and Fe-sites of BiFeO{sub 3} lattice leads to structural transition from rhombohedral (R3c space group) to orthorhombic (Pbnm space group) crystal symmetry. The tilt angle for anti-phase rotation of the oxygen octahedra of BiFeO{sub 3} at room temperature is observed to be ∼13.8°. It decreases with the increase in the co-doping percentage which suggests the composition-driven structural phase transition. The remnant magnetization for sample with 15% of co-doping becomes about 16 times that of BiFeO{sub 3}. It may be attributed to the suppression of cycloid spin structure and uncompensated spins at the surface of nanocrystallites. Further increase in co-doping percentage results in the sharp reduction of remnant magnetization due to the dominant contribution from the collinear antiferromagnetic ordering in the Pbnm space group. The Arrott plot analysis clearly indicates the composition-driven crossover from the antiferromagnetic to weak ferromagnetic ordering and vice versa. Electron spin resonance results provide the evidence for the composition-driven phase transitions from an incommensurate spin cycloidal modulated state to one with nearly homogeneous spin order. The band gap (2.17 eV) of BiFeO{sub 3} measured using UV-Vis spectra was supported by the resonance Raman spectra.

  8. Ac-dc conversion effect in Y-Ba-Cu-O ceramics

    International Nuclear Information System (INIS)

    In Y-Ba-Cu-O ceramics, the dc voltage (V/sub dc/ ) induced by an rf current of 2--20 MHz, which had been previously reported as ''reverse ac Josephson effect,'' was observed at 77--300 K. The observed V/sub dc/ is not found to be due to reverse ac Josephson effect but due to nonlinear current-voltage characteristics, as in the case of BaPb/sub 1-//sub x/Bi/sub x/O3. However, behavior of the V/sub dc/ is different from that in BaPb/sub 1-//sub x/Bi/sub x/O3, which was related to bulk superconducting transition. The V/sub dc/ is observed only in the sample with particular electrical contacts and only when the rf current can flow through the potential electrical contacts. The origin of the rf-to-dc conversion effect in Y-Ba-Cu-O is ascribed to local nonlinear resistance near potential contacts

  9. 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.

  10. 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.

  11. Emission of the THz waves from large area mesas of superconducting Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+δ} by the injection of spin polarized current

    Energy Technology Data Exchange (ETDEWEB)

    Turkoglu, F., E-mail: fulyaturkoglu@iyte.edu.tr [Department of Physics, Izmir Institute of Technology, 35430 Urla Izmir (Turkey); Ozyuzer, L.; Koseoglu, H.; Demirhan, Y. [Department of Physics, Izmir Institute of Technology, 35430 Urla Izmir (Turkey); Preu, S.; Malzer, S. [Max Planck Optics Group, University of Erlangen-Nurnberg, Erlangen (Germany); Simsek, Y. [Physical Institute III, University of Erlangen-Nurnberg, Erlangen (Germany); Wang, H.B. [National Institute for Materials Science, Tsukuba (Japan); Muller, P. [Physical Institute III, University of Erlangen-Nurnberg, Erlangen (Germany)

    2013-08-15

    Highlights: ► THz emission was achieved from as-grown mesas due to injection of spin polarized current. ► Bump in return branch of I–V curve was observed due to radiation. ► The necessity of adjustment of doping level for THz emission was eliminated. -- Abstract: Rectangular Au/Co/Au/Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+δ} (Bi2212) mesa structures with large areas and high thicknesses were fabricated on as-grown Bi2212 single crystals in order to obtain small critical current from as-grown mesas by the injection of spin polarized current and so eliminate the adjustment of doping level for successful THz emission. We have performed c-axis resistance versus temperature (R–T), current–voltage (I–V) characteristics and bolometer measurements. It is the first time that THz emission has been observed from as-grown mesas due to injection of spin polarized current.

  12. 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.

  13. 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.

  14. In situ observations of crack formation in multi-filament Bi-2223 HTS tapes

    DEFF Research Database (Denmark)

    Sørensen, Bent F.; Horsewell, Andy; Skov-Hansen, P.

    2002-01-01

    High temperature superconducting tapes (BSCCO filaments embedded in Ag) were subjected to Uniaxial tension in an environmental scanning electron microscope, allowing in situ observation of cracking of the ceramic filaments. The first cracks were found to appear in the ceramic filaments at a strain...

  15. Microwave dynamics of YBCO bi-epitaxial Josephson structures

    DEFF Research Database (Denmark)

    Constantinian, K. Y.; Ovsyannikov, G. A.; Mashtakov, A. D.;

    1996-01-01

    The processes of interaction of microwaves (frequency View the MathML source) with a single high-Tc superconducting YBa2Cu3Ox (YBCO) bi-epitaxial grain-boundary junction and with an array of two junctions connected in series, have been investigated experimentally at temperatures T = 4.2− 77 K......, as well as the subharmonic detector response at weak magnetic fields φ microwave field induced frequency synchronization of two series connected bi-epitaxial YBCO junctions....

  16. 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.

  17. Tailored ceramics

    International Nuclear Information System (INIS)

    In polyphase tailored ceramic forms two distinct modes of radionuclide immobilization occur. At high waste loadings the radionuclides are distributed through most of the ceramic phases in dilute solid solution, as indicated schematically in this paper. However, in the case of low waste loadings, or a high loading of a waste with low radionuclide content, the ceramic can be designed with only selected phases containing the radionuclides. The remaining material forms nonradioactive phases which provide a degree of physical microstructural isolation. The research and development work with polyphase ceramic nuclear waste forms over the past ten years is discussed. It has demonstrated the critical attributes which suggest them as a waste form for future HLW disposal. From a safety standpoint, the crystalline phases in the ceramic waste forms offer the potential for demonstrable chemical durability in immobilizing the long-lived radionuclides in a geologic environment. With continued experimental research on pure phases, analysis of mineral analogue behavior in geochemical environments, and the study of radiation effects, realistic predictive models for waste form behavior over geologic time scales are feasible. The ceramic forms extend the degree of freedom for the economic optimization of the waste disposal system

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Effects of Fe{sub 2}O{sub 3} addition on the piezoelectric and the dielectric properties of 0.99Pb(Zr{sub 0.53}Ti{sub 0.47})O{sub 3}-0.01Bi(Y{sub 1-x}Fe{sub x})O{sub 3} ceramics for energy-harvesting devices

    Energy Technology Data Exchange (ETDEWEB)

    Mahmud, Iqbal; Ur, Soonchul; Yoon, Mansoon [Korea National University of Transportation, Chungju (Korea, Republic of)

    2014-07-15

    The 0.99Pb(Zr{sub 0.53}Ti{sub 0.47})O{sub 3}-0.01Bi(Y{sub 1-x}Fe{sub x})O{sub 3} [PZT-BYF(x)] (x = 0.0 - 0.6) piezoelectric ceramics have been synthesized by using a modified conventional solid-state method. Initially, the perovskite Pb(Zr{sub 0.53}Ti{sub 0.47})O{sub 3} (PZT) and the cubic-phase Bi(Y{sub 1-x}Fe{sub x})O{sub 3} [BYF(x)] were presynthesized and mixed to prepare PZT-BYF(x) ceramic composites. The effects of BYF(x) addition on the phase formation, microstructure, and piezoelectric/dielectric properties were measured as functions of sintering temperature. In addition to these measurements, the piezoelectric voltage constant (g{sub 33}) and the piezoelectric transduction coefficient (d{sub 33} x g{sub 33}) were measured in order to evaluate the essential criteria for an energy-harvesting material. For all the specimens, X-ray diffraction analyses showed a complete solid solution with co-existing tetragonal and rhombohedral perovskite phases. All the ceramics exhibited denser and finer microstructures, which produced a high relative density of ≥ 98%. Scanning electron microscopy (SEM) observations revealed that BYF(x) addition enhanced the sintering density through the formation of a liquid phase. The doping with BYF(x) in the PZT system was found to be effective for maintaining a high Curie temperature of around 377 - 390 .deg. C. With increasing content of Fe{sub 2}O{sub 3} in the BYF(x) system, the piezoelectric and the dielectric properties were significantly improved. At a sintering temperature of 1170 .deg. C, the piezoelectric and the dielectric properties of PZT-BYF(x) ceramics showed desirable values; this resulted in a significantly higher transduction coefficient. The compositions of PZTBYF(0.1), PZT-BYF(0.2), and PZT-BYF(0.3) showed a considerably lower ε{sup T}{sub 33} value, but higher d{sub 33} and k{sub p} values. Therefore, within the concentration limit of x = 0.1 to 0.3 moles of Fe{sub 2}O{sub 3}, the g{sub 33} and the d{sub 33} x g

  3. 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.

  4. Bi-based superconductors fabricated in high magnetic fields

    Institute of Scientific and Technical Information of China (English)

    LU X Y; A. NAGATA; K. SUGAWARA; K. WATANABE; T. NOJIMA

    2006-01-01

    The microstructure and superconducting properties of Bi-2223 superconductor fabricated in high magnetic fields were investigated. The results shows that the Bi-2212 grains with their c-axis parallel to the magnetic field were formed after the partial-melting and solidification in 8 T magnetic field,and transformed into the Bi-2223 grains with c-axis alignment during the further sintering process at 840 ℃ without magnetic field. The conversion of Bi-2212 grains to Bi-2223 grains has the heredity in grain alignment. The mixed structures of the Bi-2223 and the Bi-2212 grains with their c-axis parallel to the magnetic field are formed in samples sintered at 850-855 ℃ in 10 T magnetic field. When sintered in 10 T below 845 ℃,a high proportion of Bi-2223 phase is obtained,however no preferred orientation is observed. The Bi-2223 grains with their c-axis parallel to the axial direction of the vertical tube furnace are formed not only on the surface,but also in the center of the sample sintered at 850 ℃ for 120 h in a 15 ℃/cm temperature gradient without magnetic field. Moreover,the samples sintered in the temperature gradient and in a 10 T magnetic field have a stronger c-axis alignment of Bi-2223 phase.

  5. 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.

  6. 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.

  7. 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...

  8. Low-energy neutron irradiation on Bi-based (2223 Ag superconductors

    Directory of Open Access Journals (Sweden)

    H Najafpour

    2009-08-01

    Full Text Available  Bi-based and Ag-doped superconductors were irradiated by neutrons. Experimental result showed that XRD patern-intensity of irradiated Bi-based sample was decreased and The Tc of these samples were decreased by 7-10 K. The neutron irradiated sample was also found to decrease by 50% the normal state resistivity of samples. Therefore, neutron irradiation is a useful method to improve the superconductivity behavior of Bi-based materials.

  9. 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.

  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. Non-destructive evaluation of defects in ferromagnetic plates using a sensitive magnetic sensor based on second harmonic response of superconducting Bi1.6Pb0.4Sr2Ca2Cu3O10+ pellet

    Indian Academy of Sciences (India)

    Abhijit Ray; T K Dey

    2002-04-01

    The characteristics of a magnetic sensor, based on the non-linear electromagnetic response of the weak links present in polycrystalline BPSCCO superconductor are reported. The second harmonic response of the sensor in an alternating magnetic field at 40 kHz and at 77 K being a strong linear function of low d.c. field is utilized for magnetic field sensing. The noise limited resolution of the sensor is found to be 3.16 × 10-9 T/√ Hz for a.c. = 16 G and frequency 40 kHz. The magnetic sensor has been applied for non-destructive detection of various types of flaws in ferromagnetic plates and also for detection of small magnetic inclusions in a non-magnetic matrix. Our results suggest that the 2 response based BPSCCO superconductive magnetometer has potential for its appication in the area of non-destructive evaluation of defects in ferromagnetic materials.

  12. 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.

  13. Thin film processing for high-Tc superconductors of Bi-system

    International Nuclear Information System (INIS)

    Basic thin film deposition processes for the high-Tc superconductors of Bi-systems are described. There appear several superconducting phases including the low-Tc phase Bi2Sr2Ca1Cu2Ox and the high-Tc phase Bi2Sr2Ca2Cu3Ox. Thin films with these superconducting phases are synthesized by a selection of the substrate temperature Ts during the deposition: the high-Tc phase with Tc = 80K, at Ts < 600 degrees C. However, these films often comprise show structure comprising the different superconducting phases. The close control of the superconducting phase has been achieved by the layer-by-layer deposition in the atomic layer epitaxy process

  14. Quantum terahertz electronics (QTE) using coherent radiation from high temperature superconducting Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+δ} intrinsic Josephson junctions

    Energy Technology Data Exchange (ETDEWEB)

    Kadowaki, Kazuo, E-mail: kadowaki@ims.tsukuba.ac.jp [Division of Materials Science, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); CREST, Japan Science and Technology Agency, K’s 5-bancho, 7, 5-Bancho,Chiyoda-ku, Tokyo 102-0076 (Japan); WPI (World Premier Initiative)-MANA (Materials Nanoarchitechtonics), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Tsujimoto, Manabu; Delfanazari, Kaveh; Kitamura, Takeo; Sawamura, Masashi [Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); CREST, Japan Science and Technology Agency, K’s 5-bancho, 7, 5-Bancho,Chiyoda-ku, Tokyo 102-0076 (Japan); WPI (World Premier Initiative)-MANA (Materials Nanoarchitechtonics), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Asai, Hidehiro [Electronics and Photonics Research Institute, The National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Yamamoto, Takashi [Semiconductor Analysis and Radiation Effects Group, Japan Atomic Energy Agency, Gunma 370-1292 (Japan); Ishida, Kazuya; Watanabe, Chiharu; Sekimoto, Shunsuke; Nakade, Kurama; Yasui, Takaki; Asanuma, Kentaro [Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); CREST, Japan Science and Technology Agency, K’s 5-bancho, 7, 5-Bancho,Chiyoda-ku, Tokyo 102-0076 (Japan); WPI (World Premier Initiative)-MANA (Materials Nanoarchitechtonics), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); and others

    2013-08-15

    Highlights: • An attempt to Quantum Terahertz Electronics (QTE) has been made by improving IJJ characteristics. • High power THz emission was observed in a stand-alone type of rectangular mesa up to about 30 mW. • For higher power emission impedance matching between the mesa and vacuum should be realised. • Strong emission occurs only when the ac-Josephson effect and the cavity resonance work together. -- Abstract: An attempt has been made to improve THz radiation characteristics emitted from mesas made from Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+δ} single crystals in order to achieve an ultimate goal of high frequency quantum device applications, named here as the Quantum Terahertz Electronics (QTE). Among many requirements to be fulfilled and necessary for the development, we here made an effort to generate more intense radiation using a stand-alone type of mesa. Some characteristic features are described.

  15. 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.

  16. 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

  17. Superconductivity in Bismuth. A New Look at an Old Problem.

    Directory of Open Access Journals (Sweden)

    Zaahel Mata-Pinzón

    Full Text Available 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.

  18. Modeling constrained sintering of bi-layered tubular structures

    DEFF Research Database (Denmark)

    Tadesse Molla, Tesfaye; Kothanda Ramachandran, Dhavanesan; Ni, De Wei;

    2015-01-01

    Constrained sintering of tubular bi-layered structures is being used in the development of various technologies. Densification mismatch between the layers making the tubular bi-layer can generate stresses, which may create processing defects. An analytical model is presented to describe...... the densification and stress developments during sintering of tubular bi-layered samples. The correspondence between linear elastic and linear viscous theories is used as a basis for derivation of the model. The developed model is first verified by finite element simulation for sintering of tubular bi-layer system....... 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...

  19. 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.

  20. 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.)

  1. Study by neutrons diffusion and X-rays of structural and magnetic properties of Bi{sub 2}Sr{sub 2}Ca{sub n-1}Cu{sub n}O{sub 2n+4+{delta}} type superconductive cuprates; Etude par diffusion des neutrons et des rayons X des proprietes structurales et magnetiques des cuprates supraconducteurs de type Bi{sub 2}Sr{sub 2}Ca{sub n-1}Cu{sub n}O{sub 2n+4+{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Vasiliu-Doloc, L.

    1995-09-22

    In this work we have used inelastic and elastic neutron and X-ray scattering techniques for characterizing the incommensurate structural distortions in compounds belonging to the family Bi{sub 2}Sr{sub 2}Ca{sub n-1}Cu{sub n}O{sub 2n+4+{delta}} of high-Tc superconducting cuprates. We have searched the existence of structural instabilities specific of the CuO{sub 2} planes and of magnetic instabilities. The modulated structure of the 2212 phase has been refined from single-crystal neutron diffraction results and importance of distortion of CuO{sub 2} planes has thus been determined. It is shown that the additional oxygen is not ordered three-dimensionally within the modulated structure and that the information about it is contained in diffuse scattering results. A model of the short-range order associated with additional oxygen atoms is proposed and discussed. The temperature studies of the long-range order have shown a great stability of the amplitude and period of the incommensurate distortion wave in the one-layer, as well as in the double-layer compounds, either superconducting or insulating. We find such a behaviour to be highly incompatible with a distortion resulting from a charge-density-wave instability. The results we have obtained indicate that the bismuth-based high-Tc superconducting cuprates have essentially the same physics of the CuO{sub 2} planes as the previous two families, La{sub 2-x}Sr{sub x}CuO{sub 4} and YBa{sub 2}Cu{sub 3}O{sub 6+{delta}}, being at the proximity of three instabilities: a metal-insulator transition, an antiferromagnetic instability and a structural instability specific of the CuO{sub 2} planes. (author).

  2. The influence of oxygen deficiency and the unbalance Bi/Sr in Bi2Sr2CuO6+δ on metal- insulator transition

    International Nuclear Information System (INIS)

    Epitaxial Bi:2201 superconducting thin films (Tc ∼ 7K) with the composition Bi:Sr:Cu=2:1.95:1.01 and Bi:Sr:Cu=2.1:2:1.01 were deposited onto SrTiO3 substrate by using different partial oxygen pressures (f02) in the DC magnetron sputtering system. The compositions and structural characterization of the deposited films were carried out by (EDX), and X-ray diffraction measurements. The effect of Bi excess, Sr deficiency and the partial oxygen pressure in the sputtering gas on the metal-insulator transition are presented from the electrical resistivity data.

  3. 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

  4. Piezoelectric bismuth titanate ceramics for high temperature applications

    OpenAIRE

    Shulman, Holly Sue; Setter, Nava

    2005-01-01

    Bismuth titanate (Bi4Ti3O12) shows promise in piezoelectric applications in a temperature range (300-600 °C) which is not well served by standard piezoelectric ceramics. The proposal to use bismuth titanate ceramics for these applications has a major flaw, namely that the high electrical conductivity precludes the efficient polarization of these materials in an electric field. The degree of polarization is critical since it is directly related to the piezoelectric response. In addition, once ...

  5. 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}.

  6. 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.

  7. Defect structures in ceramic superconductors

    International Nuclear Information System (INIS)

    The influence of the defect structure on the superconducting properties of high temperature superconductors has been studied experimentally and by computer simulation technique. The relation between defect structure and the superconducting transition temperature, Tc, has been studied in Co-doped YBCO (YBa2Cu3-yCoyO6+x, 0 ≤ y ≤ 0.5), and it has been shown that th model, which has been established to account for the influence of oxygen ordering on Tc in oxygen deficient YBCO (YBa2Cu3O6+x, x 1.85Ce0.15CuO4+x have been carried out in order to elucidate why this material apparently is an electron conductor in the superconducting phase, and not as the other high temperature superconductors, a hole conductor. Structural studies on Pb2Sr2Y1-xCaxCu3O8 (0 ≤ x ≤ 0.5) have been carried out by neutron powder diffraction and it has been shown how the Ca-stoichiometry influence the Cu-valence in the superconducting CuO2-planes. The structural ordering of epitaxial thin films of YBCO and Bi2Sr2CaCu2O8+x deposit on heated substrates of SrTiO3, MgO, LaAlO3 and NdGaO3 has been studied by x-ray diffraction and Rutherford Backscattering spectroscopy, and the structural ordering has been analysed in relation to the superconducting properties. (au) (9 ills., 10 refs.)

  8. Synthesis and refinement of ferroelectric ceramic BaBi{sub 4}Ti{sub 4}O{sub 15} (BBT) using Rietveld Methods; Sintese e refinamento da ceramica ferroeletrica BaBi{sub 4}TI{sub 4}O{sub 15} (BBT) utilizando o Metodo Rietveld

    Energy Technology Data Exchange (ETDEWEB)

    Silva, P.M.O.; Sales, A.J.M.; Carneiro, J.C.S., E-mail: paulo2003@gmail.com [Universidade Federal do Ceara (DETI/UFC), Fortaleza, CE (Brazil). Dept. de Teleinformatica; Sancho, E.O. [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil). Dept. de Engenharia Metalurgica e de Materiais; Sales, J.C. [Universidade Estadual Vale do Acarau (UVA), Fortaleza, CE (Brazil). Dept. de Engenharia; Sombra, A.S.B. [Universidade Federal do Ceara (LOCEM/UFC), Fortaleza, CE (Brazil). Dept. de Fisica. Lab. de Telecomunicacoes e Ciencias e Engenharia de Materiais

    2012-07-01

    The lead zirconate titanate (PZT) has potential application in nonvolatile ferroelectric memory and capacitors, however this material is linked to environmental pollution. In order to remedy this problem, we propose the synthesis of the compound, BaBi{sub 4}TI{sub 4}O{sub 15} (BBT) because of similarity to PZT. The phase of the BBT has been prepared by the method of solid state. Reagents (BaCO{sub 3}, Bi{sub 2}O{sub 3} and TiO{sub 2}) were ground for 6 hours at 360 rpm in a planetary ball mill and suffered high energy heat treatment for 2 hours at temperatures of 850, 900, 950 and 1000 ° C. The calcined powder was characterized by X-ray diffraction (XRD) and refined by the program DBWSTools 2.3 Beta based on the Rietveld method. The results obtained confirmed the refinement of the single-phase with tetragonal structure BaBi{sub 4}TI{sub 4}O{sub 15} for all samples. The sample calcined at 950 °C presented the best densification (7.508 g/cm³). (author)

  9. Dielectric and AC conductivity studies of Nd substituted 0.8BaTiO3-0.2(Bi0.5(1-x)Nd0.5xK0.5)TiO3 lead free ceramics

    Science.gov (United States)

    Ramesh, M. N. V.; Ramesh, K. V.

    2016-05-01

    0.8BaTiO3 - 0.2(Bi0.5(1-x)Nd0.5xK0.5)TiO3 (0.01 ≤ x ≤ 0.06) lead free ceramic materials have been prepared by solid state reaction method and followed by high energy ball milling process. X-ray diffraction studies confirm the tetragonal structure of the materials at room temperature. Lattice parameters and density are decreasing with increase of Nd substitution. Microstructure studies were done by using Scanning electron microscope and it found that grain size is decreasing with increase of Nd substitution. Temperature and frequency dependent dielectric studies reveal relaxor behaviour of the materials. Dielectric constant, dielectric loss and Curie temperature are decreasing with Nd substitution. Maximum Curie temperature of 195°C was observed at 1MHz for x=0.01 Nd substituted sample. Degree of diffuseness was calculated from the modified Curie-Weiss law and it is increasing with Nd substitution. AC conductivity is increasing with increase of Nd substitution and observed maximum activation energy of 0.52 eV for x=0.02 Nd substituted sample.

  10. 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.

  11. 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.

  12. 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.

  13. Optical properties of Dy3+ doped bismuth zinc borate glass and glass ceramics

    Science.gov (United States)

    Shanmugavelu, B.; Kanth Kumar, V. V. Ravi

    2012-06-01

    Dy3+ doped bismuth zinc borate transparent glasses were prepared by melt quenching technique and these glasses were used precursor to obtain transparent glass ceramics by heat treatment method. XRD pattern of the glass ceramic shows the formation of the β-BiB3O6 and Bi2ZnOB2O6 phases. The visible emission intensity of the glass ceramics is stronger than the glass. This can be due to the formation of nano nonlinear optical crystallites in glass matrix.

  14. 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.

  15. 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.

  16. 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)

  17. Synthesis and characterization by diffraction of X-Ray and impedance spectroscopy the ferroelectric ceramic Ti{sub 0.4}Fe{sub 0.3}Nb{sub 0.3}O{sub 2} (TFNO) with additions of Bi{sub 2}O{sub 3}; Sintese e caracterizacao por difracao de raios-X e espectroscopia de impedancia da ceramica ferroeletrica Ti{sub 0.4}Fe{sub 0.3}Nb{sub 0.3}O{sub 2} (TFNO) com adicoes de Bi{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Sousa, D.G.; Sales, A.J.M.; Carneiro, J.C.S.; Sancho, E.O.; Sombra, A.S.B., E-mail: djfisica@gmail.com [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil); Sales, J.C. [Universidade Estadual Vale do Acarau (UVA), Fortaleza, Ceara, CE (Brazil). Departamento de Engenharia

    2012-07-01

    The ceramic Ti{sub 0.4F}e{sub 0.3}Nb{sub 0.}3O{sub 2} (TFNO), was synthesized through of the solid-state reaction technique. The oxides were mixed for 7h and calcined at 1075 deg C for 4h. Phase TFNO was confirmed via X-ray diffraction technique (XRD) and Rietveld refinement. Were made additions of 6% and 8% of Bi{sub 2}O{sub 3} to the calcined powder, that after the pressing and sintering at 1125 deg C, were submitted to analysis by XRD and impedance spectroscopy study. The X-ray diffraction technique confirm a rutile-type structure [TiO2 (tP6) ] to calcined powder and to presence of two phases, Ti0.4Fe0.3Nb0.3O2 (TFNO tetragonal-rutile P 42/m n m(136)) and Bi1.721Fe1.056Nb1.134O7 (BFNO cubic F d -3 m Z(227)), for samples sintered. The impedance spectroscopy reveal in 240°C, to TFNO with addition of 8% at 100 KHz, the following results: σ' = 0,0452(Ω.m){sup -1}; ε{sub r}{sup '} = 9613 e tgδ = 0,83556. (author)

  18. 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.

  19. 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...

  20. Preparation and Poikilothermic Dielectric Spectrum Studies of Ferroelectric Ceramics Bi0.04Sr0.94TiO3%Bi0.04Sr0.94TiO3铁电陶瓷的合成与变温介电谱研究

    Institute of Scientific and Technical Information of China (English)

    李泽; 周恒为; 张晋鲁; 黄以能; 尹红梅; 苏欣; 周树银; 马学静; 卫来; 周兰兰; 张文; 鹿桂花

    2010-01-01

    采用固相反应一次烧结成型的方法制备了Bi0.04Sr0.94TiO3弛豫铁电陶瓷,着重研究了烧结条件对陶瓷的外形和介电性能的影响.结果表明,适当的压力和粉末湿度能促进样品压制成型,较慢的升降温速率有利于样品受热均匀,优化陶瓷的外形,改善微观结构.变温低频介电谱测量分析表明,所合成的Bi0.04Sr0.94TiO3陶瓷样品的主相的确是弛豫铁电相,而且性能稳定.

  1. Development of high temperature superconducting materials for power applications

    International Nuclear Information System (INIS)

    The work presented in this thesis is directed towards two potential electrical power applications of high temperature superconductors: superconducting coils for magnetic field generation and superconducting power switches. The first systematic investigation into the bending strain tolerance of Ic in short lengths of Ag/Tl-1223 PIT tape is presented as a preliminary study into the required coil winding protocol for the fabrication of superconducting coils. Comparison of the microstructure with the bending strain tolerance of Ic for Ag/Tl-1223 tapes shows that the shape and degree of porosity and the grain size can explain many features of the experimental data. Monofilamentary in situ reacted Ag/Tl-1223 PIT tape has excellent bending strain tolerance up to strains of 1.5%. Superconducting coils of total tape length up to 5 m have been fabricated via a wind-and-react route using a dip coated refractory electrical insulation and tested at 77 K in different applied magnetic fields. The promising current transport properties of short lengths of Ag/Tl-1223 PIT tape are not transferred to these coils. There is strong evidence that this degradation is due to the self field limitation of Ic. Thick films of Bi-2212 on MgO substrates have been investigated for applications as superconducting power switches. The effects of the substrate format (single crystal or polycrystalline MgO) on the Bi-2212 thick film are discussed. The absence of grain boundaries and contaminants makes single crystal MgO the preferred substrate material. Variations in the heat treatment schedule and film thickness are shown to affect the long range grain connectivity and hence the reproducibility of Jc for Bi-2212 thick films on single crystal MgO. Processing details for the achievement of reproducible values of Jc (around 3000 Acm-2 ) are presented. The power switching characteristics of Bi-2212 thick films on single crystal MgO substrates have been investigated at liquid nitrogen temperatures. The

  2. Transport Barkhausen-like noise and flux-flow regime in Bi1.65Pb0.35Sr2Ca2Cu3O10+δ ceramic samples

    International Nuclear Information System (INIS)

    We report on the detection of transport Barkhausen-like noise (TBN) in polycrystalline samples of Bi1.65Pb0.35Sr2Ca2Cu3O10+δT=77K. Measurements of magnetization versus applied magnetic field performed in powder samples at the same temperature indicate that the grains have a Bean-like behavior. From this curve we were able to determine the first critical field of the grains Hclg∼80Oe and the full penetration field of the grains H*∼135Oe. Based on these results, the sample was subjected to an AC magnetic field with amplitude, Bmax=6mT and frequency, f=1Hz in order to avoid the flux penetration within the grains. Then, by using the standard DC four-probe method, the transport Barkhausen-like noise was measured for several values of excitation current. The results reveal that, under certain conditions, a noise in the voltage signal of the sample is clearly identified and related to the transition of the sample to the flux-flow regime. By using the Fast Fourier Transform (FFT) method, the power spectrum of TBN data is calculated and exhibits an 1/f2 frequency dependence, suggesting that the transition to the flux-flow regime in these materials is not a smooth process

  3. 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.

  4. Tl-based high temperature superconducting cuprates: structure and properties

    International Nuclear Information System (INIS)

    The structure and properties of the Tl-based high temperature superconducting cuprates are reviewed. The single Tl-O layered phases Tl(Sr/Ba)2Ca2Cu3O9 stabilized by substitution of Pb or Bi in the Tl site are being developed for technological applications, because of their high Tc, excellent magnetic flux pinning and minimal weak-link behavior. Some of the factors that affect the high temperature superconducting properties, including substitutions, electronic structure, oxygen nonstoichiometry and defects are discussed in relation to the structure. (orig.)

  5. Dental ceramics: An update

    OpenAIRE

    Shenoy Arvind; Shenoy Nina

    2010-01-01

    In the last few decades, there have been tremendous advances in the mechanical properties and methods of fabrication of ceramic materials. While porcelain-based materials are still a major component of the market, there have been moves to replace metal ceramics systems with all ceramic systems. Advances in bonding techniques have increased the range and scope for use of ceramics in dentistry. In this brief review, we will discuss advances in ceramic materials and fabrication techniques. Examp...

  6. 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.

  7. Synthesis of Bi2Sr2CaCu2Ox superconductors via direct oxidation of metallic precursors

    International Nuclear Information System (INIS)

    Bi2Sr2CaCu2Ox(Bi2212)/Ag multifilamentary wires are manufactured via the powder-in-tube process using oxide powders. After deformation, the wires undergo a partial-melt process, resulting in a complex, heterogeneous microstructure containing multiple secondary phases and porosity, limiting the wires’ electrical and mechanical performance. Here, an alternative approach using the direct conversion of metallic precursors (MPs) to Bi2212 is studied. The formation of metallic precursor powders via a mechanical alloy is discussed. The MP powder is then converted to superconducting Bi2212 through a simple two-step heat treatment. By introducing oxygen at a temperature at which Bi2212 is in a stable phase, and holding at an elevated temperature for a sufficient time, the metallic precursors are oxidized and transformed into Bi2212. Several factors that impact the formation and growth of Bi2212 grains are discussed. Peak temperature, holding time and heating rate are shown to affect the MP →Bi2212 conversion, the Bi2201 content and the Bi2212 morphology and density. It is found that Bi2Sr2CuOy (Bi2201) can be the only phase impurity after heat treatment, which is quite different from what is observed in partial-melt processed wires derived from oxide precursors. Lastly, the microstructure at the sample/silver interface suggests larger size and preferred orientation of Bi2212 grains with the aid of a silver surface. Implications for MP Bi2212 wires are discussed. (paper)

  8. 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.

  9. 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.

  10. 稀土氧化物掺杂ZnO-Bi2O3系压敏陶瓷的介电特性%The Dielectric Characteristics of Rare Earth Oxides Adulterate with ZnO-Bi2O3 Series Varistor Ceramics

    Institute of Scientific and Technical Information of China (English)

    成鹏飞; 李盛涛

    2010-01-01

    在不同温度下测量了稀土氧化物Gd2O3、Ce2O3掺杂ZnO-Bi2O3系压敏陶瓷的介电频谱,发现稀土氧化物的掺杂引起介电损耗显著增大.通过理论计算发现稀土氧化物掺杂后锌填隙和氧空位浓度显著增大,而耗尽层宽度明显减小.因此认为稀土氧化物引起施主性本征缺陷浓度的增大,导致Schottky势垒变薄,从而引起泄露电流的增大及非线性指数的下降.

  11. 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

  12. Superconductivity and its application

    International Nuclear Information System (INIS)

    This paper, after a short introduction to superconductivity and to multifilamentary superconducting composites is aiming to review the state of the art and the future perspective of some of the applications of the superconducting materials. The main interest is focussed to large scale applications like, for istance, magnets for accelerators or fusion reactors, superconducting system for NMR thomography, etc. A short paragraph is dedicated to applications for high sensitivity instrumentation. The paper is then concluded by some considerations about the potentialities of the newly discovered high critical temperature materials

  13. Structural properties of CaTi{sub 1-x}(Nb{sub 2/3}Li{sub 2/3}){sub x}O{sub 3-d}elta (CNLTO) and CaTi{sub 1-x}(Nb{sub 1/2}Ln{sub 1/2}){sub x}O{sub 3} (Ln=Fe (CNFTO), Bi (CNBTO)), modified dielectric ceramics for microwave applications

    Energy Technology Data Exchange (ETDEWEB)

    Costa, R.C.S. [Laboratorio de Telecomunicacoes e Ciencia e Engenharia dos Materiais (LOCEM), Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, CEP 60455-760, Fortaleza, Ceara (Brazil); Departamento de Engenharia de Teleinformatica, CP 6007, Universidade Federal do Ceara, CEP 60455-760, Fortaleza, Ceara (Brazil); Bruno Costa, A.D.S. [Departamento de Engenharia de Teleinformatica, CP 6007, Universidade Federal do Ceara, CEP 60455-760, Fortaleza, Ceara (Brazil); Freire, F.N.A.; Santos, M.R.P.; Almeida, J.S.; Sohn, R.S.T.M. [Laboratorio de Telecomunicacoes e Ciencia e Engenharia dos Materiais (LOCEM), Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, CEP 60455-760, Fortaleza, Ceara (Brazil); Sasaki, J.M. [Laboratorio de Raios-X, Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, CEP 60455-760, Fortaleza, Ceara (Brazil); Sombra, A.S.B., E-mail: sombra@fisica.ufc.b [Laboratorio de Telecomunicacoes e Ciencia e Engenharia dos Materiais (LOCEM), Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, CEP 60455-760, Fortaleza, Ceara (Brazil)

    2009-05-01

    This paper presents an investigation of the structural characteristics of Nb{sub 1/2}Bi{sub 1/2} (CNBTO), Nb{sub 1/2}Fe{sub 1/2} (CNFTO) and Nb{sub 2/3}Li{sub 1/3} (CNLTO) substitution into the B-site of calcium titanate ceramics. The modified CaTiO{sub 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{sup -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 alpha=7x10{sup -3}). The lowest value of k=25.7 (f=4.8 GHz) and tg alpha=3x10{sup -3}, was obtained for the CNFTO phase. These measurements confirm the possible use of such material for microwave devices like dielectric resonator antennas.

  14. The BiCu1-xOS oxysulfide: Copper deficiency and electronic properties

    Science.gov (United States)

    Berthebaud, D.; Guilmeau, E.; Lebedev, O. I.; Maignan, A.; Gamon, J.; Barboux, P.

    2016-05-01

    An oxysulfide series of nominal compositions BiCu1-xOS with xanalysis showing, in the Cu atomic columns, alternating peaks of different intensities in some very localized regions. For larger Cu deficiencies (x>0.05 in the nominal composition), other types of structural nanodefects are evidenced such as bismuth oxysulfides of the "BiOS" ternary system which might explain the report of superconductivity for the BiCu1-xOS oxysulfide. Local epitaxial growth of the BiCuOS oxysulfide on top of CuO is also observed. In marked contrast to the BiCu1-xOSe oxyselenide, these results give an explanation to the limited impact of Cu deficiency on the Seebeck coefficient in BiCu1-xOS compounds.

  15. Large magnetoresistance of MnBi/Bi/MnBi spin valve

    Energy Technology Data Exchange (ETDEWEB)

    Tarawneh, Khaldoun, E-mail: Khaldoun@psut.edu.jo [Princess Sumaya University for Technology, Amman 11941 (Jordan); Al-Aqtash, Nabil; Sabirianov, Renat [University of Nebraska at Omaha, Omaha, NE 68182 (United States)

    2014-08-01

    A transport magetoresistance (MR) of MnBi/Bi/MnBi spin valve device was calculated using density functional theory coupled with nonequilibrium Green's function method. The calculated transmission MR of the MnBi/Bi/MnBi spin valve device is around 750%, Obtained MR is very large compared with MR observed experimentally in MnBi junctions at room temperature (MR∼70%). Large MR is consistent with a large transport spin polarization was demonstrated in MnBi films by the point contact Andreev reflection spectroscopy. MR of experimental point contacts is observed to be low is probably due to the rough interfaces that increased scattering and contact resistance. Consequently, a spin-valve MnBi/Bi/MnBi device could potentially have large MR that could be controlled by varying the thickness of the Bi spacer. Thus, MnBi is a promising candidate for high MR devices with tunable spacer properties. - Highlights: • We calculate the transport magetoresistance (MR) of MnBi/Bi/MnBi spin valve device. • The calculated transmission MR of the MnBi/Bi/MnBi spin valve device is around 750%. • MR depend on the thickness of Bi layer. • MnBi is a promising candidate for high MR devices using spin polarizing current.

  16. Spray pyrolysis process for preparing superconductive films

    International Nuclear Information System (INIS)

    This paper describes a spray pyrolysis method for preparing thin superconductive film. It comprises: preparing a spray pyrolysis solution comprising Bi,Sr,Ca and Cu metals in a solvent; heating a substrate to a first temperature; spraying the solution onto the heated substrate to form a film thereon; heating the film and substrate to a second temperature of about 700 degrees-825 degrees C, the second temperature being higher than the first temperature; heating the film and substrate to a third temperature of about 870 degrees-890 degrees C to melt the film; once the film and substrate reach the third temperature, further heat treating the film and substrate; cooling the film and substrate to ambient temperature. This patent also describes a spray pyrolysis method for preparing thin superconductive films. It comprises: preparing a spray pyrolysis solution comprising Bi, Ca and Cu metals and fluxing agent in a solvent; heating a substrate to a first temperature; spraying the solution onto the heated substrate to form a film thereon; heating the film and substrate to a second temperature about 700 degrees-825 degrees C, the second temperature being higher than the first temperature; heating the film and substrate at a third temperature about 840 degrees-860 degrees C; and cooling the film and substrate to ambient temperature

  17. 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.

  18. 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...

  19. 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.

  20. 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.

  1. High temperature superconductivity

    International Nuclear Information System (INIS)

    This book covers the proceedings of the 3rd National Meeting on High Temperature Superconductivity Topics includes: Crystal growth of superconductors; thermodynamic stability of superconducting materials; spectroscopy of High Tc Superconductors; synchrotron radiation investigation of superconductors; density state determination; measurements of current density; preparation and characterization of superconductors

  2. Superconducting RF cavities

    CERN Document Server

    Bernard, Philippe

    1999-01-01

    It was 20 years ago when the research and development programme for LEP superconducting cavities was initiated. It lasted about 10 years. Today, my aim is not to tell you in great detail about the many innovations made thanks to our research, but I would like to point out some milestones in the development of superconducting cavities where Emilio's influence was particularly important.

  3. Fast granular superconducting bolometer

    International Nuclear Information System (INIS)

    A granular superconducting thin film bolometer made by anodizing a thin film of such materials as niobium nitride to form a thin granular film separated by and covered with the anodized oxide. The bolometer is cooled to its superconducting state and electrically connected to a biasing and detecting network. Its temporal response is better than 1 ns

  4. Superconducting wind turbine generators

    DEFF Research Database (Denmark)

    Abrahamsen, Asger Bech; Mijatovic, Nenad; Seiler, Eugen;

    2010-01-01

    , 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...

  5. Influence of Rare-earth Oxides on Distribution of Grain Size and Electrical Properties of ZnO-Bi2O3 Varistor Ceramics%稀土氧化物对ZnO-Bi2O3系压敏陶瓷晶粒分布及电气性能的影响

    Institute of Scientific and Technical Information of China (English)

    李盛涛; 成鹏飞; 王玉平; 朱斌

    2008-01-01

    研究了稀土氧化物Ce2O3、Gd2O3、La2O3、Y2O3对ZnO-Bi2O3系压敏陶瓷晶粒尺寸和电气性能的影响,结果表明,稀土氧化物可有效地抑制ZnO晶粒的生长,掺杂Ce2O3、Gd2O3、La2O3、Y2O3后,晶粒的主要分布分别为O~18μm、0~14μm、0~11μm、0~16μm;平均晶粒尺寸下降,其中掺杂Gd2O3,后晶粒尺寸最小,为6.2μm.ZnO晶粒分布的标准方差明显下降,改善了晶粒尺寸分布的均匀性.掺杂稀土氧化物后,电位梯度显著提高,ElmA达到了427.5V/mm,改善了ZnO压敏陶瓷的电气性能.

  6. Apparent vanishing of ferroelectricity in nanostructured BiScO3PbTiO3

    OpenAIRE

    Amorín, H.; R. Jiménez; Ricote, J.; Hungría, T; de Castro, A.; Algueró, M.

    2010-01-01

    Abstract Nanostructured ceramics of high-temperature piezoelectric 0.375BiScO 3 -0.625PbTiO 3 were prepared by spark plasma sintering of nanocrystalline powders obtained by mechanosynthesis. The macroscopic electrical properties were characterized on dense ceramics with decreasing average grain size down to 28 nm. Results indicate that the electric field is screened by the electrically insulating grain boundaries at the nanoscale, which needs to be considered when discussing size effects i...

  7. Pseudogap and proximity effect in the Bi2Te3/Fe1+yTe interfacial superconductor.

    Science.gov (United States)

    He, M Q; Shen, J Y; Petrović, A P; He, Q L; Liu, H C; Zheng, Y; Wong, C H; Chen, Q H; Wang, J N; Law, K T; Sou, I K; Lortz, R

    2016-01-01

    In the interfacial superconductor Bi2Te3/Fe1+yTe, two dimensional superconductivity occurs in direct vicinity to the surface state of a topological insulator. If this state were to become involved in superconductivity, under certain conditions a topological superconducting state could be formed, which is of high interest due to the possibility of creating Majorana fermionic states. We report directional point-contact spectroscopy data on the novel Bi2Te3/Fe1+yTe interfacial superconductor for a Bi2Te3 thickness of 9 quintuple layers, bonded by van der Waals epitaxy to a Fe1+yTe film at an atomically sharp interface. Our data show highly unconventional superconductivity, which appears as complex as in the cuprate high temperature superconductors. A very large superconducting twin-gap structure is replaced by a pseudogap above ~12 K which persists up to 40 K. While the larger gap shows unconventional order parameter symmetry and is attributed to a thin FeTe layer in proximity to the interface, the smaller gap is associated with superconductivity induced via the proximity effect in the topological insulator Bi2Te3.

  8. Ceramic Laser Materials

    Directory of Open Access Journals (Sweden)

    Guillermo Villalobos

    2012-02-01

    Full Text Available Ceramic laser materials have come a long way since the first demonstration of lasing in 1964. Improvements in powder synthesis and ceramic sintering as well as novel ideas have led to notable achievements. These include the first Nd:yttrium aluminum garnet (YAG ceramic laser in 1995, breaking the 1 KW mark in 2002 and then the remarkable demonstration of more than 100 KW output power from a YAG ceramic laser system in 2009. Additional developments have included highly doped microchip lasers, ultrashort pulse lasers, novel materials such as sesquioxides, fluoride ceramic lasers, selenide ceramic lasers in the 2 to 3 μm region, composite ceramic lasers for better thermal management, and single crystal lasers derived from polycrystalline ceramics. This paper highlights some of these notable achievements.

  9. Fatigue of dental ceramics

    OpenAIRE

    Zhang, Yu; Sailer, Irena; lawn, brian

    2013-01-01

    Clinical data on survival rates reveal that all-ceramic dental prostheses are susceptible to fracture from repetitive occlusal loading. The objective of this review is to examine the underlying mechanisms of fatigue in current and future dental ceramics

  10. Ceramic art in sculpture

    OpenAIRE

    Rokavec, Eva

    2014-01-01

    Diploma seminar speaks of ceramics as a field of artistic expression and not just as pottery craft. I presented short overview of developing ceramic sculpture and its changing role. Clay inspires design and touch more than other sculpture media. It starts as early as in prehistory. Although it sometimes seems that was sculptural ceramics neglected in art history overview, it was not so in actual praxis. There is a rich tradition of ceramics in the East and also in Europe during the renaissanc...

  11. Ceramic Laser Materials

    OpenAIRE

    Guillermo Villalobos; Jasbinder Sanghera; Ishwar Aggarwal; Bryan Sadowski; Jesse Frantz; Colin Baker; Brandon Shaw; Woohong Kim

    2012-01-01

    Ceramic laser materials have come a long way since the first demonstration of lasing in 1964. Improvements in powder synthesis and ceramic sintering as well as novel ideas have led to notable achievements. These include the first Nd:yttrium aluminum garnet (YAG) ceramic laser in 1995, breaking the 1 KW mark in 2002 and then the remarkable demonstration of more than 100 KW output power from a YAG ceramic laser system in 2009. Additional developments have included highly doped microchip lasers,...

  12. Superconductivity in aromatic hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Kubozono, Yoshihiro, E-mail: kubozono@cc.okayama-u.ac.jp [Research Laboratory for Surface Science, Okayama University, Okayama 700-8530 (Japan); Research Center of New Functional Materials for Energy Production, Storage and Transport, Okayama University, Okayama 700-8530 (Japan); Japan Science and Technology Agency, ACT-C, Kawaguchi 332-0012 (Japan); Goto, Hidenori; Jabuchi, Taihei [Research Laboratory for Surface Science, Okayama University, Okayama 700-8530 (Japan); Yokoya, Takayoshi [Research Laboratory for Surface Science, Okayama University, Okayama 700-8530 (Japan); Research Center of New Functional Materials for Energy Production, Storage and Transport, Okayama University, Okayama 700-8530 (Japan); Kambe, Takashi [Department of Physics, Okayama University, Okayama 700-8530 (Japan); Sakai, Yusuke; Izumi, Masanari; Zheng, Lu; Hamao, Shino; Nguyen, Huyen L.T. [Research Laboratory for Surface Science, Okayama University, Okayama 700-8530 (Japan); Sakata, Masafumi; Kagayama, Tomoko; Shimizu, Katsuya [Center of Science and Technology under Extreme Conditions, Osaka University, Osaka 560-8531 (Japan)

    2015-07-15

    Highlights: • Aromatic superconductor is one of core research subjects in superconductivity. Superconductivity is observed in certain metal-doped aromatic hydrocarbons. Some serious problems to be solved exist for future advancement of the research. This article shows the present status of aromatic superconductors. - Abstract: ‘Aromatic hydrocarbon’ implies an organic molecule that satisfies the (4n + 2) π-electron rule and consists of benzene rings. Doping solid aromatic hydrocarbons with metals provides the superconductivity. The first discovery of such superconductivity was made for K-doped picene (K{sub x}picene, five benzene rings). Its superconducting transition temperatures (T{sub c}’s) were 7 and 18 K. Recently, we found a new superconducting K{sub x}picene phase with a T{sub c} as high as 14 K, so we now know that K{sub x}picene possesses multiple superconducting phases. Besides K{sub x}picene, we discovered new superconductors such as Rb{sub x}picene and Ca{sub x}picene. A most serious problem is that the shielding fraction is ⩽15% for K{sub x}picene and Rb{sub x}picene, and it is often ∼1% for other superconductors. Such low shielding fractions have made it difficult to determine the crystal structures of superconducting phases. Nevertheless, many research groups have expended a great deal of effort to make high quality hydrocarbon superconductors in the five years since the discovery of hydrocarbon superconductivity. At the present stage, superconductivity is observed in certain metal-doped aromatic hydrocarbons (picene, phenanthrene and dibenzopentacene), but the shielding fraction remains stubbornly low. The highest priority research area is to prepare aromatic superconductors with a high superconducting volume-fraction. Despite these difficulties, aromatic superconductivity is still a core research target and presents interesting and potentially breakthrough challenges, such as the positive pressure dependence of T{sub c} that is clearly

  13. Study on Recovery Performance of High Tc Superconducting Tapes for Resistive Type Superconducting Fault Current Limiter Applications

    Science.gov (United States)

    kar, Soumen; Kulkarni, Sandeep; Dixit, Manglesh; Singh, Kuwar Pal; Gupta, Alok; Balasubramanyam, P. V.; Sarangi, S. K.; Rao, V. V.

    Recent advances in reliable production of long length high temperature superconducting (HTS) tapes have resulted in commercial application of superconducting fault current limiters (SFCLs) in electrical utility networks. SFCL gives excellent technical performance when compared to conventional fault current limiters. The fast self-recovery from normal state to superconducting state immediately after the fault removal is an essential criterion for resistive type SFCL operation. In this paper, results on AC over-current testing of 1st generation (1G) Bi2223 tapes and 2nd generation (2G) YBCO coated conductors operating at 77 K are reported. From these results, the recovery time is estimated for different available HTS tapes in the market. The current limiting tests have also been performed to study the effective current limitation. Further, the recovery characteristics after the current limitation are quantitatively discussed for repetitive faults for different time intervals in the range of 100 ms to few seconds.

  14. Bi Syndrome (Arthralgia Syndrome)

    Institute of Scientific and Technical Information of China (English)

    ZHANG En-qin

    2010-01-01

    @@ The word 'Bi' (痹) in Chinese means an obstruction.Bi Syndrome refers the syndrome characterized by the obstruction of qi and blood in the meridians due to the invasion of external pathogenic wind, cold and dampness, manifested as soreness, pain, numbness,heavy sensation, swelling of joints and limbs, limitation of movements and so on.

  15. Superconductivity in the Bi-Sr-Ca-Cu-O system

    Energy Technology Data Exchange (ETDEWEB)

    Malachevsky, M.T.; Esparza, D.A.; Ovidio, C.A. d' ; Malarria, J.; Oliber, E.; Fiscina, J. (Centro Atomico Bariloche, Rio Negro (Argentina))

    1989-12-01

    We have prepared samples with different compositions and heat treatments, replacing part of the bismuth by other heavy elements. By means of X-ray diffractometry we have analyzed the presence of the different phases formed in each case. We report the resistivity and inductive measurements and discuss the influence of the heat treatments and compositions in the quantity and stability of the phases. (orig.).

  16. The superconducting spin valve and triplet superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Garifullin, I.A., E-mail: ilgiz_garifullin@yahoo.com [Zavoisky Physical-Technical Institute, Kazan Scientific Center of Russian Academy of Sciences, 420029 Kazan (Russian Federation); Leksin, P.V.; Garif' yanov, N.N.; Kamashev, A.A. [Zavoisky Physical-Technical Institute, Kazan Scientific Center of Russian Academy of Sciences, 420029 Kazan (Russian Federation); Fominov, Ya.V. [L. D. Landau Institute for Theoretical Physics RAS, 119334 Moscow (Russian Federation); Moscow Institute of Physics and Technology, 141700 Dolgoprudny (Russian Federation); Schumann, J.; Krupskaya, Y.; Kataev, V.; Schmidt, O.G. [Leibniz Institute for Solid State and Materials Research IFW Dresden, D-01171 Dresden (Germany); Büchner, B. [Leibniz Institute for Solid State and Materials Research IFW Dresden, D-01171 Dresden (Germany); Institut für Festkörperphysik, Technische Universität Dresden, D-01062 Dresden (Germany)

    2015-01-01

    A review of our recent results on the spin valve effect is presented. We have used a theoretically proposed spin switch design F1/F2/S comprising a ferromagnetic bilayer (F1/F2) as a ferromagnetic component, and an ordinary superconductor (S) as the second interface component. Based on it we have prepared and studied in detail a set of multilayers CoO{sub x}/Fe1/Cu/Fe2/S (S=In or Pb). In these heterostructures we have realized for the first time a full spin switch effect for the superconducting current, have observed its sign-changing oscillating behavior as a function of the Fe2-layer thickness and finally have obtained direct evidence for the long-range triplet superconductivity arising due to noncollinearity of the magnetizations of the Fe1 and Fe2 layers. - Highlights: • We studied a spin switch design F1/F2/S. • We prepared a set of multilayers CoOx/Fe1/Cu/Fe2/S (S=In or Pb). • The full spin switch effect for the superconducting current was realized. • We observed its oscillating behavior as a function of the Fe2-layer thickness. • We obtained direct evidence for the long-range triplet superconductivity.

  17. Electromechanical characterization of superconducting wires and tapes at 77 K

    CERN Document Server

    Bjoerstad, Roger

    The strain dependency of the critical current in state-of-the-art cuprate high-temperature superconductors (HTS) has been characterized. A universal test machine (UTM) combined with a critical current measurement system has been used to characterize the mechanical and the superconducting properties of conductors immersed in an open liquid nitrogen dewar. A set-up has been developed in order to perform simultaneous measurements of the superconductor lattice parameter changes, critical current, as well as the stress and strain at 77 K in self-field in a high energy synchrotron beamline. The HTS tapes and wires studied were based on YBCO, Bi-2223 and Bi-2212. The YBCO tapes were produced by SuperPower and American Superconductors (AMSC). Two types of Bi-2223 tapes, HT and G, were produced by Sumitomo Electric Industries (SEI). The Bi-2212 wires were produced by Oxford Superconducting Technology (OST) using Nexans granulate precursor, before undergoing a specialized over pressure (OP) processing and heat treatmen...

  18. Mechanical characterisation of superconducting BSCCO powder and numerical modelling of the OPIT process

    DEFF Research Database (Denmark)

    Bech, Jakob Ilsted; Eriksen, Morten; Toussaint, F.;

    2000-01-01

    Silver/BSCCO composite superconducting tapes are produced using BSCCO-2212 ceramic powder. The manufacturing process implies a large number of forming operations including drawing and rolling. The numerical simulation of the flat rolling process is of a great interest to anticipate the shape of t...

  19. The secondary electron emission coefficient of the material for the superconducting cavity input coupler

    CERN Document Server

    Kijima, Y; Furuya, T; Michizono, S I; Mitsunobu, S; Noer, R J

    2002-01-01

    The secondary electron emission (SEE) coefficients have been measured, for materials used in the coupler for KEKB superconducting cavities, i.e. Copper, Stainless steel plated with Copper, Niobium and Ceramic. We show that the electron bombardment is effective in decreasing the SEE coefficient of the metal surfaces, and the TiN coating and window fabrication processes influence the secondary electron yield. (author)

  20. Tunneling in superconducting structures

    Science.gov (United States)

    Shukrinov, Yu. M.

    2010-12-01

    Here we review our results on the breakpoint features in the coupled system of IJJ obtained in the framework of the capacitively coupled Josephson junction model with diffusion current. A correspondence between the features in the current voltage characteristics (CVC) and the character of the charge oscillations in superconducting layers is demonstrated. Investigation of the correlations of superconducting currents in neighboring Josephson junctions and the charge correlations in neighboring superconducting layers reproduces the features in the CVC and gives a powerful method for the analysis of the CVC of coupled Josephson junctions. A new method for determination of the dissipation parameter is suggested.

  1. High temperature superconductivity

    International Nuclear Information System (INIS)

    New superconducting oxides and physical basis of the high-temperature superconductivity developed from 1979 till 1986 are reviewed. The analysis is based upon the concept of exchange amplification of electron-phonon interaction put forward by the author in 1964. Using the high-temperature superconductivity theory an approach to increasing the critical temperature of high-temperature superconductors (HTSC) is proposed along with the means for synthesis of HTSC with higher critical fields. The feasibility of HTSC implementation in the modern physical experiment technology is also considered, e.g. for detecting the magnetic monopoles. 35 refs.; 2 figs

  2. Superconductivity in doped insulators

    Energy Technology Data Exchange (ETDEWEB)

    Emery, V.J. [Brookhaven National Lab., Upton, NY (United States); Kivelson, S.A. [California Univ., Los Angeles, CA (United States). Dept. of Physics

    1995-12-31

    It is shown that many synthetic metals, including high temperature superconductors are ``bad metals``, with such a poor conductivity that the usual meanfield theory of superconductivity breaks down because of anomalously large classical and quantum fluctuations of the phase of the superconducting order parameter. It is argued that the supression of a first order phase transition (phase separation) by the long-range Coulomb interaction leads to high temperature superconductivity accompanied by static or dynamical charge inhomogeneIty. Evidence in support of this picture for high temperature superconductors is described.

  3. Superconductivity in doped insulators

    International Nuclear Information System (INIS)

    It is shown that many synthetic metals, including high temperature superconductors are ''bad metals'', with such a poor conductivity that the usual mean-field theory of superconductivity breaks down because of anomalously large classical and quantum fluctuations of the phase of the superconducting order parameter. It is argued that the supression of a first order phase transition (phase separation) by the long-range Coulomb interaction leads to high temperature superconductivity accompanied by static or dynamical charge inhomogeneity. Evidence in support of this picture for high temperature superconductors is described. (orig.)

  4. Laser hearth melt processing of ceramic materials

    Science.gov (United States)

    Richard Weber, J. K.; Felten, J. J.; Nordine, Paul C.

    1996-02-01

    A new technique for synthesizing small batches of oxide-based ceramic and glass materials from high purity powders is described. The method uses continuous wave CO2 laser beam heating of material held on a water-cooled copper hearth. Contamination which would normally result during crucible melting is eliminated. Details of the technique are presented, and its operation and use are illustrated by results obtained in melting experiments with a-aluminum oxide, Y-Ba-Cu-O superconductor material, and the mixtures, Al2O3-SiO2, Bi2O3-B2O3, Bi2O3-CuO. Specimen masses were 0.05-1.5 g.

  5. Thin film ceramic thermocouples

    Science.gov (United States)

    Gregory, Otto (Inventor); Fralick, Gustave (Inventor); Wrbanek, John (Inventor); You, Tao (Inventor)

    2011-01-01

    A thin film ceramic thermocouple (10) having two ceramic thermocouple (12, 14) that are in contact with each other in at least on point to form a junction, and wherein each element was prepared in a different oxygen/nitrogen/argon plasma. Since each element is prepared under different plasma conditions, they have different electrical conductivity and different charge carrier concentration. The thin film thermocouple (10) can be transparent. A versatile ceramic sensor system having an RTD heat flux sensor can be combined with a thermocouple and a strain sensor to yield a multifunctional ceramic sensor array. The transparent ceramic temperature sensor that could ultimately be used for calibration of optical sensors.

  6. Formation of texturised HTSC coatings of the Bi-system by thermal spraying methods

    International Nuclear Information System (INIS)

    In this work, we present results of investigations of the superconducting properties of the coatings of the BiSrCaCuO composition of a non-oriented substrates produced by the gas-detonation method in Dnepr-3 equipment, and also the effect of annealing on the properties of these materials

  7. Application of photo-thermal-stimulation exo-emission method for investigation of HTSC-ceramics on YBa2Cu3O7-δ

    International Nuclear Information System (INIS)

    The method of photothermostimulated exoelectron emission (PhTSE) is applied to study the processes running in subsurface layers of HTSC ceramics based on YBa2Cu3O7-δ. Correlations are revealed between variations of exoemission current value and superconducting transition. The point in time at which the specimen transforms into a superconducting state is reflected by a bend at the temperature dependence of PhTSE intensity. The results obtained are indicative of perspectiveness of further development of a PhTSE method as an electric one to determine a superconducting transition, to study its dynamics and associated processes at HTSC ceramics surfaces with temperature varying

  8. Photoinduced superconductivity in semiconductors

    Science.gov (United States)

    Goldstein, Garry; Aron, Camille; Chamon, Claudio

    2015-02-01

    We show that optically pumped semiconductors can exhibit superconductivity. We illustrate this phenomenon in the case of a two-band semiconductor tunnel-coupled to broad-band reservoirs and driven by a continuous wave laser. More realistically, we also show that superconductivity can be induced in a two-band semiconductor interacting with a broad-spectrum light source. We furthermore discuss the case of a three-band model in which the middle band replaces the broad-band reservoirs as the source of dissipation. In all three cases, we derive the simple conditions on the band structure, electron-electron interaction, and hybridization to the reservoirs that enable superconductivity. We compute the finite superconducting pairing and argue that the mechanism can be induced through both attractive and repulsive interactions and is robust to high temperatures.

  9. Magnetic and superconducting nanowires

    DEFF Research Database (Denmark)

    Piraux, L.; Encinas, A.; Vila, L.;

    2005-01-01

    magnetic and superconducting nanowires. Using different approaches entailing measurements on both single wires and arrays, numerous interesting physical properties have been identified in relation to the nanoscopic dimensions of these materials. Finally, various novel applications of the nanowires are also...

  10. Higher critical current density achieved in Bi-2223 High-Tc superconductors

    Directory of Open Access Journals (Sweden)

    M.S. Shalaby

    2016-07-01

    Full Text Available Bi2Sr2Ca2Cu3Ox (Bi-2223 were prepared using a solid state reaction method at different sintering times and temperatures. Structural phase identifications have been done using X-Ray analysis and refinement by Reitveld method which proves the coexistence of Bi-2223 and Bi-2212 phases. The critical transition temperature Tc and critical current density Jc values were measured using superconducting quantum interference device magnetometer (SQUID and by the magneto-optics technique. A remarkable rapid decrease to the diamagnetic signal in the magnetization versus temperature M(T at 110 K and Jc around 1.2 × 107 A/m2 at 5 K are confirmed for the Bi-2223 compound.

  11. Photoemission, Correlation and Superconductivity:

    Science.gov (United States)

    Abrecht, M.; Ariosa, D.; Cloëtta, D.; Pavuna, D.; Perfetti, L.; Grioni, M.; Margaritondo, G.

    We review some of the problems still affecting photoemission as a probe of high-temperature superconductivity, as well as important recent results concerning their solution. We show, in particular, some of the first important results on thin epitaxial films grown by laser ablation, which break the monopoly of cleaved BCSCO in this type of experiments. Such results, obtained on thin LSCO, may have general implications on the theory of high-temperature superconductivity.

  12. Relativistic Theory of Superconductivity

    OpenAIRE

    Capelle, K.; Marques, M. A. L.; Gross, E. K. U.

    2001-01-01

    The relativistic generalization of the theory of superconductivity is reviewed with respect to its conceptual basis and first applications. The construction of relativistically covariant order parameters for superconductors is outlined and the generalization of the Dirac equation for the superconducting state is presented. A weakly relativistic expansion of this equation leads to the Pauli equation for superconductors, which describes the lowest-order relativistic corrections to the conventio...

  13. Bi-based superconductor

    Directory of Open Access Journals (Sweden)

    S E Mousavi

    2009-08-01

    Full Text Available   In this paper, Bi-Sr-Ca-Cu-O (BCSCCO system superconductor is made by the solid state reaction method. The effect of doping Pb, Cd, Sb, Cu and annealing time on the critical temperature and critical current density have been investigated. The microstructure and morphology of the samples have been studied by X-ray diffraction, scanning electron microscope and energy dispersive X-ray. The results show that the fraction of Bi-2223 phase in the Bi- based superconductor, critical temperature and critical current density depend on the annealing temperature, annealing time and the kind and amount of doping .

  14. Superconducting Fullerene Nanowhiskers

    Directory of Open Access Journals (Sweden)

    Yoshihiko Takano

    2012-04-01

    Full Text Available We synthesized superconducting fullerene nanowhiskers (C60NWs by potassium (K intercalation. They showed large superconducting volume fractions, as high as 80%. The superconducting transition temperature at 17 K was independent of the K content (x in the range between 1.6 and 6.0 in K-doped C60 nanowhiskers (KxC60NWs, while the superconducting volume fractions changed with x. The highest shielding fraction of a full shielding volume was observed in the material of K3.3C60NW by heating at 200 °C. On the other hand, that of a K-doped fullerene (K-C60 crystal was less than 1%. We report the superconducting behaviors of our newly synthesized KxC60NWs in comparison to those of KxC60 crystals, which show superconductivity at 19 K in K3C60. The lattice structures are also discussed, based on the x-ray diffraction (XRD analyses.

  15. Electron pairing without superconductivity

    Science.gov (United States)

    Levy, Jeremy

    Strontium titanate (SrTiO3) is the first and best known superconducting semiconductor. It exhibits an extremely low carrier density threshold for superconductivity, and possesses a phase diagram similar to that of high-temperature superconductors--two factors that suggest an unconventional pairing mechanism. Despite sustained interest for 50 years, direct experimental insight into the nature of electron pairing in SrTiO3 has remained elusive. Here we perform transport experiments with nanowire-based single-electron transistors at the interface between SrTiO3 and a thin layer of lanthanum aluminate, LaAlO3. Electrostatic gating reveals a series of two-electron conductance resonances--paired electron states--that bifurcate above a critical pairing field Bp of about 1-4 tesla, an order of magnitude larger than the superconducting critical magnetic field. For magnetic fields below Bp, these resonances are insensitive to the applied magnetic field; for fields in excess of Bp, the resonances exhibit a linear Zeeman-like energy splitting. Electron pairing is stable at temperatures as high as 900 millikelvin, well above the superconducting transition temperature (about 300 millikelvin). These experiments demonstrate the existence of a robust electronic phase in which electrons pair without forming a superconducting state. Key experimental signatures are captured by a model involving an attractive Hubbard interaction that describes real-space electron pairing as a precursor to superconductivity. Support from AFOSR, ONR, ARO, NSF, DOE and NSSEFF is gratefully acknowledged.

  16. Comparative study of flexural strength test methods on CAD/CAM Y-TZP dental ceramics

    Science.gov (United States)

    Xu, Yongxiang; Han, Jianmin; Lin, Hong; An, Linan

    2015-01-01

    Clinically, fractures are the main cause of computer-aided design and computer-aided manufacturing (CAD/CAM) 3 mol%-yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) all-ceramic dental restorations failure because of repetitive occlusal loading. The goal of this work is to study the effect of test methods and specimen’s size on the flexural strength of five ceramic products. Both bi-axial flexure test (BI) and uni-axial flexure tests (UNI), including three-point flexure test (3PF) and four-point flexure test (4PF), are used in this study. For all five products, the flexural strength is as follows: BI > 3PF > 4PF. Furthermore, specimens with smaller size (3PF-s) have higher values than the bigger ones (3PF). The difference between BI and UNI resulted from the edge flaws in ceramic specimens. The relationship between different UNI (including 3PF-s, 3PF and 4PF) can be explained according to Weibull statistical fracture theory. BI is recommended to evaluate the flexural strength of CAD/CAM Y-TZP dental ceramics. PMID:26816646

  17. High Gain and High Directive of Antenna Arrays Utilizing Dielectric Layer on Bismuth Titanate Ceramics

    Directory of Open Access Journals (Sweden)

    F. H. Wee

    2012-01-01

    Full Text Available A high gain and high directive microstrip patch array antenna formed from dielectric layer stacked on bismuth titanate (BiT ceramics have been investigated, fabricated, and measured. The antennas are designed and constructed with a combination of two-, four-, and six-BiT elements in an array form application on microwave substrate. For gain and directivity enhancement, a layer of dielectric was stacked on the BiT antenna array. We measured the gain and directivity of BiT array antennas with and without the dielectric layer and found that the gain of BiT array antenna with the dielectric layer was enhanced by about 1.4 dBi of directivity and 1.3 dB of gain over the one without the dielectric layer at 2.3 GHz. The impedance bandwidth of the BiT array antenna both with and without the dielectric layer is about 500 MHz and 350 MHz, respectively, which is suitable for the application of the WiMAX 2.3 GHz system. The utilization of BiT ceramics that covers about 90% of antenna led to high radiation efficiency, and small-size antennas were produced. In order to validate the proposed design, theoretical and measured results are provided and discussed.

  18. Bi-Force

    DEFF Research Database (Denmark)

    Sun, Peng; Speicher, Nora K; Röttger, Richard;

    2014-01-01

    datasets from Gene Expression Omnibus were analyzed. All resulting biclusters were subsequently investigated by Gene Ontology enrichment analysis to evaluate their biological relevance. The distinct theoretical foundation of Bi-Force (bicluster editing) is more powerful than strict biclustering. We thus......-clustering', has been successfully utilized to discover local patterns in gene expression data and similar biomedical data types. Here, we contribute a new heuristic: 'Bi-Force'. It is based on the weighted bicluster editing model, to perform biclustering on arbitrary sets of biological entities, given any kind...... comparative analysis of biclustering algorithms for gene expressiondata. Brief. Bioinform., 14:279-292.) and compared Bi-Force against eight existing tools: FABIA, QUBIC, Cheng and Church, Plaid, BiMax, Spectral, xMOTIFs and ISA. To this end, a suite of synthetic datasets as well as nine large gene expression...

  19. Superconducting transition in ruthenocuprate RuSr2GdCu2O8 viewed from the studies of the imaginary part of ac susceptibility

    Science.gov (United States)

    Zivkovic, I.; Drobac, D.; Ariosa, D.; Berger, H.; Pavuna, D.; Prester, M.

    2002-12-01

    We have measured two structurally similar superconducting systems, RuSr2GdCu2O8 and GdBa2Cu3O7 by means of high-resolution ac susceptibility. The real and the imaginary part of ac susceptibility of both bulk-ceramic and powdered samples have been studied down to the very small magnetic-field levels. We show that there are significant differences in the evolution of superconductivity in the two studied superconducting systems. In particular, we show that the superconducting transition in the grains in RuSr2GdCu2O8 system is masked with intrinsic magnetism of complex origin.

  20. Effect of neutron irradiation on Tc of Pb-doped BiSrCaCuO superconductor

    Science.gov (United States)

    Herr, Young-Hoi; Lee, Kwang-Hee; Kim, Chan-Joong; Lee, Hee-Gyoun; Kim, Chun-Taik

    1989-09-01

    A Pb-doped BiSrCaCuO superconductor was irradiated in a TRIGA MARK III reactor up to a neutron fluence of 7.6 x 10 to the 17th n/sq cm. The measured superconducting transition temperature (Tc) after irradiation was decreased to 92.5 K from nonirradiated data of 102 K. The fractional decrease of the Tc was compared with results for other superconducting materials. Some recovery of irradiation-induced Tc decrease was observed.

  1. Bonding of a silver sheath on textured-powder ribbons of green-state Bi-2212 superconductor

    Science.gov (United States)

    Smit, Klaus; McIntyre, Peter; Damborsky, Kyle; Lu, Feng; Pogue, Nathaniel

    2011-10-01

    A novel method is being developed for fabrication of textured-powder jelly-roll (TPJR) Bi-2212/Ag superconducting wire for applications in high-field magnets. In this process two silver foils must be fused together to enclose a ribbon of compacted, textured Bi-2212 fine powder. Fusing the silver foils must be accomplished with minimum heating of the superconducting powder filling. We are investigating methods using cold-welding, ultrasonic welding, and laser welding. Results of those investigations will be reported.

  2. Recent Advances in Layered Metal Chalcogenides as Superconductors and Thermoelectric Materials: Fe-Based and Bi-Based Chalcogenides.

    Science.gov (United States)

    Mizuguchi, Yoshikazu

    2016-04-01

    Recent advances in layered (Fe-based and Bi-based) chalcogenides as superconductors or functional materials are reviewed. The Fe-chalcogenide (FeCh) family are the simplest Fe-based high-Tc superconductors. The superconductivity in the FeCh family is sensitive to external or chemical pressure, and high Tc is attained when the local structure (anion height) is optimized. The Bi-chalcogenide (BiCh2 ) family are a new group of layered superconductors with a wide variety of stacking structures. Their physical properties are also sensitive to external or chemical pressure. Recently, we revealed that the emergence of superconductivity and the Tc in this family correlate with the in-plane chemical pressure. Since the flexibility of crystal structure and electronic states are an advantage of the BiCh2 family for designing functionalities, I briefly review recent developments in this family as not only superconductors but also other functional materials. PMID:26821763

  3. Macroscopic Models of Superconductivity

    Science.gov (United States)

    Chapman, S. J.

    Available from UMI in association with The British Library. Requires signed TDF. After giving a description of the basic physical phenomena to be modelled, we begin by formulating a sharp -interface free-boundary model for the destruction of superconductivity by an applied magnetic field, under isothermal and anisothermal conditions, which takes the form of a vectorial Stefan model similar to the classical scalar Stefan model of solid/liquid phase transitions and identical in certain two-dimensional situations. This model is found sometimes to have instabilities similar to those of the classical Stefan model. We then describe the Ginzburg-Landau theory of superconductivity, in which the sharp interface is 'smoothed out' by the introduction of an order parameter, representing the number density of superconducting electrons. By performing a formal asymptotic analysis of this model as various parameters in it tend to zero we find that the leading order solution does indeed satisfy the vectorial Stefan model. However, at the next order we find the emergence of terms analogous to those of 'surface tension' and 'kinetic undercooling' in the scalar Stefan model. Moreover, the 'surface energy' of a normal/superconducting interface is found to take both positive and negative values, defining Type I and Type II superconductors respectively. We discuss the response of superconductors to external influences by considering the nucleation of superconductivity with decreasing magnetic field and with decreasing temperature respectively, and find there to be a pitchfork bifurcation to a superconducting state which is subcritical for Type I superconductors and supercritical for Type II superconductors. We also examine the effects of boundaries on the nucleation field, and describe in more detail the nature of the superconducting solution in Type II superconductors--the so-called 'mixed state'. Finally, we present some open questions concerning both the modelling and analysis of

  4. Ceramic tamper-revealing seals

    Science.gov (United States)

    Kupperman, David S.; Raptis, Apostolos C.; Sheen, Shuh-Haw

    1992-01-01

    A flexible metal or ceramic cable with composite ceramic ends, or a u-shaped ceramic connecting element attached to a binding element plate or block cast from alumina or zirconium, and connected to the connecting element by shrink fitting.

  5. Analyses of fine paste ceramics

    International Nuclear Information System (INIS)

    Four chapters are included: history of Brookhaven fine paste ceramics project, chemical and mathematical procedures employed in Mayan fine paste ceramics project, and compositional and archaeological perspectives on the Mayan fine paste ceramics

  6. Analyses of fine paste ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Sabloff, J A [ed.

    1980-01-01

    Four chapters are included: history of Brookhaven fine paste ceramics project, chemical and mathematical procedures employed in Mayan fine paste ceramics project, and compositional and archaeological perspectives on the Mayan fine paste ceramics. (DLC)

  7. Continuous Fiber Ceramic Composites

    Energy Technology Data Exchange (ETDEWEB)

    None

    2002-09-01

    Fiber-reinforced ceramic composites demonstrate the high-temperature stability of ceramics--with an increased fracture toughness resulting from the fiber reinforcement of the composite. The material optimization performed under the continuous fiber ceramic composites (CFCC) included a series of systematic optimizations. The overall goals were to define the processing window, to increase the robustinous of the process, to increase process yield while reducing costs, and to define the complexity of parts that could be fabricated.

  8. Measuring Fracture Times Of Ceramics

    Science.gov (United States)

    Shlichta, Paul J.; Bister, Leo; Bickler, Donald G.

    1989-01-01

    Electrical measurements complement or replace fast cinematography. Electronic system measures microsecond time intervals between impacts of projectiles on ceramic tiles and fracture tiles. Used in research on ceramics and ceramic-based composite materials such as armor. Hardness and low density of ceramics enable them to disintegrate projectiles more efficiently than metals. Projectile approaches ceramic tile specimen. Penetrating foil squares of triggering device activate display and recording instruments. As ceramic and resistive film break oscilloscope plots increase in electrical resistance of film.

  9. Superconductivity for hydrogen economy

    International Nuclear Information System (INIS)

    The emerging hydrogen economy is expected to deal with a large amount of liquid hydrogen produced from the renewable energy resources. The main advantage of liquid hydrogen in comparison with other forms of its storage and transportation is in allowing wide use of superconductivity, which would optimise energy efficiency of the economy. The basic element of the infrastructure for hydrogen economy is a network of superconducting pipelines carrying simultaneously liquid hydrogen and loss-free electricity. The most likely material for such infrastructure is MgB2, the only superconductor efficiently working at boiling temperature of liquid hydrogen and not showing strong critical current reduction on grain boundaries. The cheap techniques for the preparation of MgB2 are hot isostatic pressing, resistive sintering and paint coating. These and other advanced techniques are able to provide MgB2 with suitable for the infrastructure structural and superconducting properties. The preparation of a large-area superconducting joint between two pieces of MgB2 as a technique enabling this infrastructure is reported. A potential of synergy between liquid hydrogen and superconductivity is revealed in a range of possible new energy applications.

  10. Superconductivity and macroscopic quantum phenomena

    International Nuclear Information System (INIS)

    It is often asserted that superconducting systems are manifestations of quantum mechanics on a macroscopic scale. In this review article it is demonstrated that this quantum assertion is true within the framework of the microscopic theory of superconductivity. (Auth.)

  11. Defect production in ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Zinkle, S.J. [Oak Ridge National Lab., TN (United States); Kinoshita, C. [Kyushu Univ. (Japan)

    1997-08-01

    A review is given of several important defect production and accumulation parameters for irradiated ceramics. Materials covered in this review include alumina, magnesia, spinel silicon carbide, silicon nitride, aluminum nitride and diamond. Whereas threshold displacement energies for many ceramics are known within a reasonable level of uncertainty (with notable exceptions being AIN and Si{sub 3}N{sub 4}), relatively little information exists on the equally important parameters of surviving defect fraction (defect production efficiency) and point defect migration energies for most ceramics. Very little fundamental displacement damage information is available for nitride ceramics. The role of subthreshold irradiation on defect migration and microstructural evolution is also briefly discussed.

  12. Dielectric and Piezoelectric Properties of Sodium Bismuth Titanate Ceramics with KCe Substitution

    Institute of Scientific and Technical Information of China (English)

    XU Jian-Xiu; ZHAO Liang; ZHANG Cheng-Ju

    2008-01-01

    @@ The piezoelectric properties of the (KCe)-substituted sodium bismuth titanate (Na0.5Bi4.5 Ti4O15, NBT) piezo-electric ceramics are investigated. The piezoelectric properties of NBT ceramics are significantly enhanced by (KCe) substitution. The Curie temperature Tc, and piezoelectric coefficient d33 for the (KCe)-substituted NBT are found to be 663°C, and 27pC/N, respectively. Dielectric and annealing spectroscopy present that the (KCe) co-substituted NBT piezoelectric ceramics possess stable piezoelectric properties.

  13. Large electrostrictive effect and bright upconversion luminescence in Er-modified 0.92(Bi{sub 0.5}Na{sub 0.5})TiO{sub 3}–0.08(Ba{sub 0.90}Ca{sub 0.10})(Ti{sub 0.92}Sn{sub 0.08})O{sub 3} lead-free ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiaoli; Wu, Meihua; Diao, Wenxin; Zhang, Bing; Hao, Jigong, E-mail: haojigong@lcu.edu.cn; Xu, Zhijun; Chu, Ruiqing

    2015-10-01

    In this study, a new lead-free luminescent electrostrictive material has been obtained by introducing trivalent Er{sup 3+} as the activator into 0.92(Bi{sub 0.5}Na{sub 0.5})TiO{sub 3}–0.08(Ba{sub 0.90}Ca{sub 0.10})(Ti{sub 0.92}Sn{sub 0.08})O{sub 3} (BNT–0.08BCST). A high, purely electrostrictive effect (the electrostrictive coefficient Q{sub 33} reaches up to 0.028 m{sup 4}/C{sup 2}) with exceptionally good fatigue resistance (up to 10{sup 6} cycles) and thermostability (25–140 °C) is obtained in 0.2 mol%Er-modified BNT–0.08BCST ceramics. Besides the excellent electrostrictive properties, Er{sup 3+}-modified BNT–0.08BCST samples exhibit a strong green-red upconversion emission, and the emission intensities are strongly dependent on the doping concentration, which reaches the optimal value as the doping concentration is 0.4 mol%. These results suggest that this kind of material may have potential application as a multifunctional device by integrating its excellent upconversion luminescence and electrostrictive properties.

  14. Nanoscience and Engineering in Superconductivity

    CERN Document Server

    Moshchalkov, Victor; Lang, Wolfgang

    2010-01-01

    For emerging energy saving technologies, superconducting materials with superior performance are needed. Such materials can be developed by manipulating the 'elementary building blocks' through nanostructuring. For superconductivity the 'elementary blocks' are Cooper pair and fluxon (vortex). This book presents new ways how to modify superconductivity and vortex matter through nanostructuring and the use of nanoscale magnetic templates. The basic nano-effects, vortex and vortex-antivortex patterns, vortex dynamics, Josephson phenomena, critical currents, and interplay between superconductivity

  15. Superconducting accelerator magnet design

    International Nuclear Information System (INIS)

    Superconducting dipoles, quadrupoles and correction magnets are necessary to achieve the high magnetic fields required for big accelerators presently in construction or in the design phase. Different designs of superconducting accelerator magnets are described and the designs chosen at the big accelerator laboratories are presented. The most frequently used cosθ coil configuration is discussed in detail. Approaches for calculating the magnetic field quality including coil end fields are presented. Design details of the cables, coils, mechanical structures, yokes, helium vessels and cryostats including thermal radiation shields and support structures used in superconducting magnets are given. Necessary material properties are mentioned. Finally, the main results of magnetic field measurements and quench statistics are presented. (orig.)

  16. Applied Superconductivity Conference 2014

    CERN Document Server

    2015-01-01

    Energy Efficiency is a worldwide imperative driven by an increasing awareness of the need to conserve valuable natural resources. Superconductivity, the technology which revolutionized non-invasive medical imaging through MRI starting in the 1980’s, is one of the most promising enablers of energy efficiency in the 21st century. From energy efficient supercomputers to power generation, transmission, and storage, the spectrum of applications of superconductivity is broad in its reach and potential. As ASC comes to Charlotte, site of the hall of fame of NASCAR, our theme, “Race to Energy Efficiency,” is intended to inspire the world experts in superconductivity who will converge to Charlotte to present their latest results, exchange information, network, and plan and project the future breakthroughs.

  17. Connectivity and superconductivity

    CERN Document Server

    Rubinstein, Jacob

    2000-01-01

    The motto of connectivity and superconductivity is that the solutions of the Ginzburg--Landau equations are qualitatively influenced by the topology of the boundaries, as in multiply-connected samples. Special attention is paid to the "zero set", the set of the positions (also known as "quantum vortices") where the order parameter vanishes. The effects considered here usually become important in the regime where the coherence length is of the order of the dimensions of the sample. It takes the intuition of physicists and the awareness of mathematicians to find these new effects. In connectivity and superconductivity, theoretical and experimental physicists are brought together with pure and applied mathematicians to review these surprising results. This volume is intended to serve as a reference book for graduate students and researchers in physics or mathematics interested in superconductivity, or in the Schrödinger equation as a limiting case of the Ginzburg--Landau equations.

  18. Superconducting super collider

    International Nuclear Information System (INIS)

    The Superconducting Super Collider is to be a 20 TeV per beam proton-proton accelerator and collider. Physically the SCC will be 52 miles in circumference and slightly oval in shape. The use of superconducting magnets instead of conventional cuts the circumference from 180 miles to the 52 miles. The operating cost of the SCC per year is estimated to be about $200-250 million. A detailed cost estimate of the project is roughly $3 billion in 1986 dollars. For the big collider ring, the technical cost are dominated by the magnet system. That is why one must focus on the cost and design of the magnets. Presently, the process of site selection is underway. The major R and D efforts concern superconducting dipoles. The magnets use niobium-titanium as a conductor stabilized in a copper matrix. 10 figures

  19. Superconductivity at Any Temperature

    CERN Document Server

    Anber, Mohamed M; Sabancilar, Eray; Shaposhnikov, Mikhail

    2016-01-01

    We construct a 2+1 dimensional model that sustains superconductivity at all temperatures. This is achieved by introducing a Chern Simons mixing term between two Abelian gauge fields A and Z. The superfluid is described by a complex scalar charged under Z, whereas a sufficiently strong magnetic field of A forces the superconducting condensate to form at all temperatures. In fact, at finite temperature, the theory exhibits Berezinsky-Kosterlitz-Thouless phase transition due to proliferation of topological vortices admitted by our construction. However, the critical temperature is proportional to the magnetic field of A, and thus, the phase transition can be postponed to high temperatures by increasing the strength of the magnetic field. This model can be a step towards realizing the long sought room temperature superconductivity.

  20. Study on BaO-Sm2O3-TiO2 Microwave Dielectric Ceramics Doped with Bismuth and Zinc

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    BaO-Sm2O3-TiO2 microwave dielectric ceramics doped with Bi and Zn was studied. The experiment was based on BST microwave dielectric ceramics doped with Bi2O3, which is shown by Ba4(Sm1-yBiy)28/3Ti18O54. When y=0.15, ZnO was added and the effects of ZnO on this system were studied. The result shows that the dielectric characteristics of BST microwave dielectric ceramics are the most excellent when the content of ZnO is 3%, and the optimal sintering temperature is 1200 ℃.