WorldWideScience

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. Study on mechanical properties in superconducting ceramics based on Bi-Sr-Ca-Cu-O doped with lead

    International Nuclear Information System (INIS)

    Investigations performed in superconducting ceramics based on Bi-Sr-Ca-Cu-O, doped with lead, according to the stoichiometric formulae Bi2-x Pbx SR2 Ca2 Cu3 Oy, demonstrated the insertion of lead alters the mechanical properties of the material,particularly the plasticity. When employing an Hardness Testing, it was observed that the sample with a lead concentration of x = 0.4 holds the highest Vickers microhardness. It was laos noticed, when using a mercury porosimeter, that on this concentration there was a drastic reduction of the volume of each pore, evincing the lead enhanced the sintering process, considering that the sample with a lead concentration of x = 0.4 holds the minimum interval in which 80% of the pores meet (0.19 a 0.79 μm). Through optical and electronic microscopy, one can notice the presence of two main phases: a phase presenting isolating properties and another with superconducting ones. A minor phase, with birefringent properties, was also observed showing its highest concentration in the sample x = 0.2. The increase in microhardness, reaching its top in sample x = 0.4, is due to the volume reduction of the phase with isolating properties (with a lower hardness, as it was observed in the polishing), for it reaches its minimum in the sample presenting the same concentration. Also through electronic microscopy, it was noted the highest microhardness in the sample x = 0.4 was not influenced by the diameter variance or by the crystal shape, since they all present the shape of lamelars plates. Chemical etching based on acetic acid and water, have been performed in order to verify the solubility of the present phases. It was observed that the phase showing birefringent properties were much more soluble than the others. It was also observed the features of sheet, product of the reaction between the acid and the sample, on the surfaces of the samples. The diameter of these decreased until the moment when in lead concentration x = 0.1 there was no more

  4. 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.

  5. 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

  6. 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

  7. 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)

  8. 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

  9. Glass-Derived Superconductive Ceramic

    Science.gov (United States)

    Bansal, Narottam P.; Farrell, D. E.

    1992-01-01

    Critical superconducting-transition temperature of 107.2 K observed in specimen made by annealing glass of composition Bi1.5Pb0.5Sr2Ca2Cu3Ox for 243 h at 840 degrees C. PbO found to lower melting temperature and viscosity of glass, possibly by acting as fluxing agent. Suggested partial substitution of lead into bismuth oxide planes of crystalline phase having Tc of 110 K stabilizes this phase and facilitates formation of it.

  10. Manufacturing of superconductive silver/ceramic composites

    DEFF Research Database (Denmark)

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

    2000-01-01

    . After the mechanical deformation the tapes are heat treated at approximately 835C whereby the powder-cores by phase diffusion and grain growth are converted into superconducting, ceramic fibres. The geometry, density and texture of the powder cores before heat treatment is essential for the quality and......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...

  11. Superconductive percolation in Bi-based superconductor/Bi-based insulator composites: case of Bi-2223/Bi-2310 and Bi-2212/BiFeO3

    International Nuclear Information System (INIS)

    Preparation of Bi-2223/Bi-2310 and Bi-2212/BiFeO3 composites has been performed so as to obtain some active composites where the superconductive properties of Bi-2223 or Bi-2212 can be modified using a property of the insulating phase. In both cases superconductive percolation was obtained, but only in the case of a Bi-2223 (or Bi-2212)/Bi-2310 composite was no (or very weak) chemical reaction observed during sintering. Since the superconductive percolation threshold was obtained in this case for a concentration of Bi-2223 or Bi-2212 lower than 20%, a special composite model had to be considered. The Bi-2212/BiFeO3 system is very interesting due to the ferroic properties of BiFeO3. Superconductive percolation was achieved with this mixture too, but with more difficulties because of a chemical reaction occurring between the two compounds during sintering. A study of the properties of these composites has been performed and will be briefly described in what follows. The good quality of the Bi-2223 (or Bi-2212)/Bi-2310 composite enables us to expect some future applications. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

    Noudem, J.G.

    1995-10-27

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

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

    Indian Academy of Sciences (India)

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

    2005-02-01

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

  14. 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)

  15. Electrical resistivity measurements in superconducting ceramics

    International Nuclear Information System (INIS)

    Electrical resistivity measurements have been done in (Y,Ba,Cu,O)- and (Y,Al,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)

  16. Superconductive ceramics obtained with sol gel method

    International Nuclear Information System (INIS)

    Several sol gel routes have been considered, studied and developed to produce large quantities of granulates which can be processed to obtain ceramics having good superconducting characteristics. In the considered process a mixture of commercial nitrates is atomized, at room temperature, in a solution 1:1 of Primene JMT and Benzene and a pale blue gel of the starting elements is suddently formed. The granulates obtained are free flowing, very reactive and well suited for pressing. For their intrinsic characteristics they could be very good precursors for the production of large quantities of superconductive ceramics in different forms. The precipitated gel is dried, calcinated, pressed in the form of cylindrical pellets which are sintered up to 960 degrees C. No griding or different thermal treatments are needed. The sintered material has low electric resistence, shows a clear Meissner effect and has a transition temperature of between 91 and 95 K

  17. 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.

  18. Observation of superconductivity in single crystalline Bi nanowires

    International Nuclear Information System (INIS)

    Bi nanowires have been fabricated by electrochemical deposition into the pores of ion track etched polycarbonate membranes. Transmission electron microscopy and selected area electron diffraction measurements reveal that these Bi nanowires are single crystalline with the rhombohedral lattice structure of bulk Bi at ambient pressure. We have measured the temperature dependence of the resistance and I-V characteristics at various magnetic fields on these Bi nanowires. These measurements show clear evidence for superconductivity below 0.64 K

  19. The influence of urea on the formation process of BiPbSrCaCuO superconducting ceramics synthesized by spray pyrolysis method

    International Nuclear Information System (INIS)

    The influence of urea on the formation process in the Bi-Pb-Sr-Ca-Cu-O system, as well as, on the final high Tc phase content and morphology of the powders obtained by spray pyrolysis method was studied. The process involves aerosol formation from common nitrate solutions (with and without urea addition) using ultrasonic atomizer operated at 1.7 MHz and control over aerosol decomposition up to 840 C. It was shown that the presence of urea in the precursor solutions promotes a faster phase transformation, improves homogeneity, reduces substantially the mean particle size and affects the resulting morphology of powders. (orig.)

  20. Bismuthates: BaBiO3 and related superconducting phases

    International Nuclear Information System (INIS)

    Highlights: • BaBiO3 has the perovskite structure, but tilting of the BiO6 octahedra destroy the ideal cubic symmetry except at temperatures above 820 K. BaBiO3 is a diamagnetic semiconductor due to a CDW, which is equivalent to a Ba2Bi3+Bi5+O6 representation. • Recent calculations and experimental results confirm that there is no significant deviation from the oxidation states of 3+ and 5+. • Superconductivity with a Tc as high as 13 K occurs for BaPb1−xBixO3 phases where the 6s band is about 25% filled, and superconductivity with a Tc as high as 34 K occurs for Ba1−xKxBiO3 phases where the 6s band is about 35% filled. • These two solid solutions can have cubic, tetragonal, or orthorhombic symmetry. • However, superconductivity has only been observed when the symmetry is tetragonal. - Abstract: BaBiO3 has the perovskite structure, but tilting of the BiO6 octahedra destroy the ideal cubic symmetry except at temperatures above 820 K. BaBiO3 is a diamagnetic semiconductor due to a charge density wave (CDW), which is equivalent to a Ba2Bi3+Bi5+O6 representation. Recent calculations and experimental results confirm that there is no significant deviation from the oxidation states of 3+ and 5+. Superconductivity with a Tc as high as 13 K occurs for BaPb1−xBixO3 phases where the 6s band is about 25% filled, and superconductivity with a Tc as high as 34 K occurs for Ba1−xKxBiO3 phases where the 6s band is about 35% filled. Structures in these two solid solutions can have cubic, tetragonal, orthorhombic, or monoclinic symmetry. However, superconductivity has only been observed when the symmetry is tetragonal

  1. Phase structure and properties of superconducting ceramics on a bases of Bi1,7Pb0,3Sr2Ca2Cu3Oy precursors received by melt rapid quenching on the solar furnace

    International Nuclear Information System (INIS)

    Full text: Formation of the superconductor ceramics on the base of precursors of nominal composition Bi1,7Pb0,3Sr2Ca2Cu3Oy, synthesized in solar furnace by melt rapid quenching method was studied. Phase composition of the samples by microstructure and X-ray analysis was investigated. Simultaneously warm-up dependencies of the electric resistance and magnetic receptivity are determined. Influence of composition and crystalline structure of a substrates on texture of a superconductor ceramics was studied. Considerable role of a melt quenching condition and insignificant role of a substrates type were observed. (authors)

  2. 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.

  3. In situ strain measurements of Bi2223 superconducting filaments in multifilamentary Ag-sheathed Bi2223 superconducting tapes

    International Nuclear Information System (INIS)

    In situ strain measurement was made for Bi2223 superconducting filaments in Ag-sheathed Bi2223 composite tapes utilizing synchrotron radiation. The residual strain was 0.05 ± 0.01% in compression. A small deviation from linear relationship between strain of the Bi2223 filaments and the average strain of the sample was found, meaning a decrease in elastic modulus of the filament even below the irreversible strain

  4. 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

  5. Fabrication of joint Bi-2223/Ag superconducting tapes with BSCCO superconducting powders by diffusion bonding

    International Nuclear Information System (INIS)

    61-Filaments Bi-2223/Ag superconducting tapes have been successfully joined with BSCCO superconducting powder interlayer by diffusion bonding. The electrical properties of the diffusion bonding joints were tested by standard four probe method and the microstructures of the joints were also examined by SEM. Additionally, the phase constituents of the superconducting powders between the tapes before and after bonding process were evaluated by XRD analysis. The result shows that the diffusion bonding joints are superconductive. The microstructures of the joint display a good bonding with no cracks and discontinuities. The joining zones are mainly composed of Bi-2223 phase, Bi-2212 phase and a small amount of CuO, Ca2PbO4. At last, the phase transformations of the superconducting powders in the bonding process are discussed.

  6. Fabrication of joint Bi-2223/Ag superconducting tapes with BSCCO superconducting powders by diffusion bonding

    Science.gov (United States)

    Guo, Wei; Zou, Guisheng; Wu, Aiping; Zhou, Fangbing; Ren, Jialie

    2010-05-01

    61-Filaments Bi-2223/Ag superconducting tapes have been successfully joined with BSCCO superconducting powder interlayer by diffusion bonding. The electrical properties of the diffusion bonding joints were tested by standard four probe method and the microstructures of the joints were also examined by SEM. Additionally, the phase constituents of the superconducting powders between the tapes before and after bonding process were evaluated by XRD analysis. The result shows that the diffusion bonding joints are superconductive. The microstructures of the joint display a good bonding with no cracks and discontinuities. The joining zones are mainly composed of Bi-2223 phase, Bi-2212 phase and a small amount of CuO, Ca 2PbO 4. At last, the phase transformations of the superconducting powders in the bonding process are discussed.

  7. 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

  8. Unconventional Superconductivity in YPtBi and Related Topological Semimetals

    Science.gov (United States)

    Meinert, Markus

    2016-04-01

    YPtBi, a topological semimetal with a very low carrier density, was recently found to be superconducting below Tc=0.77 K . In conventional theory, the nearly vanishing density of states around the Fermi level would imply a vanishing electron-phonon coupling and would, therefore, not allow for superconductivity. Based on relativistic density-functional theory calculations of the electron-phonon coupling in YPtBi, it is found that carrier concentrations of more than 1021 cm-3 are required to explain the observed critical temperature with the conventional pairing mechanism, which is several orders of magnitude larger than experimentally observed. It is very likely that an unconventional pairing mechanism is responsible for the superconductivity in YPtBi and related topological semimetals with half-Heusler structure.

  9. Unconventional Superconductivity in YPtBi and Related Topological Semimetals.

    Science.gov (United States)

    Meinert, Markus

    2016-04-01

    YPtBi, a topological semimetal with a very low carrier density, was recently found to be superconducting below T_{c}=0.77  K. In conventional theory, the nearly vanishing density of states around the Fermi level would imply a vanishing electron-phonon coupling and would, therefore, not allow for superconductivity. Based on relativistic density-functional theory calculations of the electron-phonon coupling in YPtBi, it is found that carrier concentrations of more than 10^{21}  cm^{-3} are required to explain the observed critical temperature with the conventional pairing mechanism, which is several orders of magnitude larger than experimentally observed. It is very likely that an unconventional pairing mechanism is responsible for the superconductivity in YPtBi and related topological semimetals with half-Heusler structure. PMID:27081999

  10. Studies of two-powders mixtures in Bi(Pb)-Sr(Ba)-Ca-Cu- oxide/nitrate system obtained by freeze drying used for synthesis of 2223 superconducting ceramic

    International Nuclear Information System (INIS)

    Nitrate freeze dried raw powders Bi:Pb:Sr:Ba:Ca:Cu 1.8:0.4:1.8:0.2:2.2:3.0('2223-nitrate'). Bi:Pb:Sr:Ba:Ca:Cu 1.8:0.4:1.8:0.2:1.2:2.0 ('2212-nitrate') and Ca:Cu = 1:1 ('11-nitrate') have been decomposed at 840 deg. C for 30 min. to obtain '2223-oxide', '2212-oxide' and '11-oxide' powders. From the above powders the following mixtures (mechanically mixed) were prepared: '2212-oxide' + '11-nitrate', '2212-nitrate' + '11-oxide' and '2212-nitrate' + '11-nitrate' and thermally decomposed in the same conditions. The decomposed powders were investigated by XRD analysis. From the indicated decomposed mixtures, '2223-oxide' powder and mixture '2212-oxide' + '11-oxide' superconducting pellets with composition 2223 were sintered. Electrical resistance R(T) measurements on pellets have been performed. The obtained data have shown different phase compositions in the decomposed samples indicating different phase formation reactions. Because of this fact superconducting parameters in sintered pellets are changing. The optimum precursor powder considering R(T) results for the synthesis of 2223 phase is the decomposed sample '2212-nitrate + 11-nitrate', although the best level of mixing is in the '2223-oxide' powder. The most unfavorable mixture for 2212 and 2223-phase formation is the decomposed sample '2212-nitrate + 11-oxide' due to the lack of (Sr,Ca)CuO2 phase. (authors)

  11. Vibronic Jahn-Teller coupling and structural-systematic aspects of superconductivity in ceramic materials

    International Nuclear Information System (INIS)

    The following subjects were mainly investigated: 1. Development of a concept concerning the mechanism of superconductivity in ceramic oxides from the standpoint of solid state chemistry. An important criterion for generating superconductivity in ceramic oxides seems to be the overlap of a narrow, weakly antibonding and metal-centred band with a very broad band of predominant oxygen character in the Fermi region. Spectroscopic investigations are in favour of such a concept and additionally indicate a vibronic coupling mechanism of the Jahn-Teller- or pseudo-Jahn-Teller type. 2. Synthesis of potentially superconducting ceramic oxides. A series of oxidic compounds with transition metal ions (Ni2+/Ni3+/Ni4+, Mn3+/Mn4+, Cu2+/Cu3+ etc.) and with cations, possessing a lone electron pair (Sb3+, Bi3+, Pb2+, Tl+) was prepared (K2NiF4-structure). The investigation of these ceramic materials led to interesting insight into the nature of the M-O-bond and the cooperative interactions between the metal ion centres; new superconductors could not be synthesized, however. (orig.)

  12. Exoemission during phase transformations in superconducting monocrystal Bi2Sr2CaCu2Ox

    International Nuclear Information System (INIS)

    Low-temperature exoemission from a superconducting Bi2Sr2CaCu2Ox monocrystal under thermal cycling within 77-300 K interval is investigated. During thermal compression under cooling and subsequent expansion under heating, emission current peaks near 80 K and within the temperature intervals of structural phase transitions (SPT) (130-160, 180-200 and 240-280 K) are detected. Based on comparing the results to the earlier obtained ones for polycrystalline Y-Ba-Cu-O ceramics a conclusion is made that electron processes conductioning exoemission at SPT occur in the cuprate layer of HTSC

  13. 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)

  14. 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...

  15. 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

  16. Phonon Vibrations and Superconductivity of a Bi-based Superconductor

    Science.gov (United States)

    Lee, Jooseop; Stone, Matthew; Yildrim, Taner; Huq, Ashfia; Ehlers, Georg; Mizuguchi, Yoshikazu; Lee, Seunghun; University of Virginia Team; Oak Ridge National Laboratory Team; NIST CenterNeutron Research Team; Tokyo Metropolitan University Team

    2013-03-01

    Elastic and Inelastic neutron scattering experiments have been carried out on polycrystalline samples of the newly discovered layered superconductor LaO0.5F0.5BiS2, and its nonsuperconducting parent compound LaOBiS2 to determine their crystal structures and lattice vibrational modes. The Bragg peaks from the superconducting sample shows large broadening in width in the powder diffraction pattern. For the lattice vibrations, significant difference was observed upon F doping. Using the density functional perturbation theory, we identified all phonon modes, and show the major change in the phonon spectrum comes mainly from the change in the Oxygen mode. Even though strong electron phonon coupling constant was estimated, no significant difference in the phonon spectrum from BiS2 superconducting layer was found above and below Tc.

  17. Superconducting Gap and Pseudogap in Bi-2212

    OpenAIRE

    Opel, Matthias; Venturini, Francesca; Hackl, Rudi; Berger, Helmuth; Forro, Laszlo

    1999-01-01

    We present results of Raman scattering experiments in differently doped Bi-2212 single crystals. Below Tc the spectra show pair-breaking features in the whole doping range. The low frequency power laws confirm the existence of a $d_{x^2-y^2}$-wave order parameter. In the normal state between Tc and T* = 200K we find evidence for a pseudogap in B2g symmetry. Upon doping its effect on the spectra decreases while its energy scale appears to be unchanged.

  18. Dielectric investigations of BiFeO3 ceramics

    Directory of Open Access Journals (Sweden)

    Simonas Greičius

    2009-06-01

    Full Text Available In this paper we present the results from the investigation of the dielectric permittivity of BiFeO3 ceramics, prepared by mechanochemical synthesis method in a broad frequency and temperature range. The dielectric permittivity is mainly caused by high conductivity, which is suppressed in the frequencies above 1 MHz. The investigated ceramics showed conductivity activation energy E/k=11280±12 K, and σ0=54161±800 S. The plots of M* revealed conductivity mechanism with τ0=1.12·10^-13 s, and E/k=9245 K.

  19. Effects of Cr, Ta and Pb Substitutions on Phase Formation and Superconductivity of Tl1212 Ceramics

    Directory of Open Access Journals (Sweden)

    A.K. Yahya

    2008-01-01

    Full Text Available Effects of Cr, Ta and Pb substitutions for Sr/Tl on phase formation and superconductivity of Tl0.8 Bi0.2 Sr2-x CrxC a0.9Y0.1Cu2O7, Tl0.9Bi0.1Sr2-yTayCa0.9Y0.1Cu2O7 and Tl1-zPbzSr1.8Sb0.2CaCu2O7 ceramics were investigated. Powder X-ray diffraction patterns for the three series showed major 1212 phase with 1201 phase as the minor phase. Electrical (dc resistance measurements showed that the elemental substitutions at Sr site for Tl0.8Bi0.2Sr2-xCrxCa0.9Y0.1Cu2O7, (x = 0-0.3 and Tl0.9Bi0.1Sr2-yTayCa0.9Y0.1Cu2O7 (y = 0-0.3 series induced metal-insulator transition in normal state behavior accompanied by deterioration of superconductivity. On the other hand, Tl1-zPbzSr1.8Sb0.2CaCu2O7 (z = 0.1-0.6 series showed metallic normal state behaviors and enhancement in Tc zero from 26 K (z = 0.1 to a maximum of 80 K (z = 0.5. Results of structural investigation and phase formation using powder X-ray diffraction are reported and effects of Cr, Ta and Pb substitutions on superconductivity of Tl1212 are discussed in terms of ionic radius of substituting elements and the concept of average Cu valence.

  20. Manufacturing of superconductive silver/ceramic composites

    DEFF Research Database (Denmark)

    Seifi, Behrouz; Bech, Jakob Ilsted; Eriksen, Morten; Skov-Hansen, P; Wang, W.G.; Bay, Niels

    2000-01-01

    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...... current leading properties of the final superconducting fibres. The present work describes studies on alternative packing geometries and process parameters in the flat rolling operations. The aim is to obtain homogenous filaments with advantageous geometry and good texture while avoiding potential defects...... such as cracks, shear band formation and sausaging....

  1. Oxygen mobility in Bi:Sr:Ca:Cu:O ceramic measured using anelastic relaxation methods

    International Nuclear Information System (INIS)

    Since the discovery of YBaCuO, experiments have shown that its superconducting properties are strongly affected by the oxygen content. More recently, anelastic relaxation measurements in La2CuO4+δ, showed that the decrease in the oxygen content can be related to two events. One is the decrease in mobility between two adjacent CuO planes, and the other is the increase in the number of tilting patterns of the CuO6 octahedra. In the case of the bismuth-based ceramic, it is known that the oxygen content, within some limits, does not affect its superconducting properties. In order to evaluate the mobility and the effect of the oxygen content on this material we have prepared BSCCO ceramic and tested regarding its internal friction and electrical resistivity as a function of the temperature while the oxygen content was being reduced by a sequence of vacuum annealing at 620 K. The samples were prepared in the Bi:Sr:Ca:Cu=2212 and 2223 proportion, using powder obtained by the sol-gel route and conventional solid state reaction. The anelastic relaxation measurements were performed using a torsion pendulum operating with frequency about 15-35 Hz between 77 to 700 K. The diffraction pattern of the as sintered and the vacuum annealed material were also presented. The results have shown complex anelastic relaxation structures that were associated to the jump of interstitial oxygen atoms between two adjacent CuO planes. The vacuum annealing showed to be deleterious to the critical temperature of the superconducting ceramic. (orig.)

  2. Superconductivity in copper intercalated topological compound CuxBi2Te3 induced via high pressure

    International Nuclear Information System (INIS)

    Highlights: • Superconductivity was found in Cu intercalated Bi2Te3 topological insulators induced via pressures. • The copper atoms are intercalated between Te(2) and Te(2) layers confirmed by X-ray diffraction experiment. • The superconductivity of Cu0.14Bi2Te3 occurs before the pressure point of the structural transition. -- Abstract: Copper intercalated Bi2Te3 topological single crystal Cu0.14Bi2Te3 was grown using Bridgman method. The transport properties were studied by temperature dependent resistance measurements at various pressures. Pressure induced superconductivity was found with Tc for ambient phase ∼6 K. The evolutions of crystal structure with pressure were investigated by high pressure synchrotron radiation experiments that reveal structural transitions occurring above 9.8 GPa. The superconducting properties of Cu0.14Bi2Te3 are compared with that of undoped topological compound Bi2Te3

  3. 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.

  4. 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

  5. Glass-derived superconducting ceramics with zero resistance at 107 K in the Bi(1.5)Pb(0.5)Sr2Ca2Cu3O(x) system

    Science.gov (United States)

    Bansal, Narottam P.; Farrell, D. E.

    1989-01-01

    A melt of composition Bi(1.5)Pb(0.5)Sr2Ca2Cu3O(x) was fast quenched to form a glass. This was subsequently air annealed and the influence of annealing time and temperature on the formation of various crystalline phases was investigated. X-ray powder diffraction indicate that none of the resulting samples were single phase. However, for an annealing temperature of 840 C, the volume fraction of the high Tc phase (isostructural with Bi2Sr2Ca2Cu3O10) increased with annealing time. A specimen annealed at this temperature for 243 h followed by slow cooling showed a sharp transition and Tc (R = 0) = 107.2 K.

  6. 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.)

  7. Effect of pelletization pressure on structural properties and critical current hysteresis of ceramic superconducting Bi1.7Pb0.3Sr2Ca2Cu3Oy

    International Nuclear Information System (INIS)

    The effect of pelletization pressures on structural properties and critical current hysteresis of Bi1.7Pb0.3Sr2Ca2Cu3Oy 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, (Jc-H), material density vs. pressure, (ρ-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.)

  8. Superconductivity induced by current injection into non-superconducting Bi2Sr2CaCu2O8

    International Nuclear Information System (INIS)

    Unlike doping by oxygen excess, we are able to change the carrier concentration of Bi2Sr2CaCu2O8+δ (Bi2212) single crystals by carrier injection. The electrons injected along c-axis of Bi2212 are trapped in BiO and SrO layers which increases the hole concentration in CuO layers. This method gives an opportunity to observe the evolution of c-axis transport properties of Bi2212 from the antiferromagnetic state to the superconducting overdoped phase on the same sample. In order to eliminate the contact resistance, we have fabricated double cross-bar crystal stacks on fully oxygen depleted Bi2212 single crystal which was not superconducting above 4.2 K. We have observed that by carrier injection the conductivity can be increased until superconductivity above 4.2 K is reached. Continuing the doping by carrier injection, optimum-doped and even overdoped states were obtained. In the superconducting phase, the critical current density exponentially increases by doping level. At the same time, the variation of the critical temperature with doping shows a well known parabolic behavior. Doping by carrier injection offers an unique opportunity of tuning the properties of high-Tc electronic devices in situ.

  9. 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)

  10. Position dependence of the deformation state of the ceramic core in Ag/Bi-2223 tapes

    International Nuclear Information System (INIS)

    The deformation behaviour of the Bi-2223 ceramic core in an Ag/Bi-2223 composite, which is crucial for obtaining a high critical current density, has been investigated for the Ag/Bi-2223 composites where the Bi-2223 filament was located at different positions in the silver matrix. For the cores located at the mid-plane of the tape, the thickness strain and the lateral strain were large. For the cores located near the tape surface, the thickness strain and lateral strain were minimized. In a 19-filament Ag/Bi-2223 tape, the deformation state of the Bi-2223 core was less dependent on core position. It has been observed that the deformation behaviour of ceramic cores was very dependent on the core position in the silver matrix as well as the existence of the neighbouring ceramic cores. (author)

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

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

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

  12. A combined method for synthesis of superconducting Cu doped Bi2Se3.

    Science.gov (United States)

    Wang, Meng; Song, Yanru; You, Lixing; Li, Zhuojun; Gao, Bo; Xie, Xiaoming; Jiang, Mianheng

    2016-01-01

    We present a two-step technique for the synthesis of superconducting CuxBi2Se3. Cu0.15Bi2Se3 single crystals were synthesized using the melt-growth method. Although these samples are non-superconducting, they can be employed to generate high quality superconducting samples if used as precursors in the following electrochemical synthesis step. Samples made from Cu0.15Bi2Se3 reliably exhibit zero-resistance even under the non-optimal quenching condition, while samples made from pristine Bi2Se3 require fine tuning of the quenching conditions to achieve similar performance. Moreover, under the optimal quenching condition, the average superconducting shielding fraction was still lower in the samples made from pristine Bi2Se3 than in the samples made from Cu0.15Bi2Se3. These results suggest that the pre-doped Cu atoms facilitate the formation of a superconducting percolation network. We also discuss the useful clues that we gathered about the locations of Cu dopants that are responsible for superconductivity. PMID:26936470

  13. A combined method for synthesis of superconducting Cu doped Bi2Se3

    Science.gov (United States)

    Wang, Meng; Song, Yanru; You, Lixing; Li, Zhuojun; Gao, Bo; Xie, Xiaoming; Jiang, Mianheng

    2016-03-01

    We present a two-step technique for the synthesis of superconducting CuxBi2Se3. Cu0.15Bi2Se3 single crystals were synthesized using the melt-growth method. Although these samples are non-superconducting, they can be employed to generate high quality superconducting samples if used as precursors in the following electrochemical synthesis step. Samples made from Cu0.15Bi2Se3 reliably exhibit zero-resistance even under the non-optimal quenching condition, while samples made from pristine Bi2Se3 require fine tuning of the quenching conditions to achieve similar performance. Moreover, under the optimal quenching condition, the average superconducting shielding fraction was still lower in the samples made from pristine Bi2Se3 than in the samples made from Cu0.15Bi2Se3. These results suggest that the pre-doped Cu atoms facilitate the formation of a superconducting percolation network. We also discuss the useful clues that we gathered about the locations of Cu dopants that are responsible for superconductivity.

  14. 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

  15. Superconducting thin films of Bi-Sr-Ca-Cu-O obtained by laser ablation processing

    Energy Technology Data Exchange (ETDEWEB)

    Kim, B.F.; Bohandy, J.; Phillips, T.E.; Green, W.J.; Agostinelli, E.; Adrian, F.J.; Moorjani, K.; Swartzendruber, L.J.; Shull, R.D.; Bennett, L.H.; and others

    1988-07-25

    Thin films of Bi-Sr-Ca-Cu-O, deposited on (100) cubic zirconia by laser ablation from a bulk superconducting target of nominal composition BiSrCaCu/sub 2/ O/sub x/ , have been investigated by dc resistance and magnetically modulated microwave absorption measurements. The latter technique reveals important features regarding the phase purity of superconducting samples that are masked in the dc resistance measurements. The superconducting behavior of the films, as a function of the substrate temperature during deposition and the post-deposition annealing conditions, is discussed.

  16. 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

  17. Superconducting Bi-2223/Ag tapes for power applications

    International Nuclear Information System (INIS)

    Full text: Power applications of high-temperature superconductors (HTS) require the conductor to meet the following engineering specifications: (i) Jc ≥ 104 A cm-2 in the presence of a self-generated magnetic field ranging from 200 mT for power transmission cables and transformers to several tesla for superconducting magnets for mineral separation; (ii) low ac power losses, e.g. -1 for 2 kA power cables; and (iii) a strain tolerance or irreversible strain limit εIrr ≥ 0.2%. We report measurements of the electrical transport properties of Bi-2223/Ag composite conductors produced as part of the long-length product development by the Metal Manufactures Ltd - University of Wollongong - CSIRO consortium. The powder-in-tube (PIT) process was used to manufacture conductors 200 m to 1 km in length with various filament configurations including monofilament and multifilament tapes with untwisted and twisted filaments and round wires. The transport critical current Ic was measured as a function of temperature (T 4 - 80 K) and magnetic field (B = 0-9 T) for different field orientations. Self-field transport ac losses were determined at 77 K and 60 Hz as a function of ac current amplitude (0 - 100 A rms). The strain performance was evaluated at 77 K for applied bend strains from zero to 1.5 %. Scanning Hall probe magnetometry was used to image the flow of dc transport current and its distribution with increasing current to about 2Ic

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

    Science.gov (United States)

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

    1988-01-01

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

  19. Superconducting transition in TlBiTe2 and TlTe compounds

    International Nuclear Information System (INIS)

    On the basis of zone structure calculation for TlBiTe2 and TlTe it is found that TlBiTe2 is a narrow-gap semiconductor and TlTe is a p-metal. At Tsub(c)=0.19 K TlTe is found to experience the superconducting transition. In TlBiTe2 superconductivity is not observed to occur up to 0.05 K, since there is on possibility of occupying the high density of states zones because they are remote from actual ones. The earlier discovered superconducting transition in TlBiTe2 is inherent in the alien phase of TlTe

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

    Directory of Open Access Journals (Sweden)

    YOGESH A. CHAUDHARI

    2014-03-01

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

  1. 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.

  2. 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.

  3. Noncentrosymmetric superconductivity in a clean crystal of type II superconductor Bi-Pd

    Science.gov (United States)

    Ramakrishnan, Srinivasan; Pratap, Bhanu; Thamizhavel, A.

    2016-02-01

    In this work, we present the bulk superconductivity of a high-quality single crystal of monoclinic BiPd (α-BiPd, space group P21) below 3.8 K by studying its electrical resistivity, magnetic susceptibility, and heat capacity. This is the cleanest noncentrosymmetric superconductor (NCS) that display anisotropy due to spin-orbit scattering and also exhibits unusual superconducting properties due to s and p wave mixing as evidenced by the observation of Andreev bound state and multiple energy gaps via point contact measurements. In addition, Fermi surface studies suggest multiband superconductivity in this compound. Penetration depth studies and NQR investigations support mixing of s and p wave Copper paring in this crystal. Moroever, Muon spin rotation measurements indicate strong field dependence of the Ginzburg- Landau coefficient of this superconductor. Unusual pairing and multiband superconductivity are extremely sensitive to disorder and they can be observed only in cleanest (RRR > 170) single crystals.

  4. 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.

  5. 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

  6. 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...

  7. PIXE and RBS analysis of high temperature superconductivity ceramics

    International Nuclear Information System (INIS)

    Full text: Development of high temperature superconductor production technology needs measuring a set of superconductor parameters at its different stages. And noninvasive analysis and high accuracy of PIXE and RBS methods give them considerable advantages over other methods of in-process measurements. Potentialities of the methods for a study of high temperature superconductivity (HTSC) are presented in this work. Y-Ba-Cu-O ceramic plate of 1 mm thickness was used as a subject of a study. Proton beam of the EG-2 Van-de-Graaff generator built at the IAP NUU provided the measurements. The target fixed at 16-position sample holder was exposed at the proton beam formed by a collimator with beam-exit hole of 2 mm in diameter. A special monitor placed before the beam-exit hole monitored number of particles incident upon the target. Operating vacuum in the experimental chamber kept at a pressure of 8·10-6 mm Hg. 27Al(p,γ) resonance was used for energy calibration. X-ray emission was measured with a help of SL30165 type Si(Li) detector produced by Canberra Industries, Inc. that provided energy resolution of 165 eV at MnKα line. Protons backscattered at angle of 135o relatively to the beam axis were detected by a surface-barrier Si(Li) detector of PD50-12-100 type providing energy resolution of 12 KeV at energy of 5.5 MeV. Spectrometric data acquisition and processing by a Multi port 2 analyzer were controlled by Genie-2000 program

  8. 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.

  9. 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

  10. Pressure Effects on Superconducting Properties of the BiS2-Based Superconductor Bi2(O,F)S2

    Science.gov (United States)

    Okada, Tomoyuki; Ogino, Hiraku; Shimoyama, Jun-ichi; Kishio, Kohji; Takeshita, Nao; Shirakawa, Naoki; Iyo, Akira; Eisaki, Hiroshi

    2015-08-01

    Pressure effects on the recently discovered BiS2-based superconductor Bi2(O,F)S2 (Tc = 5.1 K) were examined by two different methods: high-pressure resistivity measurement and high-pressure annealing. The effects of these two methods on the superconducting properties of Bi2(O,F)S2 were significantly different, although in both methods, hydrostatic pressure is applied to the sample using a cubic-anvil-type apparatus. In high-pressure resistivity measurement, Tc linearly decreased at a rate of -1.2 K GPa-1. In contrast, the Tc of 5.1 K is maintained after high-pressure annealing under 2 GPa and 470 °C of an optimally doped sample despite a significant change in lattice parameters. In addition, superconductivity was observed in fluorine-free Bi2OS2 after high-pressure annealing. These results suggest that high-pressure annealing has a unique effect on the physical properties of layered compounds.

  11. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-03-16

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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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 pr...

  18. 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. PMID:25585392

  19. 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.

  20. 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.

  1. Electrical and magnetic properties of single-phased and highly resistive ferroelectromagnet BiFeO3 ceramic

    International Nuclear Information System (INIS)

    Investigation of BiFeO3 is being conducted intensively. However, preparing perfect samples with high resistance is still a prerequisite for the clarification of the properties of BiFeO3. Here we report electrical and magnetic properties and phase transitions of BiFeO3 ceramic synthesized by a rapid sintering processing. The dependence of the sintering products on the sintering temperatures revealed that single-phased BiFeO3 ceramic was synthesized at 880 deg, C using this rapid sintering technique. The as-prepared BiFeO3 sample shows a high resistivity of 6.7 x 1010Ω cm at an external electric field of 100 kVcm-1. Vibrating sample magnetometer (VSM) measurement verified that the high resistance BiFeO3 ceramic presented an antiferromagnetic characterization

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

    International Nuclear Information System (INIS)

    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 - Ag3Sn compound layer - PbSn2 and Ag3Sn solder layer - Ag3Sn 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.

  3. 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.

  4. 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

  5. Evidence for phonon-mediated coupling in superconducting Ba1-xKxBiO3

    International Nuclear Information System (INIS)

    Superconducting Ba1-xKxBiO3, with a Tc of 30 K, shows a large 18O 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(cgd)/kTc = 3.5 ± 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 these modes is indicated in tunneling spectroscopy. Additional results are reported, including the structural phase diagram, which suggest that superconductivity is phonon mediated

  6. 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

  7. Emergence of superconductivity in a Bi-Sr-Cu-O system

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, G.; Cieplak, M.Z.; Chien, C.L.

    1988-12-01

    Solid solutions of (Bi/sub 2-//sub x/Sr/sub x/)/sub 2/CuO/sub 6/ (0.85less than or equal toxless than or equal to1.5) have been synthesized. A metal-insulator transition is observed as the Sr composition is reduced to 0.9. The emergence of superconductivity depends critically on the minimum Sr content. Only when xgreater than or equal to0.95, does the superconductivity occur. The behavior is different from that observed in the La/sub 2-//sub x/Sr/sub x/CuO/sub 4/ system where doping La/sub 2/CuO/sub 4/ by Sr brings the system into a metallic and superconducting phase, with gradually increasing T/sub c/. .AE

  8. Emergence of superconductivity in a Bi-Sr-Cu-O system

    International Nuclear Information System (INIS)

    Solid solutions of (Bi/sub 2-//sub x/Sr/sub x/)2CuO6 (0.85≤x≤1.5) have been synthesized. A metal-insulator transition is observed as the Sr composition is reduced to 0.9. The emergence of superconductivity depends critically on the minimum Sr content. Only when x≥0.95, does the superconductivity occur. The behavior is different from that observed in the La/sub 2-//sub x/Sr/sub x/CuO4 system where doping La2CuO4 by Sr brings the system into a metallic and superconducting phase, with gradually increasing T/sub c/. .AE

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

    DEFF Research Database (Denmark)

    Bech, Jakob Ilsted; Nielsen, Morten Storgård; Eriksen, Morten; Toussaint, F.; Doremus, P.; Bay, Niels

    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...

  10. Effects of stoichiometric doping in superconducting Bi-O-S compounds

    International Nuclear Information System (INIS)

    Newly discovered Bi-O-S compounds remain an enigma in attempts to understand their electronic properties. A recent study of Bi4O4S3 has shown it to be a mixture of two phases, Bi2OS2 and Bi3O2S3, the latter being superconducting (Phelan et al 2013 J. Am. Chem. Soc. 135 5372–4). Using density functional theory, we explore the electronic structure of both the phases and the effect of the introduction of extra BiS2 bilayers. Our results demonstrate that the S2 layers dope the bismuth-sulphur bands and this causes metallisation. The bands at the Fermi level are of clear two-dimensional character. One band manifold is confined to the two adjacent, square-lattice bismuth-sulphur planes, a second manifold is confined to the square lattice of sulphur dimers. We show that the introduction of extra BiS2 bilayers does not influence the electronic structure. Finally, we also show that spin–orbit coupling does not have any significant effect on the states close to the Fermi level at the energy scale considered. (paper)

  11. Sintering of superconducting ceramics of YBa2Cu3Ox prepared by pyrolysis of carboxylates

    International Nuclear Information System (INIS)

    A systematic study is performed of the sintering process of high-tc ceramic prepared by pyrolysis of liquid metal carboxylates. Optimum conditions of sintering are: temperature 925 deg C; duration 4 hrs; air; slow cooling in the furnace. The method allows high values of superconducting transition temperature be achieved and provides a drastic transition to superconducting state due to better homogeneity and improved stoichiometry of the specimens; It is ascertained that the surface texture of the specimen and morphology of its granules affect mostly the magnitude of critical current density

  12. 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.

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

    Science.gov (United States)

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

    2016-01-01

    The discovery of two-dimensional superconductivity in Bi2Te3/FeTe heterostructures provides a new platform for the search of Majorana fermions in condensed matter systems. Since Majorana fermions are expected to reside at the core of the vortices, a close examination of the vortex dynamics in superconducting interface is of paramount importance. Here, we report the robustness of the interfacial superconductivity and 2D vortex dynamics in four as-grown and aged Bi2Te3/FeTe heterostructure with different Bi2Te3 epilayer thickness (3, 5, 7, 14 nm). After two years' air exposure, superconductivity remains robust even when the thickness of Bi2Te3 epilayer is down to 3 nm. Meanwhile, a new feature at ~13 K is induced in the aged samples, and the high field studies reveal its relevance to superconductivity. The resistance of all as-grown and aged heterostructures, just below the superconducting transition temperature follows the Arrhenius relation, indicating the thermally activated flux flow behavior at the interface of Bi2Te3 and FeTe. Moreover, the activation energy exhibits a logarithmic dependence on the magnetic field, providing a compelling evidence for the 2D vortex dynamics in this novel system. The weak disorder associated with aging-induced Te vacancies is possibly responsible for these observed phenomena. PMID:27185305

  14. 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.

  15. 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.

  16. Compressive anneal processing (CAP) of Bi2223 superconducting tapes

    International Nuclear Information System (INIS)

    The conventional processing of oxide powder-in-tube Bi2223 superconductor tapes involves iterative cycles of mechanical deformation to develop texture and reduce porosity, followed by thermal annealing to react components, relieve stress and heal cracks. However, texture and deformation hardening and cracking may limit the ability to obtain the desired grain texture through deformation alone. In addition, desintering of the oxide core occurs during annealing. We have developed a compressive anneal processing (CAP) technique in which a continuous uniaxial pressure is applied during the annealing. The new process is found to promote texture formation, enhance reaction kinetics and prevent desintering and bloating. Our initial results show that the CAP technique significantly improves the critical current density. (author)

  17. Effect of electron irradiation on magnetic properties of GdBaCuO superconducting ceramics

    International Nuclear Information System (INIS)

    Effect of irradiation with 2.2 MeV electrons on GdBaCuO high-temperature superconducting ceramics was studied. Magnetic hysteresis of samples was measured by means of vibrational magnetometer at 77 K. Visible increase of magnetic hysteresis loop is observed following irradiation. It is shown that after electron fluence up to 5x1018 cm-2, magnetic hysteresis is increased significantly (more than 50%)

  18. Preparation of various shape superconducting ceramics with various substrates by electrophoretic deposition method

    International Nuclear Information System (INIS)

    According to the electrophoretic deposition method, oxide particles can be strongly coated on various shape and size substrates which have a conductive surface. The YBCO superconducting ceramics wires and plates were prepared by using this method. After the fine powder of superconductive oxides was deposited on a Ag wire substrate, the wire was heat-treated at 940 C for 1h. Then the coated material was removed and pulverized, and analyzed by the X-ray diffraction method. The spectra coincided completely with that of YBa2Cu3O7-δ. The diamagnetic shift started at 93K. Moreover, the resistivity of the superconducting oxides coated Ag wire changed from 0.8X10-6 to 10-8 ω·cm (Current:10mA) at about 90K. In the case of nonconductive substrate, e.g., an Al2O3 ceramics plate, it was coated with metal, e.g., silver, by the electroless plating method. Then it was treated as stated above. This also showed completely the YBCO superconductive characteristics

  19. 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.

  20. ANTIFERROMAGNETIC TO PARAMAGNETIC PHASE TRANSITIONS IN BISMUTH FERRITE (BiFeO3 CERAMICS BY SOLID STATE REACTION

    Directory of Open Access Journals (Sweden)

    Chandrashekhar P. Bhole

    2012-07-01

    Full Text Available This paper describes the synthesis of multiferroic BiFeO3 ceramics was prepared by solid state reaction and high energy ball milling method. The structural studies was carried out by using an X-ray diffraction pattern and demonstrated that the BiFeO3 ceramic crystallizes in a rhombhohedral perovskite phase. The ferroelectric hystersis loop measured at room temperature demonstrates a lossy loop with unsaturated behavior and symbolize a partial reversal of polarization. A dielectric constant with temperature measurement for BiFeO3 ceramic represents an anomaly around 350°C for all frequencies and intimately associated with antiferromagnetic to paramagnetic phase transition (TN of BiFeO3.

  1. 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.)

  2. Preparation and characterization of glossy and superconducting (Bi, Pb, Sb)-Sr-Ca-Cu-O systems

    International Nuclear Information System (INIS)

    Superconducting compounds with nominal compositions Bisub(1.7)Pbsub(0.3) Srsub(1.6)Ca2Cusub(3.4)Ox and Bisub(1.9)Sbsub(0.1)Sr2Ca2Cu3Oy have been synthesized by ceramic and glass routes and characterized by X-ray diffraction, electrical resistivity and dielectric constant measurements. The zero-electrical resistance temperatures are about 70 K. The dielectric constant of the glasses at room temperature is around 30. (author). 5 refs., 8 figs

  3. 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

  4. 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.

  5. 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.

  6. Current leads based on the Bi-223 HTSC for superconducting magnets

    International Nuclear Information System (INIS)

    The IHEP experience in the area of developing and manufacturing the current leads, intended for the particles accelerator superconducting magnets is summarized. The brief review of the 600 A current leads produced on the basis of the belt composite conductor with the Bi-2223 threads in the matrix from the Ag+1 at. % Au and Ag+10 at. % Au alloys is given. The results of studies on the current leads electrical and thermal properties are presented. The current leads showed their high stability in operation and reliability by the short-time overloading by the current

  7. 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.

  8. Effect of Structural Transition on Magnetic Properties of Ca and Mn co-substituted BiFeO3 Ceramics

    OpenAIRE

    Kumar, Pawan; Kar, Manoranjan

    2014-01-01

    Composition-driven structural transitions in Bi1-xCaxFe1-xMnxO3 ceramics prepared by the tartaric acid modified sol-gel technique have been studied to analyze its effect on the magnetic properties of bismuth ferrite (BiFeO3). It was observed that the co-substitution of Ca & Mn at Bi & Fe sites in BiFeO3 (BFO) significantly suppress the impurity phases. The quantitative crystallographic phase analysis has been carried out by double phase Rietveld analysis of all the XRD patterns which indicate...

  9. 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.

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

    International Nuclear Information System (INIS)

    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

  11. 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. PMID:21694057

  12. Ceramic insulation for superconducting Nb3Sn cables

    International Nuclear Information System (INIS)

    Nb3Sn 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 Nb3Sn compounds. The conventional insulation for Nb3Sn 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 Nb3Sn 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)

  13. Magnetoresistance oscillations in Bi2Te3 microwires contacting with superconducting InGa

    International Nuclear Information System (INIS)

    Full text: Recent efforts to detect and manipulate Majorana fermions in solid state devices have employed topological insulator nanowires proximity coupled to superconducting leads. We studied the transverse magnetoresistance (TMR) of the contact between in polycrystal Bi2Te3 nanowires with a diameter d=16 microns in contact with superconducting InGa and we report observing a very unusual phenomenon. The microwire samples of n-type Bi2Te3 with a glass coating were manufactured by liquid phase casting in a glass capillary using an improved Taylor technique. The samples with a length of L ∼ 2 mm were prepared by cutting them from a long microwire. Contacts to the copper current leads were made using eutectic InGa, a technique that yields very low contact resistance. InGa becomes superconducting at about 4 K, depending on the ratio of the components. It is possible that, because of the diffusion of InGa from the contact area to the gap between the core and the glass insulation on the surface of the Bi2Te3 core, a thin cylindrical superconducting film with a width of about 50 microns was formed. At low temperatures (1.5 K-4.2 K) in a wide range of magnetic fields up to 2 T nonmonotonic changes of TMR that are equidistant in the direct magnetic field were observed. The period of oscillations ΔB ∼ 0.12 T. Than the magnetic field is increased, the oscillation amplitude decreases and the oscillation period decreases gradually with each extremum of about 7-8%. The observed oscillations cannot be referred to the Shubnikov de Haas oscillations because of they are not periodic in the inverse magnetic field and their amplitude with increasing magnetic field decreases. We also discuss the conditions under which the unusual behavior that is observed can be considered an Aharonov-Bohm effect associated with a unintended small diameter constriction or a vortex within the contact.

  14. 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.

  15. Rietveld analysys and electrical properties of lanthanum doped BiFeO3 ceramics

    International Nuclear Information System (INIS)

    Lanthanum-modified bismuth ferrite ceramics, Bi1-xLaxFeO3 (BLFO), with x ranging from 0 to 0.30 were obtained using a polymeric precursor solution. Orthorhombicity of the system raised with the increase of lanthanum content in the BFO crystal lattice. No secondary phases were evident after lanthanum addition. This study underlines the role of the preparation route on the structural and morphological characteristic of the obtained materials and their influence on the electrical behavior. A homogeneous size distribution of BFO powders was evidenced by scanning electron microscopy. Increasing lanthanum content leads to lower leakage current density and superior ferroelectric hysteresis loops at room temperature.

  16. 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...

  17. 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.

  18. 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...

  19. Advances in development of Ag-clad Bi-based superconducting tapes

    International Nuclear Information System (INIS)

    Full text: Significant advances in development of the Ag-clad Bi-based superconducting tapes have been recently achieved by the Wollongong group. These include understanding of the effect of initial phase composition on sintering temperature, formation mechanism of high Tc phase, control of sausaging formation during rolling and effect of atmosphere on microstructure of the tapes. Techniques such as 'sandwich rolling' process have been developed to prevent the formation of sausaging and cracks in longitudinal direction of the Ag-clad Bi-based superconducting tapes. High Jc for Ag/Bi-2212 tapes achieved through MTG in the alternating oxygen and nitrogen atmosphere. While N2 annealing on cooling ensures high Tc, O2 treatment during melting period enhances the stability of 2212, allowing for grain growth with ample liquid formation. Direct observation of the interface achieved by removing Ag sheath with Hg alloy shows highly dense, textured and thin-film like structure. Ca2PbO4 was found to have significant effect of sintering temperature. Incorporation of Ca2PbO4 into 2212 phase can reduce the duration of 2223 tape process to below 100 h, resulting high Jc with a record performance in magnetic field. 23.4% of zero field Jc value was retained in 1T. Grain growth in 2223 tape must be well controlled in order to optimise Jc. Features of 2212 tape and 2223 tape are compared in terms of their processing, microstructure and electromagnetic properties. Potential strong links in the tape are proposed to be the low angle tilt boundaries where the Cu-O planes are well connected. The pinning potential, Uo, for 2223 tape, determined by using magnetoresistance measurements, is larger than that for the best 2212 tape and epitaxial thin films while Uo for the latter is, in turn, higher than 2212 single crystal. This may be attributed to the difference in dislocation density in these materials

  20. First single crystal growth and structural analysis of superconducting layered bismuth oxyselenide; La(O,F)BiSe2

    International Nuclear Information System (INIS)

    Single crystals of La(O,F)BiSe2 were successfully grown for the first time by a CsCl flux method. Single crystal X-ray structural analysis clearly showed that La(O,F)BiSe2 crystallizes with space group P4/nmm (lattice parameters a=4.1408(2) Å, c=14.1096(6) Å). The structure is composed of alternating BiSe2 and La(O,F) layers. The bond distances and angles are similar to those of La(O,F)BiS2. The bond valence sum calculation indicates the refined structure is slightly cation rich, suggesting the charge neutrality should be kept by modification of valence state of the cations. Magnetic susceptibility and resistivity measurements showed the compound is a superconductor with a transition temperature of 3.6 K, which is higher than that of as-grown La(O,F)BiS2. - Graphical abstract: Single crystal La(O,F)BiSe2 has been prepared by a CsCl flux method. The structural analysis implies that La(O,F)BiSe2 is a potential superconductor having a higher Tc under high pressure. - Highlights: • Single crystals of La(O,F)BiSe2 were grown by a CsCl flux method. • Crystal structure of La(O,F)BiSe2 was determined by single crystal X-ray analysis. • La(O,F)BiSe2 shows superconductivity with a transition temperature of 3.6 K. • Bonding nature and superconductivity of La(O,F)BiSe2 are discussed

  1. 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.

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

    International Nuclear Information System (INIS)

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

  3. 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

  4. 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.

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

    International Nuclear Information System (INIS)

    Highlights: • Effect of YBCO addition on the superconductivity in Bi1.6Pb0.4Sr2Ca2Cu3Oδ. • 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 Bi1.6Pb0.4Sr2Ca2Cu3Oδ (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 TC 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 (TP) gradually decreased to lower temperature from 107.0 K to 108.5 K

  6. 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.

  7. Crystal Structure, Lattice Vibrations,and Superconductivity of LaO1-xFxBiS2

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jooseop [ORNL; Stone, Matthew B [ORNL; Huq, Ashfia [ORNL; Yildrim, Tanner [NIST Center for Neutron Research (NCRN), Gaithersburg, MD; Ehlers, Georg [ORNL; Mizuguchi, Y [National Institute for Materials Science, Tsukuba, Japan; Miura, O [Tokyo Metropolican University; Takano, Y [National Institute for Materials Science, Tsukuba, Japan; Demura, S [National Institute for Materials Science, Tsukuba, Japan; Lee, Seung Hyun [ORNL

    2013-01-01

    Neutron scattering measurements have been performed on polycrystalline samples of the newly discovered layered superconductor LaO0:5F0:5BiS2, and its nonsuperconducting parent compound LaOBiS2. The crystal structures and vibrational modes have been examined. Upon F-doping, while the lattice contracts signicantly along c and expands slightly along a, the buckling of the BiS2 plane remains almost the same. In the inelastic measurements, a large dierence in the high energy phonon modes was observed upon F substitution. Alternatively, the low energy modes remain almost unchanged between non-superconducting and superconducting states either by F- doping or by cooling through the transition temperature. Using density functional perturbation theory we identify the phonon modes, and estimate the phonon density of states. We compare these calculations to the current measurements and other theoretical studies of this new superconducting material.

  8. 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. PMID:27010099

  9. 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.

  10. 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

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

    Science.gov (United States)

    Hooker, Matthew W.; Taylor, Theodore D.

    1994-01-01

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

  12. 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.

  13. The structure and piezoelectric properties of (Ca1-xSrx)Bi4Ti4O15 ceramics

    International Nuclear Information System (INIS)

    In this paper, the structure and piezoelectric properties of (Ca1-xSrx)Bi4Ti4O15 ceramics (x=0-1.0) are investigated. The formation of single orthorhombic phase is verified by XRD. The dependence of dielectric and piezoelectric properties on x is also determined. The results show that the excellent properties could be found in the composition of x=0.4. In that composition, d33=14.9, TC=677 deg. C and the DC resistivity is decuplely higher than that of BST (SrBi4Ti4O15) and CBT (CaBi4Ti4O15)

  14. Influence of Zr4+ doping on structural and electrical properties of SrBi4Ti4O15 ceramic

    Science.gov (United States)

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

    2015-06-01

    This article reports a systematic study of doping effects on the structural and electrical properties of layer structured strontium bismuth titanate ceramic. In this study monophasic SrBi4Ti4-xZrxO15 with x=0.00, 0.05, 0.10, 0.15, 0.20, 0.25 ceramics were synthesized from the solid-state reaction route. X-ray diffraction analysis shows that the Zr-modified SBT ceramics have a pure four-layer Aurivillius phase structure. Dielectric properties revealed that the diffuseness of phase transition increases where as corresponding permittivity value decrease with increasing Zr content. Piezoelectric properties of SBTZ ceramics were improved by the modification of Zirconium ion. Moreover, the reason behind for improvement of piezoelectric properties of modified SBTZ ceramics was also discussed.

  15. Influence of Zr4+ doping on structural and electrical properties of SrBi4Ti4O15 ceramic

    International Nuclear Information System (INIS)

    This article reports a systematic study of doping effects on the structural and electrical properties of layer structured strontium bismuth titanate ceramic. In this study monophasic SrBi4Ti4-xZrxO15 with x=0.00, 0.05, 0.10, 0.15, 0.20, 0.25 ceramics were synthesized from the solid-state reaction route. X-ray diffraction analysis shows that the Zr-modified SBT ceramics have a pure four-layer Aurivillius phase structure. Dielectric properties revealed that the diffuseness of phase transition increases where as corresponding permittivity value decrease with increasing Zr content. Piezoelectric properties of SBTZ ceramics were improved by the modification of Zirconium ion. Moreover, the reason behind for improvement of piezoelectric properties of modified SBTZ ceramics was also discussed

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

    International Nuclear Information System (INIS)

    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

  17. 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

  18. 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.

  19. Optimization of the Processing Parameters of High Temperature Superconducting Glass-Ceramics: Center Director's Discretionary Fund Final Report

    Science.gov (United States)

    Ethridge, E. C.; Kaukler, W. F.

    1993-01-01

    A number of promising glass forming compositions of high Tc superconducting Ba-Sr-Ca-Cu-O (BSCCO) materials were evaluated for their glass-ceramic crystallization ability. The BSCCO ceramics belonging to the class of superconductors in the Ba-Sr-Ca-Cu-O system were the focus of this study. By first forming the superconducting material as a glass, subsequent devitrification into the crystalline (glass-ceramic) superconductor can be performed by thermal processing of the glass preform body. Glass formability and phase formation were determined by a variety of methods in another related study. This study focused on the nucleation and crystallization of the materials. Thermal analysis during rapid cooling aids in the evaluation of nucleation and crystallization behavior. Melt viscosity is used to predict glass formation ability.

  20. Stability of proton-irradiated superconducting yttrium ceramics to atmospheric degradation

    International Nuclear Information System (INIS)

    Full text: Yttrium cuprate tetra-phase is known to be much more stable than the ortho-one under the ambient conditions. Here we present the results of studying the time stability of the structure and superconducting properties of isotropic yttrium cuprate ceramics YBa2Cu3O7-δ (δ ≅ 0.05) irradiated with high energy protons. The structure characteristics of samples were determined at the diffractometer DRON-UM1 (λCuKα = 1.54178 A). Electrophysical parameters were measured with the four-probe technique at the direct current of 10 mA. The ceramic pellets of 12 mm in diameter and 0.6 mm of thickness, with the average grain size of 14 μm, the lattice parameters ar ≅ 3.822, br≅ 3.883 and cr ≅ 11.673 A, the density ∼ 5.1 g.cm-3, the specific resistance ∼3 mΩ· cm in the normal state, had the superconducting Tc ≅ 91 K. The samples were irradiated at the cyclotron U-150 of the INP AS RUz with 18 MeV-protons within the range of fluences 1014 - 1015 cm-2 at the beam current of 20 nA and 300 K. During a 6-months-ageing at 300 K the structure and electric measurements were carried out every two weeks. Comparative analysis of the results showed the correlation between the changes of the I012 / I102 intensity ratio for reflections (012) and (102) and the specific resistivity. For 6 months the maximal growth of the values of ρ by 97 % and I012 / I102 by 3.1 % occurred for the non-irradiated ceramics. The growth of these values for the samples irradiated to doses within (2 4) 1014 cm-2 came to 7.9 and 1.9 %, respectively. The critical temperature Tc for the non-irradiated samples decreased by 2.2 K, and for the irradiated ones only by 0.8 K. The observed difference in the stability of non-irradiated and irradiated samples can be explained in the frame of the granular structure model. Moderate proton fluences cause the radiation-induced phase transition ortho-tetra in the contact layer between grains that provides the increase of the irradiated ceramics stability

  1. Crystallographic and magnetic identification of secondary phase in orientated Bi5Fe0.5Co0.5Ti3O15 ceramics

    International Nuclear Information System (INIS)

    The fabrication of highly-oriented polycrystalline ceramics of Bi5Fe0.5Co0.5Ti3O15, prepared via molten salt synthesis and uniaxial pressing of high aspect ratio platelets is reported. Electron backscatter images show a secondary phase within the ceramic which is rich in cobalt and iron. The concentration of the secondary phase obtained from scanning electron microscopy is estimated at less than 2% by volume, below the detection limit of x-ray diffraction (XRD). The samples were characterized by x-ray diffraction, polarization-electric field measurements, superconducting quantum interference device as a function of sample orientation and vibrating sample magnetometry as a function of temperature. It is inferred from the data that the observed ferromagnetic response is dominated by the secondary phase. This work highlights the importance of rigorous materials characterisation in the study of multiferroics as small amounts of secondary phase, below the limit of XRD, can lead to false conclusions.

  2. 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

  3. 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.

  4. Performance of Titanium-Oxide/Polymer Insulation in Bi-2212/Ag-alloy Round Wire Wound Superconducting Coils

    OpenAIRE

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

    2013-01-01

    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 analy...

  5. Effect of Structural Transition on Magnetic and Dielectric Properties of La and Mn co-substituted BiFeO3 Ceramics

    OpenAIRE

    Kumar, Pawan; Kar, Manoranjan

    2014-01-01

    Bi1-xLaxFe1-xMnxO3 (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 (BiFeO3). It was found that the co-substitution of La & Mn at Bi & Fe sites leads to suppression of impurity phases (Bi2Fe4O9 and Bi25FeO40) which generally appear in BiFeO3. The quantitative crystallographic phase analysis has been carried out by double phase R...

  6. Dissipation in current-carrying high-Tc superconducting ceramics in applied magnetic field

    International Nuclear Information System (INIS)

    The dissipation mechanism in high-Tc superconducting ceramics was studied by analyzing the magnetic field dependence of the transport critical current and the form of the current-voltage characteristics. It was found that the actual magnetic field dependence of the transport critical current is significantly slower than that predicted by the weak-link-quenching model. The low-voltage-level current-voltage characteristics were described in terms of thermally activated flux creep at grain boundaries, taking into account collective pinning of intergranular Josephson vortices. For the investigated samples, a low-field, high-temperature mean pinning energy barrier of a few tens of meV was determined. 21 refs., 8 figs

  7. Interstitial oxygen mobility in superconducting samples of Bi2Sr2CaCu2O8+y

    International Nuclear Information System (INIS)

    Since high-temperature superconductors were discovered, several studies have been made on their physical properties, attempting to associate them to the origin of superconductivity. Obviously, the oxygen atoms interstitially dissolved in the matrix have an important role in superconductivity, since they move easily in the lattice. In addition, they contribute to hole creation in the CuO2 planes. Anelastic spectroscopy (internal friction) measurements are sensitive tools for the study of defects in solids, in particular for oxygen mobility. In this paper, Bi2Sr2CaCu2O8+y samples with several different amounts of interstitial oxygen were analysed by means of anelastic spectroscopy measurements. The measurements were performed by using a torsion pendulum operating at a frequency of about 40 Hz. Complex relaxation structures were observed and attributed to the shift of the oxygen interstitial atoms in BiO chains

  8. Superconductivity up to 114 K in the Bi-Al-Ca-Sr-Cu-O compound system without rare-earth elements

    Science.gov (United States)

    Chu, C. W.; Bechtold, J.; Gao, L.; Hor, P. H.; Huang, Z. J.

    1988-01-01

    Stable superconductivity up to 114 K has been reproducibly detected in Bi-Al-Ca-Sr-Cu-O multiphase systems without any rare-earth elements. Pressure has only a slight positive effect on T(c). These observations provide an extra material base for the study of the mechanism of high-temperature superconductivity and also the prospect of reduced material cost for future applications of superconductivity.

  9. Near-infrared Luminescence Properties of Bi2O3-SiO2 Glasses and Glass Ceramics

    Directory of Open Access Journals (Sweden)

    LIU Jun-Fang, SU Liang-Bi, XU Jun

    2014-08-01

    Full Text Available Bi2O3-SiO2 glasses and glass ceramics were prepared by melting method. Infrared and VIS luminescence spectra, excitation spectra and fluorescence decay curves were measured. Near infrared (NIR luminescence ofBi2O3-SiO2 glasses and glass ceramics was observed under 808 nm Laser Diode pumping. When the content of Bi2O3 is low (30mol%, 40mol%, 50mol%, NIR luminescence peak at 1336 nm (or 1300 nm with full width at half maximum (FWHM about 200 nm is observed. With the increase of Bi2O3 content, another peak at about 1070 nm with narrow FWHM appears and becomes the main peak, while the FWHM of the NIR emission centered at 1336 nm (or 1300 nm decreases to only tens of nanometer. Two emission bands have different excitation bands and lifetime. We propose NIR emissions located at 1070 nm and 1336 nm (or 1300 nm originate from different bismuth centers. The infrared emission peaked at about 1336 nm (or 1300 nm derives from low valence Bi ions.

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

    International Nuclear Information System (INIS)

    Bending behavior of Bi2223/Ag superconducting composite tapes, and the influence of the bending damages on critical superconducting current Ic 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 Ic and n-value in the corresponding local portion. The overall Ic 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.)

  11. 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.)

  12. 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.

  13. 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.)

  14. In situ preparation of superconducting Bi(Pb)SrCaCuO thin films by magnetron sputtering in pure oxygen

    International Nuclear Information System (INIS)

    As-grown superconducting thin films of Bi(Pb)SrCaCuO were prepared on MgO (100) by dc magnetron sputtering. The target used was a single sintered Bi(Pb)SrCaCu composite oxide. The deposition rate was about 1.4 A/s. The sputtering gas was pure oxygen at 0.3 Torr. The deposition process, followed by quenching in pure oxygen, yielded c-axis oriented superconducting thin films with a smooth surface. The superconducting properties of the films were improved by increasing the oxygen pressure during quenching. The superconducting properties of the films are very sensitive to the substrate temperature, which ranged from 620-740 C during film growth. The c-axis lattice constant of the films could also be controlled to values of about 24, 31 and 37 A simply by changing the substrate temperature. The lead concentration in the films apparently decreased with an increase in substrate temperature, becoming almost zero above 660 C. However, the relative cationic ratio of the other elements in the films was close to that of the target regardless of the substrate temperature. Films deposited above 700 displayed the 37 A phase. The best film deposited at 720 C showed zero resistivity at 81 K and the critical current density increased from 8x104 A/cm2 at 77 K to 3x106 A/cm2 at 4.2 K. (orig.)

  15. Broadband photoluminescence of Bi2O3–GeO2 binary systems: glass, glass-ceramics and crystals

    International Nuclear Information System (INIS)

    Ultra-broadband emission covering 1000–1800 and 1800–3020 nm of Bi2O3–GeO2 binary system materials, from glass to glass-ceramics to crystals, is presented in this paper. This is the first time, to our best knowledge, that broadband photoluminescence of BGO crystals (including Bi4Ge3O12 and Bi12GeO20) in the range of 1800–3020 nm has been realized. HRTEM, XPS and XANES have been used to investigate the effects of the valence states and the structure environment of bismuth on the emission properties of Bi2O3–GeO2 binary system materials. Bi2+ and Bi+ are proposed as the emission centers of the photoluminescence peaks at 1060 and 1300 nm, respectively. The broadband emission from 1800 to 3020 nm originates from bismuth clusters. Bi2O3–GeO2 binary system materials could be promising laser materials in the field of full-band optical fiber communication amplifiers, ultra-fast lasers and diode pumped solid state lasers, due to their broadband emission spectra and their feasibility of synthesis and drawing into fibers. (paper)

  16. 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

  17. 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.

  18. 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)

  19. 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.

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

    Science.gov (United States)

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

    1995-01-01

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

  1. 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.

  2. Room temperature structure and multiferroic properties in Bi0.7La0.3FeO3 ceramics

    International Nuclear Information System (INIS)

    Highlights: ► We obtain reproducible results in ceramics synthesized by different methods. ► We report an incommensurate modulated structure for Bi0.7La0.3FeO3 ceramics. ► We report the piezoelectric coefficient for this composition. ► The obtain structure is related with Raman spectra and ferroelectric properties. -- Abstract: Single phase Bi0.7La0.3FeO3 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 Bi0.7La0.3FeO3 composition

  3. 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

  4. Effect of orthorhombic distortion on dielectric and piezoelectric properties of CaBi4Ti4O15 ceramics

    International Nuclear Information System (INIS)

    High temperature bismuth layered piezoelectric and ferroelectric ceramics of CaBi4Ti4O15 (CBT) have been prepared using the solid state route. The formation of single phase material with orthorhombic structure was verified from x-ray diffraction and Raman spectroscopy. The orthorhombic distortion present in the CBT ceramic sintered at 1200 deg. C was found to be maximum. A sharp phase transition from ferroelectric to paraelectric was observed in the temperature dependent dielectric studies of all CBT ceramics. The Curie's temperature (Tc=790 deg. C) was found to be independent of measured frequency. The behavior of ac conductivity as a function of frequency (100 Hz-1 MHz) at low temperatures (33). The observed results indicate the important role of orthorhombic distortion in determining the improved property of multicomponent ferroelectric material.

  5. 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.

  6. 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.

  7. 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)

  8. 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.

  9. 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.

  10. Particle flow of ceramic breeder pebble beds in bi-axial compression experiments

    International Nuclear Information System (INIS)

    Pebble beds of Tritium breeding ceramic material are investigated within the framework of developing solid breeder blankets for future nuclear fusion power plants. For the thermo-mechanical characterisation of such pebble beds, bed compression experiments are the standard tools. New bi-axial compression experiments on 20 and 30 mm high pebble beds show pebble flow effects much more pronounced than in previous 10 mm beds. Owing to the greater bed height, conditions are reached where the bed fails in cross direction and unhindered flow of the pebbles occurs. The paper presents measurements for the orthosilicate and metatitanate breeder materials that are envisaged to be used in a solid breeder blanket. The data are compared with calculations made with a Drucker-Prager soil model within the finite-element code ABAQUS, calibrated with data from other experiments. It is investigated empirically whether internal bed friction angles can be determined from pebble beds of the considered heights, which would simplify, and broaden the data base for, the calibration of the Drucker-Prager pebble bed models

  11. 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.

  12. 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

  13. Superconductivity in the orthorhombic phase of thermoelectric CsPbxBi4-xTe6 with 0.3≤x≤1.0

    Science.gov (United States)

    Zhang, R. X.; Yang, H. X.; Tian, H. F.; Chen, G. F.; Wu, S. L.; Wei, L. L.; Li, J. Q.

    2015-12-01

    Experimental measurements clearly reveal the presence of bulk superconductivity in the CsPbxBi4-xTe6 (0.3≤x≤1.0) materials, i.e. the first member of the thermoelectric series of Cs[PbmBi3Te5+m], these materials have the layered orthorhombic structure containing infinite anionic [PbBi3Te6]- slabs separated with Cs+ cations. Temperature dependences of electrical resistivity, magnetic susceptibility, and specific heat have consistently demonstrated that the superconducting transition in Cs0.96Pb0.25Bi3.75Te6.04 occurs at Tc=3.1 K, with a superconducting volume fraction close to 100% at 1.8 K. Structural study using aberration-corrected STEM/TEM reveals a rich variety of microstructural phenomena in correlation with the Pb-ordering and chemical inhomogeneity. The superconducting material Cs0.96Pb0.25Bi3.75Te6.04 with the highest Tc shows a clear ordered structure with a modulation wave vector of q≈a*/2+c*/1.35 on the a-c plane. Our study evidently demonstrates that superconductivity deriving upon doping of narrow-gap semiconductor is a viable approach for exploration of novel superconductors.

  14. 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}).

  15. Ferroelectric and dielectric properties of Sr2-x(Na, K)xBi4Ti5O18 lead-free piezoelectric ceramics

    International Nuclear Information System (INIS)

    (Na, K)-doped Sr2Bi4Ti5O18 (SBTi) bismuth layer structure ferroelectric ceramics were prepared by the solid-state reaction method. Pure bismuth-layered structural Sr2-x(Na, K)xBi4Ti5O18 (x=0.1, 0.2, 0.3, and 0.4) ceramics with uniform grain size were obtained in this work. The effects of (Na, K)-doping on the dielectric, ferroelectric and piezoelectric properties of SBTi ceramics were investigated. Results showed that (Na, K)-doping caused the Curie temperature of SBTi ceramics to shift to higher temperature and enhanced the ferroelectric and piezoelectric properties. At x=0.2, the ceramics exhibited optimum properties with d33=20 pC/N, Pr=10.3 μC/cm2, and Tc=324 oC.

  16. Superconductivity-Induced Self-Energy Evolution of the Nodal Electron in Optimally-Doped Bi2212

    Energy Technology Data Exchange (ETDEWEB)

    Lee, W.S.

    2010-05-03

    The temperature dependent evolution of the renormalization effect in optimally-doped Bi2212 along the nodal direction has been studied via angle-resolved photoemission spectroscopy. Fine structure is observed in the real part of the self-energy (Re{Sigma}), including a subkink and maximum, suggesting that electrons couple to a spectrum of bosonic modes, instead of just one mode. Upon cooling through the superconducting phase transition, the fine structures of the extracted Re{Sigma} exhibit a two-processes evolution demonstrating an interplay between kink renormalization and superconductivity. We show that this two-process evolution can be qualitatively explained by a simple Holstein model in which a spectrum of bosonic modes is considered.

  17. Phases and structural characteristics of high Tc superconducting oxide in (Bi, Pb)-Sr-Ca-Cu-O system

    International Nuclear Information System (INIS)

    The various phases, which are responsible for variant maximum d-value including 18.5 angstrom, 15.4 angstrom, 12.2 angstrom, 6.2 angstrom, 3.2 angstrom and possible 9.1 angstrom respectively, observed in high Tc superconducting complex oxide of (Bi,Pb)-Sr-Ca-Cu-O system are reported in this paper according to the result of X-ray diffraction on platelike crystals or crystallites synthesized under different preparation conditions. The phase of tetragonal system with c=3.21 angstrom, a=3.86 angstrom is possible parent structural unit and it is of great significance to the structure constitution of various phases with large lattice parameter c and structural characteristics of superconducting oxide. In view of the above a model of two-dimension stack-up which causes a stack in variant styles along c-axis and constitute various phases with different lattice parameter c is proposed and discussed

  18. Method for preparing rare earth-barium-cuprate pre-ceramic resins and superconductive materials prepared therefrom

    International Nuclear Information System (INIS)

    This patent describes a method of making a pre-ceramic material capable of being converted into an electrically superconductive ceramic material having the general formula ABa2Cu3O7-x where A is a rare earth metal and x is from 0 to 0.5. It comprises refluxing stoichiometric amounts of a first solution comprising a rare earth isopropoxide and barium isopropoxide in isopropanol under a dry, inert atmosphere; adding to the first solution a stoichiometric amount of a second solution comprising copper ethylhexanoate in isopropanol; refluxing the first and second solutions to obtain a precipitate; adding to the precipitate a quantity of a first solvent comprising water and isopropanol; concentrating the homogeneous solution by removing a sufficient amount of the first solvent to produce a viscous or dry pre-ceramic resinous material; softening or dissolving the pre-ceramic resinous material in a second solvent comprising a binary mixture of a polar solvent and a nonpolar solvent to obtain a desired viscosity; and forming the viscous pre-ceramic material into the desired product shape

  19. 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.

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

    Science.gov (United States)

    Liu, R.; Qu, T.-M.; Zhang, J.-S.; Song, X.-H.; Liang, T.; Liu, Q.; Han, Z.

    2008-09-01

    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 ( Ic) 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 Ic and engineering critical current density ( Je) values of HTS tapes.

  1. 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.

  2. 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)

  3. 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)

  4. 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

  5. Stabilization of dielectric anomaly near the magnetic phase transition in Ca2+ doped BiFeO3 multifunctional ceramics

    International Nuclear Information System (INIS)

    Highlights: ► Stabilization of hitherto unreported dielectric peak near magnetic transition in Bi1−xCaxFeO3. ► The phenomenon is predominantly due to “skin effect” confined to top few layers of the sample. ► There is enhancement in magneto-electric coupling as a function of dopant concentration. ► New and easy measurement method to show presence of magneto-electric coupling is proposed. -- Abstract: Stabilization of a prominent peak in the variation of dielectric constant in Ca2+ doped BiFeO3 ceramics near the antiferromagnetic to paramagnetic phase transition is reported. Temperature dependent dielectric data also shows perceptible frequency dispersion starting from temperatures well below the Neel temperature. This observation has been explained in terms of “skin effect”. Clear signature of magneto-electric coupling is shown using the P–E loops measurement of magnetically poled samples. The presence of magneto-electric coupling is explained in terms of the modulation of canted spin structure. Using Rietveld refinement of X-ray and neutron data, it is shown that the rhombohedral distortion decreases with increasing Ca2+ content. Analysis of SQUID–VSM magnetic hysteresis data proves the occurrence of structure induced anti-ferromagnetic to weak ferromagnetic transition. Significance of these observations for future applications of divalent doped BiFeO3 ceramics is also discussed

  6. 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).

  7. Synthesis-phase–composition relationship and high electric-field-induced electromechanical behavior of samarium-modified BiFeO3 ceramics

    International Nuclear Information System (INIS)

    Solid-state (non-activated) and mechanochemical activation (activated) synthesis methods were used to produce Sm-modified BiFeO3 ceramics of composition Bi0.88Sm0.12FeO3. The first part shows that the formation of Bi0.88Sm0.12FeO3 using the two synthesis methods followed a different reaction pathway on annealing the powders. The non-activated ceramics reacted by forming two intermediate phases, isostructural to BiFeO3 and SmFeO3, and then inter-diffusing, forming the final Bi0.88Sm0.12FeO3 solid solution. Unlike the non-activated samples, the activated ceramic powders formed Bi0.88Sm0.12FeO3 phase on annealing the powders, without apparent intermediate phases. As revealed by transmission electron microscopy, the non-activated reaction pathway caused the Pbam phase to form as chemical inhomogeneous (Sm-rich) isolated nano-sized grain inclusions in the final ceramics. Conversely, the activated reaction pathway caused the Pbam phase to form chemically homogeneous nano-regions within the R3c phase grains. The results demonstrate the important role of processing in the appearance of the frequently discussed anti-polar Pbam phase in this system. In the second part, the high electric-field-induced polarization and strain behaviors of these ceramics were studied by means of polarization–electric (P–E) and strain–electric field (S–E) hysteresis loops, and the S–E loops were compared with those of unmodified BiFeO3. Bipolar S–E loops of Bi0.88Sm0.12FeO3 had a distinctive butterfly shape with less frequency dependence relative to BiFeO3 at driving-field frequencies of 0.1–100 Hz. BiFeO3 ceramics exhibite strong driving electric-field-frequency-dependent domain switching, the origins of which were previously attributed to a domain-wall pinning mechanism and “hardening” behavior. This study shows that Sm-modification induces a “hardening–softening” transition in BiFeO3 ceramics

  8. 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.

  9. 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.

  10. Photoluminescence, enhanced ferroelectric, and dielectric properties of Pr3+-doped SrBi2Nb2O9 multifunctional ceramics

    International Nuclear Information System (INIS)

    Pr3+-doped SrBi2Nb2O9 (SBN) multifunctional ceramics were synthesized by the conventional solid state method. The photoluminescence (PL) excitation and emission spectra, enhanced ferroelectric and dielectric properties were investigated. The X-ray diffraction (XRD) and FESEM analyses indicated that the samples were simple phase and uniform flake-structure. Under the 250–350 nm ultraviolet (UV) excitations, the red emission was obtained and the optimal emission intensity was investigated when Pr doping level was 0.005 mol. With the increasing of the Pr3+ ion contents, the ferroelectric properties were enhanced obviously. As a new multifunctional material, the Pr3+-doped SBN ceramics could be used for a wide range of application, such as integrated electro-optical devices

  11. Electrical properties of Li and Nd doped strontium bismuth titanate (SrBi4Ti4O15) ceramics

    International Nuclear Information System (INIS)

    Ceramic samples of Sr0.2Li0.4Nd0.4Bi4Ti4O15 (SLNBT) are prepared by high temperature solid state reaction method with a view to study their electrical properties by Complex Impedance Spectroscopy (CIS). Nyquist plots of Impedance and Electric Modulus in SLNBT ceramic suggest the relaxation to be non-Debye type. Peaks appear in Z versus frequency plots and they shift towards higher frequency side with increasing temperature. Similar behavior is observed in M versus frequency plots. The relaxation times are calculated from peak value of Z versus frequency and activation energies are evaluated. The AC conductivity measurements are recorded in a wide range of frequency and temperature. The activation energies for the ac conductivity are calculated. (author)

  12. Reversible magnetic properties of c-axis-oriented superconducting Bi2Sr2Ca2Cu3O10

    International Nuclear Information System (INIS)

    Magnetization measurements on c-axis-oriented bulk superconducting Bi2Sr2Ca2Cu3O10 have been carried out with the magnetic field applied parallel to the c axis. Fitting the results to the variation model for magnetization suggested by Hao and Clem shows that the Ginzburg-Landau parameter κ is nearly constant for 74≤T≤86 K, with the value of 170 at 74 K, and slowly increases with temperature from ∼86 to ∼100 K. κ diverges in the vicinity of Tc. This unusual temperature dependence of κ(T) could come from extended fluctuation effects and a limitation of the Hao-Clem theory, which may fail to describe this extremely anisotropic Bi-based superconductor. By fitting the data with the value of κ equal to 170, the deduced values of some of the superconducting parameters are Hc(0)=10 600 Oe, ξ(0)ab=10.5±0.6 A, λ(0)ab=1940±13 A, dHc2/dT congruent -3.68 T/K near Tc

  13. Bright upconversion luminescence and increased Tc in CaBi2Ta2O9:Er high temperature piezoelectric ceramics

    International Nuclear Information System (INIS)

    Er3+ doped CaBi2Ta2O9 (CBT) bismuth layered-structure high temperature piezoelectric ceramics were synthesized by the traditional solid state method. The upconversion (UC) emission properties of Er3+ doped CBT ceramics were investigated as a function of Er3+ 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 4S3/2 and 4F9/2 to 4I15/2, 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.

  14. 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.

  15. Nanomechanical behavior of 3D porous metal–ceramic nanocomposite Bi/Bi2O3 films

    International Nuclear Information System (INIS)

    The nanomechanical properties of three-dimensional (3D) porous metal/metal oxide composite (Bi/Bi2O3) 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-Bi2O3, 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

  16. 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

  17. Structure and superconductivity of sputtered Bi-Sr-Ca-Cu-O films from various targets

    International Nuclear Information System (INIS)

    Bi-Sr-Ca-Cu-O films were prepared by use of the single-target sputtering method: deposited on [100] MgO substrates and then annealed at 860degC. Targets of three types were used: 1) mixed powder of, 2) calcined powder of, 3) a sintered disk of Bi2O3, SrCO3, CaCO3 and CuO. Films made from the type 1) target almost peeled off from the substrate during the annealing, and small residual films consisted of c-axis-oriented phases of Bi2Sr2Ca1Cu2Ox (2212), Bi2Sr2Ca0Cu1Ox (2201) and a slight amount of Bi2Sr2Ca2Cu3Ox (2223). The films from the type 2) and 3) targets did not peel off and consisted of randomly oriented 2212 and 2201 phases. (author)

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

    Science.gov (United States)

    Arnold, Donna C

    2015-01-01

    Bismuth ferrite suffers from high leakage currents and the presence of a complex incommensurate spin cycloidal magnetic ordering, which has limited its commercial viability and has led researchers to investigate the functionality of doped BiFeO3 ceramics. In particular, the substitution of rare earths onto the Bi(3+) site of the perovskite lattice have been shown to lead to improved functional properties, including lower leakage currents and the suppression of the magnetic spin cycloid. There is particular interest in materials with compositions close to structural morphotropic phase boundaries, because these may lead to materials with enhanced electronic and magnetic properties analogous to the highly relevant PbZrO3- PbTiO3 solid solution. However, many contradictory crystal structures and physical behaviors are reported within the literature. To understand the structure-property relationships in these materials, it is vital that we first unravel the complex structural phase diagrams. We report here a comprehensive review of structural phase transitions in rare-earth-doped bismuth ferrite ceramics across the entire lanthanide series. We attempt to rationalize the literature in terms of the perovskite tool kit and propose an updated phase diagram based on an interpretation of the literature. PMID:25585391

  19. 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)

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

    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. (paper)

  2. 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.

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

    Science.gov (United States)

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

    2016-06-01

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

  4. 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)

  5. 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

  6. 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)

  7. 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...

  8. Vortex-pair excitation near the superconducting transition of Bi2Sr2CaCu2O8 crystals

    International Nuclear Information System (INIS)

    The dissipation observed at the superconducting transition of the high-T/sub c/ superconductor Bi2Sr2CaCu2O8 is explained quantitatively by the Kosterlitz-Thouless theory of vortex-antivortex pair excitations within the CuO2 planes. This conclusion is drawn from the observation of an exponential square-root singularity in the resistivity and a power-law dependence of the resistivity on magnetic field. The Kosterlitz-Thouless phase transition (T/sub c/ = 84.7 K) is at the rho = 0 point, and the mean-field Ginzburg-Landau tansition (T/sub c/0 = 86.8 K) is at∼25% of the normal-state resistivity

  9. 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.

  10. 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...

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. 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 ...

  18. Sintering, microstructure and electrical properties of 0.4(Bi0.5K0.5)TiO3-0.6BiFeO3 lead-free piezoelectric ceramics

    Science.gov (United States)

    Fisher, John G.; Park, Ha-Young; Song, Yeo-Ok; Baek, Sun-Joong; Vu, Hung; Kim, Jee-Hoon; Kim, Young-Hun; Lee, Jong Sook

    2016-01-01

    The effect of sintering temperature on the densification, microstructure and structure of 0.4(Bi0.5K0.5)TiO3-0.6BiFeO3 lead-free piezoelectric ceramics is assessed. The 0.4(Bi0.5K0.5)TiO3-0.6BiFeO3 powders were prepared by using the mixed-oxide method and were sintered at temperatures of 1000, 1050 and 1100 °C for 1 to 5 hrs. Unlike earlier work, the sintered samples showed high densities even when sintered at 1000 °C. X-ray diffraction revealed that the sintered samples shared the same rhombohedral structure as BiFeO3. With increasing sintering temperature, the rhombohedral distortion of the unit cell decreased. In addition to the relaxor-like broad peak around 400 °C, a low-temperature dielectric peak was found at temperatures below 190 °C by employing a low-frequency sweep down to 10 mHz. The DC conductivity of the 0.4(Bi0.5K0.5)TiO3-0.6BiFeO3 sample exhibited three temperature regions with activation energy values of 0.56 eV (T > 500°C), 0.72 eV (400°C BiFeO3.

  19. 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.

  20. Structure evolution and piezoelectric properties across the morphotropic phase boundary of Sm-substituted BiFeO3 ceramics

    Science.gov (United States)

    Shi, Xin Xin; Liu, Xiao Qiang; Chen, Xiang Ming

    2016-02-01

    The evolution of structure, ferroelectric, and piezoelectric properties in Bi1-xSmxFe0.99Ti0.01O3 ceramics was extensively investigated within the entire morphotropic phase boundary region with 0 ≤ x ≤ 0.20. A sequential phase transition of R3c-Pna21-Pbnm with increasing Sm content was revealed by Rietveld refinement of the X-ray diffraction data together with the macroscopic ferroelectric measurements. Both ferroelectric and piezoelectric properties showed a great enhancement in the vicinity of the R3c/Pna21 (polar-to-polar) phase boundary, which should be caused by the field-induced phase transition between these two phases. Such field-induced phase transition might be essentially accompanied by a change of magnetic state, which indicated a way of controlling magnetism by means of electric field.

  1. Microstructure of laser floating zone (LFZ) textured (Bi,Pb)-Sr-Ca-Cu-O superconductor composites

    International Nuclear Information System (INIS)

    Directionally solidified high temperature superconducting (Bi,Pb)-Sr-Ca-Cu-O pure ceramics and composites were obtained using a laser floating zone (LFZ) apparatus. The presence of secondary non-superconducting and metallic phases as well as their solidification habit have been analysed. The influence of the LFZ growth conditions and the precursor composition on the microstructure of the final products was studied using optical and electron microscopies. (orig.)

  2. 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...

  3. 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

  4. Resistive switching and threshold switching behaviors in La0.1Bi0.9Fe1-xCoxO3 ceramics

    International Nuclear Information System (INIS)

    The effects of cobalt doping on the electrical conductivity of La0.1Bi0.9Fe1-xCoxO3 (LBFCO, x = 0, 0.01, 0.03) ceramics were investigated. It is found that the leakage current increases with cobalt dopant concentration in LBFCO. On the application of bias voltage LBFCO ceramics with cobalt doping exhibits resistive switching effects at room temperature and threshold switching effects at elevated temperatures (50 °C and 80 °C). X-ray photoelectron spectroscopy of LBFCO ceramics show that cobalt dopant is bivalent as an acceptor, which induces an enhancement of oxygen vacancy concentration in LBFCO ceramics. Possible mechanisms for both resistive switching and threshold switching effects are discussed on the basis of the interplay of bound ferroelectric charges and mobile charged defects.

  5. Structural, Optical, and Electrical Characterization of Yttrium-Substituted BiFeO3 Ceramics Prepared by Mechanical Activation.

    Science.gov (United States)

    Perejón, Antonio; Gil-González, Eva; Sánchez-Jiménez, Pedro E; Criado, José M; Pérez-Maqueda, Luis A

    2015-10-19

    Ceramics of Bi(1-x)Y(x)FeO3 solid solutions (x = 0.02, 0.07, and 0.10) have been prepared by mechanical activation followed by sintering. The effect of yttrium content on the structural, electrical, and optical properties of the materials has been studied. Thus, single-phase solid solutions with rhombohedral R3c structure have been achieved for x = 0.02 and 0.07, while for x = 0.10 the main R3c phase has been detected together with a small amount of the orthorhombic Pbnm phase. Multiferroic properties of the samples, studied by differential scanning calorimetry (DSC), showed that both T(N) and T(C) (temperatures of the antiferromagnetic-paramagnetic and ferroelectric-paraelectric transitions, respectively) decrease with increasing yttrium content. The nature of the ferroelectric-paraelectric transition has been studied by temperature-dependent X-ray diffraction (XRD), which revealed rhombohedral R3c to orthorhombic Pbnm phase transitions for x = 0.07 and 0.10. On the other hand, for x = 0.02 the high-temperature phase was indexed as Pnma. Optical properties of the samples, as studied by diffuse reflectance spectroscopy, showed low optical band gap that decreases with increasing yttrium content. Prepared ceramics were highly insulating at room temperature and electrically homogeneous, as assayed by impedance spectroscopy, and the conductivity increased with x. PMID:26430852

  6. Structural and dielectric properties of lead free Bi0.5Na0.5TiO3 ceramics

    Science.gov (United States)

    Pattipaka, Srinivas; Mahesh, P.; Pamu, D.

    2016-05-01

    The lead free Bi0.5Na0.5TiO3 (BNT) ceramics were synthesized by using a solid state reaction method. The effect of sintering temperature on structure and dielectric properties of BNT ceramics studied systematically. It was observed that the samples calcined at 800 °C and sintered at 1100 °C shown the maximum density (5.67 g/cm3), with larger crystallite size (52 nm), high dielectric constant (ɛr = 694 at 1 kHz), and low dielectric loss (tanδ = 0.103). The XRD pattern reveals that rhombohedral phase with R3c space group at room temperature. The temperature dependent ɛr and tanδ displayed the two phase transitions including ferroelectric to anti-ferroelectric low phase transition (198 °C) and anti-ferroelectric to para electric phase transition (330 °C). The high frequency dielectric analysis revealed that weak relaxor behaviour presented in the system.

  7. 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.

  8. 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.

  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

    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+.

  10. 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+.

  11. Production of high-TC superconducting electric motor rotor elements by means of forming of superconducting junctions between blocks of melted textured ceramics on the base of YBa2Cu3O7-δ

    International Nuclear Information System (INIS)

    On basis of investigation of junctions forming between blocks of melted textured ceramics (MT-YBaCuO) and integrated study of structure, superconducting and mechanical properties of basic materials and patterns with junctions, a method of production of superconducting junctions with standard property level (critical current density in juncture area more than 10 kA/cm2 under 77 K in magnetic fields with strength up to 1,8 T, microhardness Hv=4,6 GPa under load of 1,96 N and flexural strength 28-32 MPa, thermal resistance coming to 150-200 cycles) was worked out

  12. 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.

  13. 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

  14. Electric field induced lattice strain in pseudocubic Bi(Mg1/2Ti1/2)O3-modified BaTiO3-BiFeO3 piezoelectric ceramics

    Science.gov (United States)

    Fujii, Ichiro; Iizuka, Ryo; Nakahira, Yuki; Sunada, Yuya; Ueno, Shintaro; Nakashima, Kouichi; Magome, Eisuke; Moriyoshi, Chikako; Kuroiwa, Yoshihiro; Wada, Satoshi

    2016-04-01

    Contributions to the piezoelectric response in pseudocubic 0.3BaTiO3-0.1Bi(Mg1/2Ti1/2)O3-0.6BiFeO3 ceramics were investigated by synchrotron X-ray diffraction under electric fields. All of the lattice strain determined from the 110, 111, and 200 pseudocubic diffraction peaks showed similar lattice strain hysteresis that was comparable to the bulk butterfly-like strain curve. It was suggested that the hysteresis of the lattice strain and the lack of anisotropy were related to the complex domain structure and the phase boundary composition.

  15. Dopant effects on the superconductivity of YBa2Cu3O7 ceramics

    International Nuclear Information System (INIS)

    We investigated the effects of SrTiO3 and 17 different oxide dopants, namely Ca, Sc, La, and Zr with possible substitution in the yttrium sites, K, Sr, and Pb in the barium sites, Li, Mg, Fe, Co, Ni, Zn, Al, Ti, Nb, and Si in the copper sites on the superconductivity of YBa2Cu3O7. These dopants can be classified into four categories depending on their solubilities and substitution in the different cation sublattices of YBa2Cu3O7 perovskite. Dopants in the first category dissolve and substitute in the copper sublattice and they can significantly reduce the transition temperature of the superconductivity of YBa2Cu3O7. For example, three dopants in this category, namely Zn, Mg, and Li, at 2 mole % dopant level, reduce the transition temperatures to 66, 65, and 82 K, respectively. The second category dopants substitute in the barium and yttrium sites, and these dopants, e.g., Sr at 2 mole % concentration, do not have any significant effect on the transition temperature of the superconductivity of YBa2Cu3O7. While dopants, e.g., AlO/sub 1.5/ and SiO2, in the third category have a limited solubility in YBa2Cu3O7, they have a strong tendency to decompose the superconducting phase by leaching out some components of YBa2Cu3O7. The transition temperature of the undecomposed superconducting phase remains unaffected at ∼91 K even though the susceptibility signal is reduced substantially. Since the dopants in the fourth category have a limited solubility and very little reactivity with YBa2Cu3O7, they are present simply as an inert second phase among the superconducting matrix

  16. Phase Structure, Piezoelectric and Multiferroic Properties of SmCoO3-Modified BiFeO3-BaTiO3 Lead-Free Ceramics

    Science.gov (United States)

    Jiang, Na; Tian, Mijie; Luo, Lingling; Zheng, Qiaoji; Shi, Dongliang; Lam, Kwok Ho; Xu, Chenggang; Lin, Dunmin

    2016-01-01

    (0.75- x)BiFeO3-0.25BaTiO3- xSmCoO3 + 1 mol.% MnO2 lead-free multiferroic ceramics were synthesized by a conventional ceramic fabrication technique. The effects of SmCoO3 on phase structure, piezoelectricity and multiferroicity of the ceramics were studied. All the ceramics can be well sintered at a low sintering temperature of 960°C. The crystalline structure of the ceramics is transformed from rhombohedral to tetragonal symmetry with increasing the amount of SmCoO3. A morphotropic phase boundary of rhombohedral and tetragonal phases is formed at x = 0.01-0.04. A small amount of SmCoO3 is shown to improve the ferroelectric, piezoelectric and magnetoelectric properties of the ceramics. For the ceramics with x = 0.01-0.03, enhanced resistivity ( R ˜ 1.2 × 109 Ω cm to 2.1 × 109 Ω cm), piezoelectricity ( d 33 ˜ 65 pC/N to 106 pC/N) and ferroelectricity ( P r ˜ 6.38 μC/cm2 to 22.89 μC/cm2) are obtained. The ferromagnetism of the materials is greatly enhanced by the doping of SmCoO3 such that a very high magnetoelectric coefficient of ˜742 mV/(cm Oe) is obtained at x = 0.01, suggesting a promising potential in multiferroic devices.

  17. Sintering Processing and Piezoelectric Properties of K0.5Na0.5NbO3-BiFeO3 Lead-free Ceramics

    Directory of Open Access Journals (Sweden)

    JIANG Min-Hong,CHEN He-Xin,LIU Xin-Yu,YANG Li-Qing,ZHOU Chang-Rong

    2009-11-01

    Full Text Available Leadª²free BiFeO3 (BF doped K0.5Na0.5NbO3 (KNN piezoelectric ceramics were prepared by a traditional ceramic processing. The effects of sintering temperature and holding time on the microstructure, phase transition, density and piezoelectric properties of BF doped KNN ceramics were investigated. The results show that all specimens exhibit a pure perovskite structure. The surface micrograph, density and piezoelectric properties of the ceramics depend strongly on the sintering temperature and holding time. When being sintered at temperature from 1100¡䟴o 1150¡䟦or 3h, the d33, Kp and Qm of the ceramics increase, while the tan¦ decreases with the sintering temperature increasing. When being sintered at 1150¡䟦or 1h to 3h, the d33, Kp and Qm of the ceramics increase firstly and then remain unchanged, while the tan¦ decreases firstly and then also remains unchanged with the holding time increasing. The BFª²doped KNN ceramics sintered at 1150¡䟦or 2h exhibit excellent properties (¦ϼ/EM>=4.50g/cm3£¬ d33=132pC/N, Kp=45%, Qm=333.73, tan¦¼/EM>=2.39%.

  18. 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.

  19. 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)

  20. 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.

  1. Anisotropy in vortex pinning and superconductivity of Bi1.5Pb0.7Sr1.8CaCu2O8+δ single crystal

    International Nuclear Information System (INIS)

    The Bi2Sr2CaCu2O8 crystal is a representative of the two-dimensional high-Tc superconductivity (γc - 200) while the superconductivity achieved in YBa2Cu3O7 is of rather three-dimensional nature (γc - 8). Consequently, the vortex pinning in Bi2Sr2CaCu2O8 is not so strong at higher temperatures. Single crystals of Bi2.2-xPbxSr1.8CaCu2O8+δ grown by a floating zone method showed a dramatic high Jc compared to a lead-free single crystal. This finding is extremely encouraging for potential applications. One of the possible origins for the high Jc is the enhanced dimensionality of the superconductivity in a lead-doped system. The Bi2.2-xPbxSr1.8CaCu2O8+δ crystal is also characterized by the lamella structure between the Pb-rich and Pb-poor phases. It is known that twin boundaries in YBa2Cu3O7 act as strong directional pinning centers and accommodate the lock-in vortices at higher temperatures. The torque is a sensitive tool for various anisotropic properties and has widely been used to investigate a high-Tc cuprate. In this work, we apply this technique to the Bi2.2-xPbxSr1.8CaCu2O8+δ crystal. (author)

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

    DEFF Research Database (Denmark)

    Chen, X.P.; Grivel, Jean-Claude; Li, M.Y.; Liu, Q.; Han, Z.; Andersen, Niels Hessel; Homeyer, J.

    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...

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

    Directory of Open Access Journals (Sweden)

    John G. Fisher

    2015-12-01

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

  4. Mechanical properties of Ag-clad Bi-based superconducting composite tapes

    International Nuclear Information System (INIS)

    The critical strains for tensile and bend tests show a dependence on the tape thickness and Ag/oxide volume ratio. This is attributable to the improved strength and flexibility of the special interfacial layer between Ag and oxides formed during thermomechanical processes. Microstructure studies reveal that at a strain greater than the critical strain, there are cracks in the oxide core, while the interfacial layer near the Ag sheath is still intact. Multifilamentary configuration is desirable for improving the strength and flexibility of the Ag-clad Bi-based tapes. (orig.)

  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. 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

  7. Irreversibility behavior in Ag-sheathed Bi-based superconducting wires

    Energy Technology Data Exchange (ETDEWEB)

    Dou, S.X.; Liu, H.K.; Guo, Y.C.; Wang, J.; Jin, X.J.; Hu, Q.Y. (New South Wales Univ., Kensington (Australia)); Shi, D.L.; Salem-Sugui, S.; Wang, Z. (Argonne National Lab., IL (United States))

    1992-04-01

    Irreversibility lines for Ag/(Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub y}(2223) wires prepared through a phase formation- decomposition-recovery (PFDR) process and normal annealing process were determined using both AC susceptibility measurements under DC fields and magnetisation measurements. It was found that flux pinning was enhanced in the PFDR processed samples over the normal processed samples, in particular at temperature above 77 K. The PFDR process results in high mass density, grain alignment, uniform distribution of impurity precipitates and high density of defects. The irreversibility temperatures scaled with the applied field according to H{sup 1/3}, which is in contrast to H{sup 2/3} law for YBa{sub 2}Cu{sub 3}O{sub 7-x} and conventional superconductors. The irreversibility lines for PFDR processed tapes showed a crossover with those for normal processed tapes at temperature below {Tc} of the (Bi,Pb){sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+x} (2212), suggesting that at temperature above {Tc} of the 2212 phase, the 2212 as nonsuperconducting region, may serve as effective pinning sites for fluxoids.

  8. Irreversibility behavior in Ag-sheathed Bi-based superconducting wires

    Science.gov (United States)

    Dou, S. X.; Liu, H. K.; Guo, Y. C.; Wang, J.; Jin, X. J.; Hu, Q. Y.; Shi, D. L.; Salem-Sugui, S.; Wang, Z.

    1992-04-01

    Irreversibility lines for Ag/(Bi,Pb)2Sr2Ca2Cu3O(y)(2223) wires prepared through a phase formation- decomposition-recovery (PFDR) process and normal annealing process were determined using both AC susceptibility measurements under DC fields and magnetization measurements. It was found that flux pinning was enhanced in the PFDR processed samples over the normal processed samples, in particular at temperatures above 77 K. The PFDR process results in high mass density, grain alignment, uniform distribution of impurity precipitates, and high density of defects. The irreversibility temperatures scaled with the applied field according to H(sup 1/3), which is in contrast to H(sup 2/3) law for YBa2Cu3O(7-x) and conventional superconductors. The irreversibility lines for PFDR processed tapes showed a crossover with those for normal processed tapes at temperatures below T(sub c) of the (Bi,Pb)2Sr2CaCu2O(8+x) (2212), suggesting that at temperatures above T(sub c) of the 2212 phase, the 2212 as a nonsuperconducting region, may serve as effective pinning sites for fluxoids.

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

    Directory of Open Access Journals (Sweden)

    Mostafavi E.

    2016-03-01

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

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

    International Nuclear Information System (INIS)

    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

  11. 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

  12. 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.

  13. 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

  14. 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.

  15. 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)

  16. First principles study of the spin-orbit coupling effect on the Tl-Pb-Bi superconducting alloys

    Energy Technology Data Exchange (ETDEWEB)

    Pena-Seaman, Omar de la; Heid, Rolf; Bohnen, Klaus-Peter [Karlsruher Institut fuer Technologie (KIT), Institut fuer Festkoerperphysik (Germany)

    2011-07-01

    We have studied the influence of spin-orbit coupling (SOC) on the phonon properties, the electron-phonon (e-ph) coupling and on the superconducting properties for the Pb-Bi and Pb-Tl alloys in the stable fcc-phase doping regimes. These systems have been studied within the framework of density functional perturbation theory, using a mixed-basis pseudopotential method and the virtual crystal approximation (VCA) for modeling the alloys. The Eliashberg spectral function ({alpha}{sup 2}F({omega})) and the electron-phonon coupling parameter ({lambda}) have been calculated with and without SOC. The observed effects of SOC in the full phonon dispersion and {alpha}{sup 2}F({omega}) consist in a softening of the phonon frequencies and an increase of the e-ph coupling matrix elements, which become weaker on the Tl-rich side. SOC enhances {lambda} by as much as 48% in some cases and improves its overall behavior as a function of the concentrations for the alloy systems, leading to a very nice agreement with experimental data from tunneling measurements.

  17. 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)

  18. Role of weakly bound oxygen in the exoemission and superconductivity of YBa2Cu3O(7-x) high-temperature superconductor ceramic

    Science.gov (United States)

    Krylova, I. V.; Makarov, A. V.

    1991-12-01

    Experiments were carried out on a high-temperature superconductor ceramic, YBa2Cu3o(6.86), to determine the effect of various forms of sorbed oxygen on superconductivity and formation of the surface localization levels of electrons that determine exoemission. Results of the high-temperature mass spectrometry of thermal oxygen desoprtion, thermally stimulated exoemission in the temperature range 293-700 K, and exoemission parameters in the low-temperature regions (293-77 K) are compared.

  19. 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

  20. 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

  1. Pinning and vortex dynamics in superconducting ( K, Ba) BiO 3 single crystals

    Science.gov (United States)

    Klein, T.; Harneit, W.; Baril, L.; Escribe-Filippini, C.

    1996-11-01

    Pinning and vortex dynamics have been investigated in the 3-dimensional copper free (K, Ba)BiO3superconductor (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). We 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.

  2. Reversible effect of strain on transport critical current in Bi2Sr2CaCu2O8 + x superconducting wires: a modified descriptive strain model

    Science.gov (United States)

    Cheggour, N.; Lu, X. F.; Holesinger, T. G.; Stauffer, T. C.; Jiang, J.; Goodrich, L. F.

    2012-01-01

    A reversible strain effect on transport critical current Ic was found in Bi2Sr2CaCu2O8 + x (Bi-2212) high-temperature superconducting round wires. Ic showed unambiguous reversibility at 4 K and 16 T up to an irreversible strain limit of about 0.3 % in longitudinal tension, prompting hope that the Bi-2212 conductor has the potential to sustain mechanical strains generated in high-field magnets. However, Ic was not reversible under longitudinal compression and buckling of Bi-2212 grain colonies was identified as the main reason. A two-component model was proposed, which suggests the presence of mechanically weak and strong Bi-2212 components within the wire filaments. Porosity embedded in the weak component renders it structurally unsupported and, therefore, makes it prone to cracking under strain ɛ. Ic(ɛ) is irreversible in tension if the weak component contributes to the transport critical current but becomes reversible once connectivity of the weak component is broken through strain increase or cycling. A modified descriptive strain model was also developed, which illustrates the effect of strain in the Bi-2212 conductor and supersedes the existing descriptive model. Unlike the latter, the new model suggests that higher pre-compressive strains should improve Ic if buckling of Bi-2212 grains does not occur, and should result in a wider Ic(ɛ) plateau in the applied tensile regime without degradation of the initial Ic. The new model postulates that a reversible strain effect should exist even in the applied compressive strain regime if buckling of Bi-2212 grains could be prevented through elimination of porosity and mechanical reinforcement of the wire. Contribution of NIST, an agency of the US government, not subjected to copyright.

  3. Reversible effect of strain on transport critical current in Bi2Sr2CaCu2O8+x superconducting wires: a modified descriptive strain model

    International Nuclear Information System (INIS)

    A reversible strain effect on transport critical current Ic was found in Bi2Sr2CaCu2O8+x (Bi-2212) high-temperature superconducting round wires. Ic showed unambiguous reversibility at 4 K and 16 T up to an irreversible strain limit of about 0.3 % in longitudinal tension, prompting hope that the Bi-2212 conductor has the potential to sustain mechanical strains generated in high-field magnets. However, Ic was not reversible under longitudinal compression and buckling of Bi-2212 grain colonies was identified as the main reason. A two-component model was proposed, which suggests the presence of mechanically weak and strong Bi-2212 components within the wire filaments. Porosity embedded in the weak component renders it structurally unsupported and, therefore, makes it prone to cracking under strain ε. Ic(ε) is irreversible in tension if the weak component contributes to the transport critical current but becomes reversible once connectivity of the weak component is broken through strain increase or cycling. A modified descriptive strain model was also developed, which illustrates the effect of strain in the Bi-2212 conductor and supersedes the existing descriptive model. Unlike the latter, the new model suggests that higher pre-compressive strains should improve Ic if buckling of Bi-2212 grains does not occur, and should result in a wider Ic(ε) plateau in the applied tensile regime without degradation of the initial Ic. The new model postulates that a reversible strain effect should exist even in the applied compressive strain regime if buckling of Bi-2212 grains could be prevented through elimination of porosity and mechanical reinforcement of the wire.

  4. Exoemission of charged particles from the surface of irradiated high-temperature superconducting ceramics

    International Nuclear Information System (INIS)

    The present communication reports the results of the study of the samples of YBa2Cu3O7 ceramics with a density of 5.4 g/cm3, composed of one phase with Tc = 92 K in the form of 1 mm thick tablets 10 mm in diameter. Part of the samples was obtained in the air by the use of gamma-quanta (Cobalt-60), the absorbed dose was 106 rad. The design of the facility for recording the thermostimulated exoemission (TSE) spectra of positive and negative particles allowed the measurements to be made in the vacuum of 10-8 Tor at a heating rate of 0.1 K [4]. Part of the experiments was made using non-irradiated ceramics which were spalled in a vacuum chamber shortly before recording the TSE spectra

  5. Preparation and characterization of textured high-Tc superconducting ceramics by creep-sintering

    International Nuclear Information System (INIS)

    The possibility of texturing high-Tc ceramics by sintering them under a uniaxial stress was investigated in detail. It is shown that texturing is very sensitive not only to the temperature and the load used to sinter the specimens, but also to the rate at which this temperature and this load are reached, and to the composition and thickness of the metallic foils in contact with the ceramic. The investigation puts in evidence a very strong correlation between the degree of texturing achieved and the deformation rate of the sample. Silver addition was found to have no beneficial effect neither on improving texturing nor on re-oxygenation, it just hardens the material which, for a given load, lowers the deformation rate and consequently the degree of texturing. Microstructural, electrical and magnetic characterizations of various samples are presented, and it is concluded that the critical current density in our samples is still limited by grain boundary and re-oxygenation problems

  6. Piezoelectric Properties of Pb0.98Bi0.02Zr0.51Ti0.48Zn0.01O3 Ceramics

    Science.gov (United States)

    He, Wenze; Yu, Jian

    2011-02-01

    On the basis of eutectic behavior of PbTiO3-PbZrO3-Bi(Zn0.5Ti0.5)O3 ternary system, perovskite-structured Pb0.98Bi0.02Zr0.51Ti0.48Zn0.01O3 ceramics were able to be prepared using conventional electronic ceramic processing at low sintering temperature compatible with Ag as inner electrode materials, promising for co-firing technology to fabricate monolithic multilayer piezoelectric transducers. The dependence of its piezoelectric properties on sintering temperature and various dopants were investigated experimentally and a piezoelectric property with dielectric constant of ɛ33T/ɛ0=1190, dielectric loss of tan δ=0.6%, piezoelectric coefficient of d33=270 pC/N, planar coupling coefficient of kp=0.54, thickness coupling coefficient of kt=0.46 and Curie temperature of Tc=346 °C was obtained for the 0.5% Co-doped Pb0.98Bi0.02Zr0.51Ti0.48Zn0.01O3 ceramics sintered at 950 °C.

  7. 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.

  8. 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.

  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. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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.

    2016-04-01

    (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.

  16. The effect of Bi2 O3 on the electrical properties of Zr O2:3 wt% Mg O ceramic solid electrolytes

    International Nuclear Information System (INIS)

    Electrical conductivity measurements have been carried out in the 4000 C-7000 C temperature range in Zr Oz:3 wt% Mg O ceramic solid electrolytes with 5 wt% Bi2 Os additions. All specimens were prepared by pressing followed by thermal treatments at 8000 C/1 h and 11500 C/3 h. Microstructural characterization have been done by X-ray diffractometry, scanning electron microscopy and electron microprobe analyses. The results show that 5 wt% Bi2 O3 addition improves densification: 93% TD and 98% TD specimens are obtained from zirconia stabilized by powder mixture and by coprecipitation of oxides, respectively. Moreover, electrical conductivity values are found to be two orders of magnitude higher for Zr O2:3 wt% Mg O with 5 wt% Bi2 O3 addition. (author)

  17. The effect of Bi2 O3 on the electrical properties of Zr O2: 3 wt% Mg O ceramic solid electrolytes

    International Nuclear Information System (INIS)

    Zr O2: 3 wt% Mg O ceramic solid electrolytes have been prepared to study the effect of Bi2 O3 addition on densification and electrical conductivity. Microstructural characterization have been done by X-ray diffractometry, scanning electron microscopy and electron microprobe analyses. Electrical conductivity measurements have been done by two probe dc technique in the 4000 C - 7000 C temperature range. The results show that 5 wt% Bi2 O3 addition improves densification: 93% TD and 98% TD specimens are obtained from zirconia stabilized by powder mixture and by coprecipitation of oxides, respectively. Moreover, electrical conductivity values are found to be two orders of magnitude higher for Zr O2 : 3 wt% Mg O with 5% Bi2 O3. (author)

  18. Effect of Al3+ substitution on the structural, magnetic, and electric properties in multiferroic Bi2Fe4O9 ceramics

    International Nuclear Information System (INIS)

    Structural, magnetic, and electric properties have been investigated in polycrystalline Bi2(Fe1−xAlx)4O9 (0≤x≤0.25) ceramics synthesized by a modified Pechini method. Structural analysis reveals that Al3+ doped Bi2Fe4O9 crystallizes in orthorhombic structure with Pbnm space group. Surface morphology of the end products is examined by scanning electron microscopy and the grain size has a tendency to decrease with increase in Al3+ doping level. Compared with pure Bi2Fe4O9, room temperature coexistent multiferroic-like behavior is observed in Al3+ doped Bi2Fe4O9. By analyzing magnetic properties, the Néel temperature monotonously shifts to low temperatures from ~260 K (x=0) to ~35 K (x=0.25). Moreover, the spin dynamic measured by the shift in ac magnetic susceptibility as a function of frequency provides a possibility of spin-glass-like behavior, which is further confirmed by fitting the critical slowing down power law and memory effect. - Graphical abstract: Compared with pure Bi2Fe4O9, room temperature weak ferromagnetic property and enhanced ferroelectric-like behavior can be achieved simultaneously with proper Al3+ doping. - Highlights: • Bi2(Fe1−xAlx)4O9 (0≤x≤0.25) ceramics are fabricated via a Pechini method. • Weak ferromagnetic and ferroelectric behaviors can be achieved simultaneously. • Spin-glass-like behavior is detected with proper Al3+ doping. • The memory and aging effects are observed with proper Al3+ doping

  19. Design, fabrication and characterization of a low-temperature co-fired ceramic gaseous bi-propellant microthruster

    International Nuclear Information System (INIS)

    A gaseous bi-propellant chemical microthruster was developed using low-temperature co-fired ceramic (LTCC) tapes. A sapphire window and silver spark ignition electrodes were successfully co-fired in the LTCC microthruster. Thrust outputs between 0.2 mN and 1.97 mN could be achieved from the 9.9 mm3 thrust chamber by hot-gas operation using ethylene–argon/oxygen mixtures. A non-premixed combustion scheme was utilized by applying an inlet configuration with offset opposing fuel and oxidizer ports. The inlet port design was able to facilitate the generation of swirling flow. Fuel/oxidant mixing could be enhanced in the thrust chamber with the swirling streams according to the cold-flow multi-species 3D computational fluid dynamics (CFD) analysis. Flame chemiluminescence measurements through the transparent observation window were performed to characterize the flame structure in the miniature combustion chamber. The flame zone was found to coincide with the stoichiometric plane predicted by the CFD simulations. Thrust measurements were accomplished by measuring the impingement force of the exhaust jet on a precision balance. The disturbance introduced by the tubing and wiring on the continuous flow microthruster could therefore be eliminated. Thrust was linearly proportional to the total mass flow rate of the inlet. The chemical energy input of the microthruster was approximately 37 W for the maximal measured thrust of 1.97 mN.

  20. Structural, thermal, electrical and magnetic properties of pure and 50% La doped BiFeO3 ceramics

    Science.gov (United States)

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

    2012-09-01

    Polycrystalline ceramic samples of pure and 50% La substituted BiFeO3 have been prepared by standard solid state reaction method using high purity oxides and carbonates. The formation of the single phase compound as well as its chemical analysis has been checked by X-ray diffraction and energy dispersive X-ray microanalysis (EDAX) techniques. A better agreement between observed and calculated X-ray powder diffraction patterns was obtained by performing the Rietveld refinement with a structural model using the non-centrosymmetric space group R3c. The lattice parameters in both the cases have been refined but the over-all structure remains the same. The microstructural studies have been carried out using scanning electron microscopy (SEM). Modulated differential scanning calorimetry (MDSC) has been used to detect the Neel/transition temperature in the compounds. The activation energies calculated from log σ vs 1/T curve are 0.81 eV and 1.13 eV respectively. Vibrating sample magnetometer (VSM) has been used to study the magnetic behaviour of the compounds. It has been observed that by 50% La substitution the insulating behaviour of the material has been improved and showing the antiferromagnetic to weak ferromagnetic behaviour.

  1. Structural, thermal, electrical and magnetic properties of pure and 50% La doped BiFeO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Jangid, S.; Barbar, S.K.; Bala, Indu [Department of Physics, M.L. Sukhadia University, Durga Nursery Road, Udaipur, Rajasthan 313001 (India); Roy, M., E-mail: mroy1959@yahoo.co.in [Department of Physics, M.L. Sukhadia University, Durga Nursery Road, Udaipur, Rajasthan 313001 (India)

    2012-09-15

    Polycrystalline ceramic samples of pure and 50% La substituted BiFeO{sub 3} have been prepared by standard solid state reaction method using high purity oxides and carbonates. The formation of the single phase compound as well as its chemical analysis has been checked by X-ray diffraction and energy dispersive X-ray microanalysis (EDAX) techniques. A better agreement between observed and calculated X-ray powder diffraction patterns was obtained by performing the Rietveld refinement with a structural model using the non-centrosymmetric space group R3c. The lattice parameters in both the cases have been refined but the over-all structure remains the same. The microstructural studies have been carried out using scanning electron microscopy (SEM). Modulated differential scanning calorimetry (MDSC) has been used to detect the Neel/transition temperature in the compounds. The activation energies calculated from log {sigma} vs 1/T curve are 0.81 eV and 1.13 eV respectively. Vibrating sample magnetometer (VSM) has been used to study the magnetic behaviour of the compounds. It has been observed that by 50% La substitution the insulating behaviour of the material has been improved and showing the antiferromagnetic to weak ferromagnetic behaviour.

  2. Structural, thermal, electrical and magnetic properties of pure and 50% La doped BiFeO3 ceramics

    International Nuclear Information System (INIS)

    Polycrystalline ceramic samples of pure and 50% La substituted BiFeO3 have been prepared by standard solid state reaction method using high purity oxides and carbonates. The formation of the single phase compound as well as its chemical analysis has been checked by X-ray diffraction and energy dispersive X-ray microanalysis (EDAX) techniques. A better agreement between observed and calculated X-ray powder diffraction patterns was obtained by performing the Rietveld refinement with a structural model using the non-centrosymmetric space group R3c. The lattice parameters in both the cases have been refined but the over-all structure remains the same. The microstructural studies have been carried out using scanning electron microscopy (SEM). Modulated differential scanning calorimetry (MDSC) has been used to detect the Neel/transition temperature in the compounds. The activation energies calculated from log σ vs 1/T curve are 0.81 eV and 1.13 eV respectively. Vibrating sample magnetometer (VSM) has been used to study the magnetic behaviour of the compounds. It has been observed that by 50% La substitution the insulating behaviour of the material has been improved and showing the antiferromagnetic to weak ferromagnetic behaviour.

  3. 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

  4. Neutron tomography experiments for the study of trapped flux distributions in high-Tc superconducting ceramics

    International Nuclear Information System (INIS)

    We describe a new version of Neutron Spin Echo, for the study of magnetic flux in high-Tc superconductors, which is based on the evolution of the echo group in the specimen which is installed in the third precession region. The polarization of the transmitted beam reflects the spin rotation in the internal field which can be found by Fourier transforming the data. It is required for example, in research on the flux self-organization in the critical state. Experiments on Y-Ba-Cu-O ceramics are discussed. (orig.)

  5. Processes of hydration aging of superconducting ceramics and problem of regeneration of properties

    International Nuclear Information System (INIS)

    The process of hydration aging (distilled water, saturated water vapors) of YBa2Cu3O6.5+x specimens with Ts of about 95 K was studied at 55 deg C and water vapors pressure of 119 mmHg. It is established that depending on exposure time and saturated vapors pressure, water affects electric properties of yttrium-barium ceramics with different degree of the effect reversibility. Valuable regeneration of the characteristics can occur only when the hydration process has not led to changes in the phase composition of the material. The mechanism of interaction between cermaics and water is given

  6. Sintering characteristics of La/Nd doped Bi4Ti3O12 bismuth titanate ceramics

    Directory of Open Access Journals (Sweden)

    Islam Aminul Md.

    2015-01-01

    Full Text Available A good understanding about the properties of La/Nd doped Bismuth Titanate (BIT ceramics at high temperature is very important as the new materials being developed based on the BIT. Pure BIT, La doped (BLT, Nd doped (BNT and La and Nd co-doped BIT (BLNT powders were synthesized by solid state reaction method. Prepared powders were calcined at different temperatures and structural properties measured by XRD. For pure BIT better crystal quality was obtained at 750 0C and for both BLT and BNT better result obtained at 800 0C. Calcined powders were formed into pellets and sintered at different temperatures and its dielectric properties were characterized. Optimum sintering temperature for both BLT and BNT showed was 850 0C and La and Nd co-doped bismuth titanate (BLNT revealed optimum sintering temperature of 950 0C. Therefore, optimum sintering temperature of bismuth titanate was increased due to La and Nd doping.

  7. Piezoelectric and dielectric properties of cerium-modified Aurivillius type K0.5La0.5Bi4Ti4O15 ceramics

    International Nuclear Information System (INIS)

    The Aurivillius type potassium lanthanum bismuth titanate (K0.5La0.5Bi4Ti4O15, KLBT) polycrystalline ceramics with 0.0-1.0 wt.% CeO2 were synthesized using conventional solid-state processing. X-ray diffraction analysis revealed that the cerium-modified KLBT ceramics have a pure four-layer Aurivillius type structure. The effects of cerium oxide on the piezoelectric, ferroelectric and dielectric properties on the KLBT ceramics were investigated. By the cerium modification, the piezoelectric activities of KLBT ceramics were significantly improved and the dielectric loss decreased. The piezoelectric coefficient d33 for the 0.50 wt.% CeO2-modified KLBT was found to be 28 pC N-1, the highest value among the modified KLBT-based piezoceramics. The reason for piezoelectric activities enhancement with Ce modification was given. The dielectric spectroscopy presented that the Curie temperature for all the KLBT ceramics is higher than 400 deg. C

  8. Phase transition, microstructures and electromechanical properties of BiAlO3-modified Bi0.5(Na,K)0.5TiO3 lead-free piezoelectric ceramics

    International Nuclear Information System (INIS)

    Lead-free piezoelectric (1-x)(Bi0.5(Na0.75K0.25)0.5TiO3)-xBiAlO3 (BNKT25-BA, 0 ≤ x ≤ 0.10) ceramics were synthesized using a conventional solid state reaction method. The incorporation of BA into the BNKT25 lattice was investigated by using X-ray diffraction (XRD), ferroelectric characterizations and electric-field-induced strain behavior. X-ray diffraction revealed a pure perovskite phase for x ≤ 0.050. A phase transformation from tetragonal to pseudocubic was observed at x = 0.050. The polarization hysteresis loops of the BNTK25-BA ceramics indicate that the addition of BA significantly disrupts the ferroelectric order of BNKT25 ceramics. The destabilization of the ferroelectric order is accompanied by an enhancement of the unipolar strain. In particular, a large electric-field-induced strain (S = 0.29%) and a normalized strain (d*33 = Smax/Emax = 484 pm/V) were observed at x = 0.025, near the tetragonal-pseudocubic phase boundary. These results suggest that the BNKT25-BA system is a promising candidate for lead-free electromechanical applications.

  9. 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).

  10. Superconductivity

    International Nuclear Information System (INIS)

    Research on superconductivity at ENEA is mainly devoted to projects related to the ITER magnet system. In this framework, ENEA has been strongly involved in the design, manufacturing and test campaigns of the ITER toroidal field model coil (TFMC), which reached a world record in operating current (up to 80 kA). Further to this result, the activities in 2004 were devoted to optimising the ITER conductor performance. ENEA participated in the tasks launched by EFDA to define and produce industrial-scale advanced Nb3Sn strand to be used in manufacturing the ITER high-field central solenoid (CS) and toroidal field (TF) magnets. As well as contributing to the design of the new strand and the final conductor layout, ENEA will also perform characterisation tests, addressing in particular the influence of mechanical stress on the Nb3Sn performance. As a member of the international ITER-magnet testing group, ENEA plays a central role in the measurement campaigns and data analyses for each ITER-related conductor and coil. The next phase in the R and D of the ITER magnets will be their mechanical characterisation in order to define the fabrication route of the coils and structures. During 2004 the cryogenic measurement campaign on the Large Hadron Collider (LHC) by-pass diode stacks was completed. As the diode-test activity was the only LHC contract to be finished on schedule, the 'Centre Europeenne pour la Recherche Nucleaire' (CERN) asked ENEA to participate in an international tender for the cold check of the current leads for the LHC magnets. The contract was obtained, and during 2004, the experimental setup was designed and realised and the data acquisition system was developed. The measurement campaign was successfully started at the end of 2004 and will be completed in 2006

  11. Superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Batistoni, Paola; De Marco, Francesco; Pieroni, Leonardo (ed.)

    2005-07-01

    Research on superconductivity at ENEA is mainly devoted to projects related to the ITER magnet system. In this framework, ENEA has been strongly involved in the design, manufacturing and test campaigns of the ITER toroidal field model coil (TFMC), which reached a world record in operating current (up to 80 kA). Further to this result, the activities in 2004 were devoted to optimising the ITER conductor performance. ENEA participated in the tasks launched by EFDA to define and produce industrial-scale advanced Nb3Sn strand to be used in manufacturing the ITER high-field central solenoid (CS) and toroidal field (TF) magnets. As well as contributing to the design of the new strand and the final conductor layout, ENEA will also perform characterisation tests, addressing in particular the influence of mechanical stress on the Nb3Sn performance. As a member of the international ITER-magnet testing group, ENEA plays a central role in the measurement campaigns and data analyses for each ITER-related conductor and coil. The next phase in the R and D of the ITER magnets will be their mechanical characterisation in order to define the fabrication route of the coils and structures. During 2004 the cryogenic measurement campaign on the Large Hadron Collider (LHC) by-pass diode stacks was completed. As the diode-test activity was the only LHC contract to be finished on schedule, the 'Centre Europeenne pour la Recherche Nucleaire' (CERN) asked ENEA to participate in an international tender for the cold check of the current leads for the LHC magnets. The contract was obtained, and during 2004, the experimental setup was designed and realised and the data acquisition system was developed. The measurement campaign was successfully started at the end of 2004 and will be completed in 2006.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. Formation and properties of Bi-Sr-Ca-Cu-O/ZrO2/Si(Al2O3) high temperature superconductive films

    International Nuclear Information System (INIS)

    Films in Bi-Sr-Ca-Cu-O/ZrO2/Si(Al2O3), Bi-Sr-Ca-Cu-O/(ZrO2 + 10%Y2O5)/Si systems are produced, investigation into their composition and interaction between their components by the methods of X-ray electron spectrometry is conducted, resistance temperature progress is measured, superconducting transition temperature is determined. It is shown that films produced in the course of spray coating are characterized by a uniform distribution of film elements by depth, presence of a clear boundary between the film and sublayer and absence of mutual diffusion of film and substrate elements. The film annealing leads to a notable sublayer broadening, erosion of its boundaries and a partial penetration of film elements to the substrate. An increase of annealing time amplifies, and introduction of stabilizing Y2O3 additions weakens these processes

  17. 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...

  18. 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.

  19. Local structural excitations and critical temperature of supported superconducting oxides

    International Nuclear Information System (INIS)

    High resolution IR spectra for the following complex oxides: La2CuO4, Nd2CuO4, YBa2Cu3O7-x, BaBiO3, HgCaBaCuO (at cations ratio 1223) were obtained for studying the role of oxygen sublattice in formation of electrophysical properties of superconducting oxide ceramics. Frequencies of vibration spectra sensitive to lattice distortions, oxygen content and occurrence of its excited states, were revealed. The assumption on local structural excitations and role of donor-acceptor interactions in formation of high-temperature superconductivity was confirmed

  20. Effect of structural transition on magnetic and dielectric properties of La and Mn co-substituted BiFeO3 ceramics

    International Nuclear Information System (INIS)

    Bi1−xLaxFe1−xMnxO3 (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 (BiFeO3). It was found that the co-substitution of La and Mn at Bi and Fe sites leads to suppression of impurity phases (Bi2Fe4O9 and Bi25FeO40) which generally appear in BiFeO3. 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 BiFeO3 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 Bi0.950L0.050Fe0.950Mn0.050O3 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 suppressed for x > 0.025 of Bi1−xLaxFe1−xMnxO3. • Crystallographic phase transition from rhombohedral

  1. 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

  2. An investigation into texturing of high-Tc superconducting ceramics by creep-sintering

    International Nuclear Information System (INIS)

    The possibility of preparing highly textured samples of YBa2Cu3O7-x high-Tc ceramics by creep-sintering under an uniaxial stress was investigated in detail. It is shown that the quality of the texture is sharply dependant on: the applied load, the temperature of the sintering dwell, the rate at which this dwell is reached, the exact instant at which the load is applied and the nature of the material in contact with the sample. It is also shown that further annealing without applied stress enhances the texture and considerably increases the grain size. Deformation, which was systematically recorded, occurs within a few minutes after the load is applied and exhibits a stress dependance typical of a viscous flow. Systematic examination by polarized light microscopy has indicated that the texture was homogeneous throughout the whole thickness of all the prepared samples. The resistivity versus temperature curves show that the transition is very sharp and well above 77 K

  3. 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...

  4. Magnetic-field-modulated microwave-absorption detection in a Bi-Sr-Ca-Cu-O superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Bohandy, J.; Adrian, F.J.; Kim, B.F.; Moorjani, K.; Shull, R.D.; Swartzendruber, L.J.; Bennett, L.H.; Wallace, J.S.

    1988-06-01

    Superconducting transitions are observed at 110 K, 100 K, and 72 K in a nominally BiSrCaCu/sub 2/O/sub x/ ceramic using the novel technique of magnetic-field-modulated microwave-absorption detection. The response of the BiSrCaCu/sub 2/O/sub x/ ceramic to an external magnetic field differs markedly from that of YBa/sub 2/Cu/sub 3/O and, in particular, -dT/sub c//dH is much greater in the bismuth sample.

  5. Magnetic-field-modulated microwave-absorption detection in a Bi-Sr-Ca-Cu-O superconductor

    International Nuclear Information System (INIS)

    Superconducting transitions are observed at 110 K, 100 K, and 72 K in a nominally BiSrCaCu2O/sub x/ ceramic using the novel technique of magnetic-field-modulated microwave-absorption detection. The response of the BiSrCaCu2O/sub x/ ceramic to an external magnetic field differs markedly from that of YBa2Cu3O and, in particular, -dT/sub c//dH is much greater in the bismuth sample

  6. Photoluminescence, enhanced ferroelectric, and dielectric properties of Pr{sup 3+}-doped SrBi{sub 2}Nb{sub 2}O{sub 9} multifunctional ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Zou, Hua, E-mail: zouhua_1210@163.com [Functional Materials Research Laboratory, Tongji University, Siping Road 1239, Shanghai 200092 (China); School of Mathematics and Physics, Jiangsu University of Technology, Changzhou 213001 (China); Yu, Yao; Li, Jun; Cao, Qiufeng [Functional Materials Research Laboratory, Tongji University, Siping Road 1239, Shanghai 200092 (China); Wang, Xusheng, E-mail: xs-wang@tongji.edu.cn [Functional Materials Research Laboratory, Tongji University, Siping Road 1239, Shanghai 200092 (China); Key Laboratory of Advanced Civil Engineering Materials of the Ministry of Education, Tongii University, Shanghai 200092 (China); Hou, Junwei [PetroChina Xinjiang Oilfield Company, Research Institute of Experiment and Detection, Karamay, Xinjiang834000 (China)

    2015-09-15

    Pr{sup 3+}-doped SrBi{sub 2}Nb{sub 2}O{sub 9} (SBN) multifunctional ceramics were synthesized by the conventional solid state method. The photoluminescence (PL) excitation and emission spectra, enhanced ferroelectric and dielectric properties were investigated. The X-ray diffraction (XRD) and FESEM analyses indicated that the samples were simple phase and uniform flake-structure. Under the 250–350 nm ultraviolet (UV) excitations, the red emission was obtained and the optimal emission intensity was investigated when Pr doping level was 0.005 mol. With the increasing of the Pr{sup 3+} ion contents, the ferroelectric properties were enhanced obviously. As a new multifunctional material, the Pr{sup 3+}-doped SBN ceramics could be used for a wide range of application, such as integrated electro-optical devices.

  7. 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.

  8. Synthesis of K0.5Bi0.5TiO3 nanowires and ceramics by a simple hydrothermal method

    International Nuclear Information System (INIS)

    K0.5Bi0.5TiO3 (KBT) nanowires have been successfully synthesized by a simple hydrothermal method in KOH solution, which acts as a mineralizer in the hydrothermal process. The KBT nanowires were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM). The results show that KBT nanowires with tetragonal phase have width of 5 nm and length of 200 nm. The as-prepared nanowires were employed to fabricate KBT ceramic by sintering at 1060 deg. C. The specimen exhibits εr of 710 and tan δ of 0.043 under room temperature at 1 kHz. It was found that the KBT ceramics present typical characteristics of relaxor ferroelectrics.

  9. Synthesis of K{sub 0.5}Bi{sub 0.5}TiO{sub 3} nanowires and ceramics by a simple hydrothermal method

    Energy Technology Data Exchange (ETDEWEB)

    Jiang Xiangping, E-mail: Jiangxp64@163.com [Department of Material Science and Engineering, Jing de zhen Ceramic Institute, Jing de zhen, 333001 Jiangxi (China) and Department of Applied Physics and Materials Research Center, Hong Kong Polytechnic University (Hong Kong); Lin Mei; Tu Na; Chen Chao; Li Yueming [Department of Material Science and Engineering, Jing de zhen Ceramic Institute, Jing de zhen, 333001 Jiangxi (China)

    2010-11-15

    K{sub 0.5}Bi{sub 0.5}TiO{sub 3} (KBT) nanowires have been successfully synthesized by a simple hydrothermal method in KOH solution, which acts as a mineralizer in the hydrothermal process. The KBT nanowires were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM). The results show that KBT nanowires with tetragonal phase have width of 5 nm and length of 200 nm. The as-prepared nanowires were employed to fabricate KBT ceramic by sintering at 1060 deg. C. The specimen exhibits {epsilon}{sub r} of 710 and tan {delta} of 0.043 under room temperature at 1 kHz. It was found that the KBT ceramics present typical characteristics of relaxor ferroelectrics.

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

    Directory of Open Access Journals (Sweden)

    Suchanicz J.

    2015-06-01

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

  11. 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.

  12. 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.

  13. Crystal structure and electromechanical coupling properties of Na0.5Bi2.5Ta2O9 dense ceramics

    International Nuclear Information System (INIS)

    The crystal structure of sodium bismuth tantalate, Na0.5Bi2.5Ta2O9, was analyzed by the powder X-ray-diffraction Rietveld method. The distribution of Na atoms was found to be ordered in the A site of the pseudo-perovskite (ATa2O7)2- blocks. The piezoelectric properties were effectively examined using dense bulk ceramics containing manganese oxide as the dopant. The electromechanical coupling coefficients (kij) and the electrical quality factors (Qm) are kp=10%, k31=8.3%, kt=19.7%, and Qm=3000. (orig.)

  14. 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.

  15. 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.

  16. Metal-clad superconducting tapes with high critical current density in the Y-Ba-Cu-O and Bi(Pb)-Sr-Ca-Cu-O systems

    International Nuclear Information System (INIS)

    Superconducting powders representing the Y-Ba-Cy-O (YBCO) and Bi(Pb)-Sr-Ca-Cu-O (BPSCCO) systems were used either alone or combining them with different amounts of silver powder to fabricate metal-clad superconducting tapes by the powder-in-tube method. The metallic tubes used were nickel for the YBCO system and silver for the BPSCCO system. The initial tapes were produced by cold-rolling the tubes to various thicknesses and then processed following rigorous regimens of sintering, annealing and oxygenation schedules. The YBCO tapes were generally processed by a gradientless melt-texturizing process in an oxygen atmosphere, and the BPSCCO tapes were processed by a combination of rolling and sintering operations in air and in low oxygen partial pressure. This paper reports on the effects of various compositional and processing variables on the superconductive properties of the tapes measured by the DC magnetization, AC susceptibility and direct transport current measurements. Transport critical currents greater than 600 A at 4.2K were routinely carried by the YBCO tapes. Also, for the YBCO system, the effects of silver addition to control oxygenation and nickel poisoning of the superconducting phase were studied in detail with the help of magnetization measurements. Addition of silver up to 5 wt% was found to be beneficial for critical current density in YBCO tapes. However, direct contact of the superconductor with oxygen was essential for optimum current density. On the other hand, homogenization of the precursor powder by repeated calcination and the tapes of the lowest thickness offered the most improved critical current density values of the BPSCCO system

  17. The influence of synthesis environment on magnetic properties and phase content in BSCCO superconducting ceramic obtained by spray-frozen, freeze drying technique

    International Nuclear Information System (INIS)

    In this work we discuss correlation between structural and superconducting properties determined by AC susceptibility and DC magnetization for pellets with starting composition (Bi1.7Pb0.3Sr2.0Ca2.5Cu3.5O10+x) sintered in different environments - ''on'' and ''in powder''of the same starting composition already indicated and previously calcinated in air for 100 h. Formation of the superconducting 2223-phase ((Bi,Pb)2.0Sr2.0Ca2.0Cu3.0 O10+x) is sluggish in the ''on powder'' pellets. The beginning of 2223-phase growth was observed by AC susceptibility and magnetization measurements and X-ray diffraction for 135-185 h of sintering time. Phase formation and decomposition reactions were studied. The (Sr,Ca)CuO2 decomposes in the first 20 h of sintering ''on powder'' and does not directly participate in the 2223-phase growth processes. (orig.)

  18. 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

  19. 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)

  20. 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

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

    OpenAIRE

    Mourachkine, A.

    1998-01-01

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

  2. Vortex phase diagram of Bi2Sr2CaCu2O8+δ: c-axis superconducting correlation in the different vortex phases

    Science.gov (United States)

    Goffman, M. F.; Herbsommer, J. A.; de La Cruz, F.; Li, T. W.; Kes, P. H.

    1998-02-01

    The vortex phase diagram in Bi2Sr2CaCu2O8+δ is investigated by studying the linear ac transverse permeability μ⊥=μ'⊥+μ''⊥ (hac⊥H||c axis) in a wide range of temperature and magnetic fields. At low fields (H<300 Oe)superconducting phase coherence in the c direction shows that the ordered vortex solid state is characterized by a c-axis vortex correlation length lc limited by the sample thickness d. At low temperatures (T<20 K) point disorder is sufficiently strong and the phase coherent ordered vortex solid becomes metastable. In the temperature range 20

  3. 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

  4. 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.

  5. Effects of Sr2+ doping on the electrical properties of (Bi0.5Na0.50.94Ba0.06TiO3 ceramics

    Directory of Open Access Journals (Sweden)

    Amrita Singh

    2015-03-01

    Full Text Available The influence of SrTiO3 addition on the microstructure and various electrical properties of (Bi0.5Na0.50.94Ba0.06TiO3 (BNTBT6 ceramics, fabricated by a conventional high temperature solid state reaction, was investigated. Analysis of X-ray diffraction patterns revealed the formation of phase pure materials with tetragonal unit cell structure, tetragonality parameter c/a in the interval from 0.9940 to 1.0063 and crystallite sizes ranging from 33–76 nm for addition of 0.2 to 1 wt.% of SrTiO3. SEM studies indicated that Sr2+ doping led to decrease in grain size and non-homogeneity of grain distribution for higher SrTiO3 amount (>0.6 wt.%. Complex impedance, modulus, and conductivity studies indicated the presence of grains and grain boundary contribution, non-Debye type of relaxation and NTCR behaviour of the test ceramic samples. Temperature dependent real part of complex permittivity showed peaks at 475 °C and the dielectric loss tangent showed peaks corresponding to 125 °C and 475 °C for almost all compositions. AC activation energies, computed using Arrhenius relation in the temperature range of 325–500 °C for the BNTBT6 ceramic compositions having SrTiO3 concentration from 0.2 to 1.0 wt.%, were seen to have maximal values at the lowest measurement frequency. Amongst the different chosen doped BNTBT6 ceramic compositions, the composition having 0.6 wt.% of SrTiO3 showed the best ferroelectric and piezoelectric response with maximum value of Pr (8.24 µC/cm2, minimum value of Ec (5.73 kV/mm and maximum d33 value (∼46 pC/N.

  6. 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.

  7. R dependence of superconductivity and thermopower in the Bi2Sr2-xRxCuOy (R=La, Sm and Eu) system

    International Nuclear Information System (INIS)

    We have grown single crystals of Bi2Sr2-xRxCuOy with R=La, Sm and Eu for a wide range of R content x and measured resistivity and the thermopower. The relation between the value of thermopower at 290K, S(290), and the superconducting transition temperature Tc determined simultaneously on the same single crystal clearly shows that Tc at the optimal doping Tcmax strongly depends on the R element. More importantly, we found that the range of S(290) values of samples with a non-zero Tc is narrower when the R element is changed to one with a smaller ionic radius. The narrowing of the range of S(290) values indicates that the range of carrier density where high-Tc superconductivity occurs in this system depends on the R element. We argue that these behaviors are a consequence of the difference in the transfer integrals in the CuO2 plane accompanied with the structural change caused by replacing the R element to one with a different ionic radius

  8. 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.

  9. 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.

  10. Monofilamentary Ag/Bi:2212 tapes - effects of silver powder addition

    International Nuclear Information System (INIS)

    The Bi-Sr-Ca-Cu-O system has been one of the most studied superconducting ceramic materials for industry applications. The most of the studies with this aim are on silver/ceramic composites, due to the benefits and great compatibility of this metal with the oxide. Tapes made by the powder in tube (PIT) method have been successfully tested in pilot power plants in many countries but in Brazil. In this paper, 5, 10, and 20-wt% silver powders are introduced to compose the core of the tape along with the Bi:2212 ceramic powder. The results of electrical experiments are compared with those made with no silver addition Ag tapes. The best current density, at 60 K and no applied magnetic field, was found for the 10-wt% silver proportion, doubling the value obtained for the tape with no silver in the core. (orig.)

  11. 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)

  12. Coexistence of two sharp-mode couplings and their unusual momentum dependence in the superconducting state of Bi2Sr2CaCu2O(8+δ) revealed by laser-based angle-resolved photoemission.

    Science.gov (United States)

    He, Junfeng; Zhang, Wentao; Bok, Jin Mo; Mou, Daixiang; Zhao, Lin; Peng, Yingying; He, Shaolong; Liu, Guodong; Dong, Xiaoli; Zhang, Jun; Wen, J S; Xu, Z J; Gu, G D; Wang, Xiaoyang; Peng, Qinjun; Wang, Zhimin; Zhang, Shenjin; Yang, Feng; Chen, Chuangtian; Xu, Zuyan; Choi, H-Y; Varma, C M; Zhou, X J

    2013-09-01

    High-resolution laser-based angle-resolved photoemission measurements have been carried out on Bi2Sr2CaCu2O(8+δ) (Bi2212) superconductors to investigate momentum dependence of electron coupling with collective excitations (modes). Two coexisting energy scales are clearly revealed over a large momentum space for the first time in the superconducting state of the overdoped Bi2212 superconductor. These two energy scales exhibit distinct momentum dependence: one keeps its energy near 78 meV over a large momentum space while the other changes its energy from ∼40  meV near the antinodal region to ∼70  meV near the nodal region. These observations provide a new picture on momentum evolution of electron-boson coupling in Bi2212 that electrons are coupled with two sharp modes simultaneously over a large momentum space in the superconducting states. Their unusual momentum dependence poses a challenge to our current understanding of electron-mode-coupling and its role for high-temperature superconductivity in cuprate superconductors. PMID:25166699

  13. 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).

  14. 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)

  15. 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.

  16. Synthesis, electrical and thermal properties of Bi4V2-xYxO11 (x=0.0 and 0.10) ceramics

    Science.gov (United States)

    Sahu, S.; Roy, M.

    2014-04-01

    Polycrystalline ceramic samples of Bi4V2-xYxO11 (x=0.0 and 0.10) have been synthesized by standard solid state reaction method. The formation of the compounds has been verified by room temperature (RT) X-ray diffraction. 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 specific heat and heat flow of both the compounds were determined as a function of temperature using Modulated Differential Scanning Calorimetry (MDSC).

  17. Synthesis, electrical and thermal properties of Bi4V2-xNbxO11 (x=0.0 and 0.06) ceramics

    Science.gov (United States)

    Sahu, S.; Roy, M.

    2013-06-01

    Polycrystalline ceramic samples of Bi4V2-xNbxO11 (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).

  18. Synthesis, electrical and thermal properties of Bi4V2-xZrxO11 (x=0.0 & 0.02) ceramics

    Science.gov (United States)

    Sahu, S.; Barbar, S. K.; Jangid, S.; Roy, M.

    2013-02-01

    Polycrystalline ceramic samples of Bi4V2-xZrxO11 (x=0.0 & 0.02) have been synthesized by standard solid state reaction method. The formation of the compounds has been verified by room temperature (RT) X-ray diffraction. 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 = σ°exp)-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).

  19. Synthesis, electrical and thermal properties of Bi4V2−xYxO11 (x=0.0 and 0.10) ceramics

    International Nuclear Information System (INIS)

    Polycrystalline ceramic samples of Bi4V2−xYxO11 (x=0.0 and 0.10) have been synthesized by standard solid state reaction method. The formation of the compounds has been verified by room temperature (RT) X-ray diffraction. 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 specific heat and heat flow of both the compounds were determined as a function of temperature using Modulated Differential Scanning Calorimetry (MDSC)

  20. 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.

  1. 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.

  2. Spark plasma sintering consolidation of Bi1.65Pb0.35Sr2Ca2Cu3010+δ ceramic samples

    International Nuclear Information System (INIS)

    Pre-reacted powders of (Bi-Pb)2Sr2Ca2Cu3O10+δ (Bi-2223) were consolidated by using the spark plasma sintering (SPS) technique under vacuum and at different consolidated temperatures TD. We have found that the transport properties of SPS samples depend on their oxygen content because the SPS process is performed under vacuum. From these results we have inferred that SPS samples are oxygen deficient and that a post-annealing treatment, performed in air for a brief time interval, is needed to restore such a deficiency. Measurements of temperature dependence of the thermal conductivity, κ(T), were performed in all SPS samples including a reference sample sintered at 845 °C in air. The results indicate that the electronic contribution to the thermal conductivity in all samples is very low. Values of κ were found to be higher in SPS samples mostly because of their high volume density of ∼ 5.7 g/cm3. We have also performed measurements of the critical current density as a function of the applied magnetic field, Jc(Ba). All samples display a clear Josephson-like behavior and low values of the superconducting critical current density at zero applied magnetic field. The experimental results indicate that the oxygen deficiency in SPS samples is marked near the grain boundaries. This suggests the occurrence of grains with core-shell morphology, where the width of the shell is consolidation temperature dependent.

  3. 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.

  4. Phase transformations in multiferroic Bi1−xLaxFe1−yTiyO3 ceramics probed by temperature dependent Raman scattering

    International Nuclear Information System (INIS)

    Optical phonons and phase transitions of Bi1−xLaxFe1−yTiyO3 (BLFTO, 0.02 ≤ x ≤ 0.12, 0.01 ≤ y ≤ 0.08) ceramics have been investigated by Raman scattering in the temperature range from 80 to 680 K. Four phase transitions around 140, 205, 570, and 640 K can be observed. The Raman modes are sensitive to the spin reorientation around 140 and 205 K, owing to the strong magnon-phonon coupling. The transformation around 570 K is a structural transition from rhombohedral to orthorhombic phase due to an external pressure induced by the chemical substitution. The anomalies of the phonon frequencies near Néel temperature TN have been discussed in the light of the multiferroicity. Moreover, it was found that the structural transition temperature and TN of BLFTO ceramics decrease towards room temperature with increasing doping composition as a result of size mismatch between substitution and host cations.

  5. 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...

  6. 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.

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

    KAUST Repository

    Hang, Qiming

    2013-09-07

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

  8. 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.

  9. Critical current density, irreversibility line, and flux creep activation energy in silver-sheathed Bi[sub 2]Sr[sub 2]Ca[sub 2]Cu[sub 3]O[sub x] superconducting tapes

    Energy Technology Data Exchange (ETDEWEB)

    Shi, D.; Wang, Z.; Sengupta, S.; Smith, M. (Argonne National Lab., IL (United States)); Goodrich, L.F. (National Inst. of Standards and Technology (NEL), Boulder, CO (United States). Electromagnetic Technology Div.); Dou, S.X.; Liu, H.K.; Guo, Y.C. (New South Wales Univ., Kensington, NSW (Australia). School of Materials and Engineering)

    1992-08-01

    Transport data, magnetic hysteresis and flux creep activation energy experimental results are presented for silver-sheathed high-[Tc] Bi[sub 2]Sr[sub 2]Ca[sub 2]Cu[sub 3]O[sub x] superconducting tapes. The 110 K superconducting phase was formed by lead doping in a Bi-Sr-Ca-Cu-0 system. The transport critical current density was measured at 4.0 K to be 0.7 [times] 10[sup 5] A/cm[sup 2] (the corresponding critical current is 74 A) at zero field and 1.6 [times] 10[sup 4] A/cm[sup 2] at 12 T for H[parallel]ab. Excellent grain alignment in the a-b plane was achieved by a short-melting method, which considerably improved the critical current density and irreversibility line. Flux creep activation energy as a function of current is obtained based on the magnetic relaxation measurements.

  10. Critical current density, irreversibility line, and flux creep activation energy in silver-sheathed Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} superconducting tapes

    Energy Technology Data Exchange (ETDEWEB)

    Shi, D.; Wang, Z.; Sengupta, S.; Smith, M. [Argonne National Lab., IL (United States); Goodrich, L.F. [National Inst. of Standards and Technology (NEL), Boulder, CO (United States). Electromagnetic Technology Div.; Dou, S.X.; Liu, H.K.; Guo, Y.C. [New South Wales Univ., Kensington, NSW (Australia). School of Materials and Engineering

    1992-08-01

    Transport data, magnetic hysteresis and flux creep activation energy experimental results are presented for silver-sheathed high-{Tc} Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} superconducting tapes. The 110 K superconducting phase was formed by lead doping in a Bi-Sr-Ca-Cu-0 system. The transport critical current density was measured at 4.0 K to be 0.7 {times} 10{sup 5} A/cm{sup 2} (the corresponding critical current is 74 A) at zero field and 1.6 {times} 10{sup 4} A/cm{sup 2} at 12 T for H{parallel}ab. Excellent grain alignment in the a-b plane was achieved by a short-melting method, which considerably improved the critical current density and irreversibility line. Flux creep activation energy as a function of current is obtained based on the magnetic relaxation measurements.

  11. 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.)

  12. Structural, electrical and magnetic properties of Bi{sub 0.90}La{sub 0.10}Fe{sub 0.90}Co{sub 0.10}O{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Muneeswaran, M.; Giridharan, N. V., E-mail: giri@nitt.edu [Advanced Functional Materials Laboratory, Department of Physics, National Institute of Technology, Tiruchirappalli-620015, Tamil Nadu (India); Bhuvaneswari, S.; Senguttuvan, G. [Department of Physics, Anna University Chennai, BIT Campus, Tiruchirappalli-620024 (India)

    2014-04-24

    Multiferroic Bi{sub 0.90}La{sub 0.10}Fe{sub 0.90}Co{sub 0.10}O{sub 3} ceramics have been synthesized via soft chemical co-precipitation method. From the X-ray diffraction analysis, ceramic powder sintered at 600°C was found to be single phase belonging to the rhombohedral structure with R3c space group confirmed by Rietveld analysis. Further, dielectric, Leakage and magnetic studies were performed at room temperature.

  13. Brief review of recent superconductivity research at NIST (National Institute of Standards and Technology). Bi-monthly report

    Energy Technology Data Exchange (ETDEWEB)

    Lundy, D.R.; Swartzendruber, L.J.; Bennett, L.H.

    1989-01-01

    A brief overview of recent superconductivity research at NIST is presented. Emphasis is placed on the new high-temperature oxide superconductors, though mention is made of important work on low-temperature superconductors, and a few historical notes are included. For the new high-temperature superconductors, research activities include determination of physical properties such as elastic constants and electronics structure, development of new techniques such as magnetic-field modulated microwave absorption and determination of phase diagrams and crystal structure. For the low-temperature superconductors, research spans studying the effect of stress on current density to the fabrication of a new Josephson junction voltage standard.

  14. 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.

  15. AC losses of mono- and multifilamentary high-Tc superconducting (Bi,Pb)2Sr2Ca2Cu3O10/Ag tapes

    International Nuclear Information System (INIS)

    In this thesis the ac losses of high-temperature superconductors (HTSC) were measured and analyzed by means of model calculations. The investigated silver sheathed Mono- and Multifilamentary tapes are based on the HTSC material (Bi,Pb)2Sr2Ca2Cu3O10 (Bi-2223/Ag). The losses were investigated in externally applied magnetic field changes as well as in the self-field of a transport current at temperatures of 4.2 K and 77 K. A detailed knowledge of the ac loss dependence on frequency and amplitude of these tapes is important for future transformer or magnet applications. While measuring the amplitude dependence we found - depending on the sample - a strong influence of the degree of the grain alignment (granularity) in the superconducting material upon the magnetization and hysteresis losses Qh. We could explain these effects which are not known in the technical relevant low-temperature superconductors by a superposition of the magnetic moments of the grain- and sample currents (intra- and intergranular screening currents). In the frame of this model we were able to divide the total measured losses into their inter-and intragranular contributions and we could quantitatively describe the losses of the grain and the sample system separately. The frequency dependence of the losses, depending on the extremely nonlinear voltage-current (E-j) characteristics of the high-temperature materials could be explained with a newly developed extension of the Critical State model. From the directly measured E-j relations we also calculated the internal current- and field distributions in the samples with the field change velocity B as a parameter. (author) figs., tabs., refs

  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. 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

  18. 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)

  19. Enhanced thermoelectric properties of the hole-doped Bi2-xKxSr2Co2Oy ceramics

    Science.gov (United States)

    Gao, Feng; He, Qinglin; Cao, Ruijuan; Wu, Fang; Hu, Xing; Song, Hongzhang

    2015-09-01

    In this paper, the influence of K element doping on the thermoelectric properties of the Bi2-xKxSr2Co2Oy (x = 0.00, 0.05, 0.10, 0.15, and 0.20) samples prepared by the solid-state reaction method were investigated from 333 K to 973 K. It was shown that due to the p-type K doping the electrical resistivity of the doped sample can be reduced remarkably as compared with the undoped sample, especially for the optimum doped sample Bi1.9K0.1Sr2Co2Oy. The Seebeck coefficients of the K doped samples have only a slight decrease as compared with the undoped sample. As a result of the remarkable reduction of the electrical resistivity the power factor of the doped sample have a significant improvement. The thermal conductivity of the samples is depressed due to the defects caused by K doping. As an overall result, the dimensionless figure of merit (ZT) of the Bi1.9K0.1Sr2Co2Oy sample reaches a maximum value of 0.3 at 973 K, being 93% higher than that of the undoped sample.

  20. 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

  1. (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)

  2. 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.

  3. 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

  4. 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.

  5. 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

  6. 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.

  7. Electromechanical and electrical properties of Bi0.5Na0.5Ti1−xMnxO3−δ ceramics with high remnant polarization

    International Nuclear Information System (INIS)

    Highlights: • High remnant polarization of 48.5 μC/cm2 for BNTM25 ceramics was obtained. • No apparent fatigue was observed after switching over 106 cycles for BNTM25 ceramics. • Electromechanical quality factor (Qm) of BNTM50 ceramics reaches to 901. - Abstract: The perovskite oxides Bi0.5Na0.5Ti1−xMnxO3−δ (BNTM10000x, x = 0%, 0.25%, 0.5%, 0.75%, 1%, 1.5%, 2%) were prepared via the conventional solid state reaction method. The crystal structure of BNT and BNTM25 ceramics were refined by the Rietveld method with powder X-ray diffraction at room temperature. A production of small amount of oxygen vacancies, a significant enhancement in tetragonality and a grain size effect due to the MnO2 doping, led to the enhancements of the electromechanical and electrical properties of Bi0.5Na0.5Ti1−xMnxO3−δ ceramics, and the optimized modification was x = 0.25%. The electrical properties of modified samples were deteriorated with further doping (x = 0.5–2%), owing to an obvious ferroelectric to relaxor phase transition and an increase in the concentration of oxygen vacancies. The BNTM25 ceramics was found to have a high remnant polarization (Pr) of 48.5 μC/cm2, an electromechanical coupling factor (kp) of 0.18, an electro-field-induced strain (Stotal) of 0.24% and a piezoelectric coefficient (d33) of 105 pC/N. In addition, almost no profound fatigue was observed after switching over 106 cycles at room temperature, indicating a potential application as lead-free piezoelectric materials

  8. 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

  9. A high Tc superconducting liquid nitrogen level sensor

    International Nuclear Information System (INIS)

    Full text: The dramatic resistance change in the superconducting-normal transition temperature range enables a high Tc superconductor to be considered for designing a liquid nitrogen level sensor. A (Bi,Pb)2Sr2Ca2Cu3O10+x Ag clad superconducting wire is selected and tested as a continuous liquid nitrogen level sensor to investigate the possibility for this application. The (Bi,Pb)2Sr2Ca2Cu3O10+x Ag clad superconducting wire has approximately 110 K critical temperature, with more flexible and stable properties compared with bulk shape ceramic high Tc superconductors. The voltage drops across the sensor are tested with different immersion lengths in liquid nitrogen. The accuracy of the HTS sensor is analysed with its dR/dT in the superconducting-normal transition range. The voltage signal is sensitive to liquid nitrogen level change, and this signal can be optimized by controlling the transport current. The problems of the Ag clad superconductor are that the Ag sheath thermal conductivity is very high, and the sensor normal resistance is low. These are the main disadvantages for using such a wire as a continuous level sensor. However, a satisfactory accuracy can be achieved by control of the transport current. A different configuration of the wire sensor is also designed to avoid this thermal influence

  10. Fabrication process and superconducting behavior of sintered Y1 Ba2 Cu3 O7 ceramic samples

    International Nuclear Information System (INIS)

    Eletric and superconducting properties of Y1 Ba2 Cu3 O7 sintered samples have been measured at different temperatures and in the presence of a magnetic field. The effects of some fabrication parameters, e.g. sintering temperature and time, on these properties have been investigated. The limiting affect on the critical current density through the Y1 Ba2 Cu3 O7 samples is discussed in terms of the inter-grain coupling. Highest density samples sintered at temperature above 950 Co sustain lower critical current densities, and are more sensitive to the magnetic field

  11. 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

  12. Measuring the dielectric permittivity and loss angle tangent of the ceramic windows for power input in a superconducting resonator

    International Nuclear Information System (INIS)

    The results of calculations and experimental studies, aimed at creating the facility for determining the dielectric constant and the loss angle tangent of the cylindrical form ceramic samples, are presented. The version with cylindrical resonator on the E010-type oscillations with the beyond-the-limit waveguide, attached to one of the resonator faces, was selected on the basis of the analysis of measuring the accuracy and convenience of applying the facility under the conditions of serial measurements of samples with various geometrical dimensions on the fixed frequency

  13. Magnetic properties and irreversibility behavior in Ag-sheathed Bi-based superconducting wires fabricated using a controlled melt procedure

    Energy Technology Data Exchange (ETDEWEB)

    Dou, S.X.; Liu, H.K.; Guo, Y.C. [New South Wales Univ., Kensington, NSW (Australia). School of Materials Science and Engineering; Shi, D.L. [Argonne National Lab., IL (United States); Sumption, M.D.; Collings, E.W. [Battelle Memorial Inst., Columbus, OH (United States)

    1992-12-01

    A significant enhancement of the in-field J{sub c} of Ag-clad (Bi,Pb)-Sr-Ca-Cu-0 (BPSCCO:2223) wires has been achieved using a controlled melt procedure. The greatly reduced weak linking has resulted in an extended plateau regime in the J{sub c}-H curve. J{sub c}s of 40,000 A/cm{sup 2} at 77 K (self field) and 9,000 A/cm{sup 2} at 77 K (1 T) have been achieved. The improved J. H characteristics may be attributed to microstructures consisting of uniform grain alignment throughout the entire cross section, intimate connection between grains, impurities within the grains, and an optimal level of dispersed 2212 phase. Irreversibility line measurements using both AC susceptibility in DC fields (reported elsewhere), and magnetization measurements, have indicated that flux pinning can be enhanced in the melt-processed samples over the results of normal solid-state processing with its less-than optimal 2212-phase content. But sufficiently long annealing times during the ``normal`` route may achieve 2212-phase content and J{sub c}s which are comparable to those of melt-processed samples.

  14. Magnetic properties and irreversibility behavior in Ag-sheathed Bi-based superconducting wires fabricated using a controlled melt procedure

    Energy Technology Data Exchange (ETDEWEB)

    Dou, S.X.; Liu, H.K.; Guo, Y.C. (New South Wales Univ., Kensington, NSW (Australia). School of Materials Science and Engineering); Shi, D.L. (Argonne National Lab., IL (United States)); Sumption, M.D.; Collings, E.W. (Battelle Memorial Inst., Columbus, OH (United States))

    1992-12-01

    A significant enhancement of the in-field J[sub c] of Ag-clad (Bi,Pb)-Sr-Ca-Cu-0 (BPSCCO:2223) wires has been achieved using a controlled melt procedure. The greatly reduced weak linking has resulted in an extended plateau regime in the J[sub c]-H curve. J[sub c]s of 40,000 A/cm[sup 2] at 77 K (self field) and 9,000 A/cm[sup 2] at 77 K (1 T) have been achieved. The improved J. H characteristics may be attributed to microstructures consisting of uniform grain alignment throughout the entire cross section, intimate connection between grains, impurities within the grains, and an optimal level of dispersed 2212 phase. Irreversibility line measurements using both AC susceptibility in DC fields (reported elsewhere), and magnetization measurements, have indicated that flux pinning can be enhanced in the melt-processed samples over the results of normal solid-state processing with its less-than optimal 2212-phase content. But sufficiently long annealing times during the normal'' route may achieve 2212-phase content and J[sub c]s which are comparable to those of melt-processed samples.

  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. 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

  17. The peculiarities of behavior of magnetic flux and its noise in HTSC ceramics

    International Nuclear Information System (INIS)

    The spectral density of magnetic flux noise inside a HTSC ceramics is studied. The time dependence of flux drift velocity is determined for different strengths of frozen magnetic field. The measurements are made on two series of Bi-ceramics samples (Bi2-x Pbx Sr2 Ca2 Cu3 Oy) prepared by different techniques and on Y-ceramics ones (Y Ba2 Cu3 O7-σ). A nonequilibrium component of noise and its dependence on frozen magnetic field are measured. It is shown that the spectral density of white noise independent of magnetic field value is responsible for by HTSC ceramics granularity and defined by grain sizes while the major field-dependent part of while noise is caused by the oscillations of vortices almost at equilibrium. The 1/f noise spectral density is related to thermal excitation of vortices in the HTSC ceramics. Besides, an excess telegraph noise is observed which is caused by the vortex slip into superconducting loops consisting of ceramics granules and Josephson junctions in between. These mechanism can be used to explain qualitatively the experimental data on white noise as well as on equilibrium and nonequilibrium 1/f ones

  18. The influence of synthesis environment and time on volumetric characteristics of BSCCO superconducting ceramic obtained by spray-frozen, freeze drying technique

    International Nuclear Information System (INIS)

    The influence of the intermediate heat treatment time and synthesis environment in which samples with nominal composition Bi:Pb:Sr:Ca:Cu=1.7:0.3:2.0:2.5:3.5 have been placed on the phase content and volumetric characteristics of the ceramic were studied. Final sintering (235 h) of the pellets was done by placing them ''in'' and ''on powder'' calcinated in air at 847 C for 100 hours with composition as above. During intermediate heat treatment (IHT) relativ volume changes (ΔV/Vo) attein 1.0% for 7 h and a minimum value of -5.0% for 3 h. The (ΔV/V0) and (Δm/m0) for ''in powder'' pellets sintered for 235 hours depend on this parameters for (IHT) pellets treated for 1, 3, 5, 7 h while for ''on powder'' pellets do not. Minimum and maximum values for ΔV/V0 determined on ''in powder'' pellets were -1.7% and 6.3% respectively. ΔV/V0 for ''on powder'' pellets was approximately constant at -9.7%. ''In powder'' pellets consist of more then 70% of 2223 phase determined by X-ray diffraction while ''on powder'' pellets of 30%. Sintering ''on powder'' does not lead to the swelling of the pellets but it is less favourable to 2223 phase formation than sintering ''in powder'' showing a very long nucleation period for 2223 phase. (orig.)

  19. 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.

  20. 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.

  1. Composite ceramic superconducting wires for electric-motor applications. Annual report No. 1, 30 June 1988-30 June 1989

    Energy Technology Data Exchange (ETDEWEB)

    Holloran, J.W.

    1989-07-07

    This report describes progress on developing Y-123 wire for an HTSC motor. The wire development involves synthesis of Y-123 powder, spinning polymer-containing green fiber, heat treating the fiber to produce metallized superconducting filaments, and characterizing the electrical properties. A melt spinning process was developed for producing 125-micron-diameter green fiber containing 50 vol% Y-123. This fiber can be braided for producing transposed multifilamentary wire. A process was developed to coat green fiber with silver alloys which can be continuous sintering. A second process for multifilamentary ribbon wire is also being developed. The Y-123 filaments have 77 deg self-field Jc values up to 2600 A/sq cm, but Jc is reduced to 10 A/sq cm at 800 G. Preliminary data are presented on mechanical properties. A DC homopolar motor with an iron magnetic circuit is being designed to operate with early HTSC wire.

  2. Piezoelectric properties of new ternary Bi1/2(Na, Li)1/2TiO3-(Bi1/2K1/2)TiO3-Ba0.85Ca0.15Ti0.90Zr0.10O3 ceramics

    International Nuclear Information System (INIS)

    0.852[Bi1/2(Na1-x Lix)1/2]TiO3-0.110(Bi1/2K1/2)TiO3-0.038Ba0.85Ca0.15Ti0.90Zr0.10O3 (BNLT-BKT-BCTZ-x) new ternary piezoelectric ceramics were fabricated by the conventional solid-state method, and their piezoelectric properties as a function of the Li content were mainly investigated. A stable solid solution with a single perovskite structure has been formed, and the depolarization temperature (Td) of these ceramics was identified by using the temperature dependence of the dielectric loss. The Td value of these ceramics gradually decreases, while the Tm value increases with increasing the Li content. The dielectric constant increases and the dielectric loss decreases with increasing the Li content, and an enhanced piezoelectric behavior of d33∝223 pC/N and kp∝35.2 % has been demonstrated in these ceramics with x=0.06. (orig.)

  3. Role of (Bi1/2K1/2)TiO3 in the dielectric relaxations of BiFeO3-(Bi1/2K1/2)TiO3 ceramics

    Science.gov (United States)

    Cheon, Chae Il; Choi, Jin Hong; Kim, Jeong Seog; Zang, Jiadong; Frömling, Till; Rödel, Jürgen; Jo, Wook

    2016-04-01

    Temperature-dependent dielectric relaxations of (1 - x)BiFeO3-x(Bi1/2K1/2)TiO3 (BF-BKT) lead-free piezoceramics (0.4 ≤ x ≤ 0.8) were investigated via impedance spectroscopic techniques. Regardless of the compositions, the dielectric maximum temperatures exhibit a frequency-dependent dispersion, originating from a Debye relaxation due to the presence of oxygen vacancies. It was also observed that there exist local dielectric maxima due to the relaxation of polar nanoregions as a shoulder on the lower temperature side. The onset temperature for the Debye-type relaxation decreased with decreasing BKT content, gradually overlapping with the low-temperature dielectric dispersion from the relaxation of polar nanoregions. It is proposed that the role of BKT in the BF-BKT system is to enhance the random fields that favor a relaxor state and to suppress the Debye-type relaxation of oxygen vacancy related dipoles.

  4. Evolution of phase transformation behavior and dielectric temperature stability of BaTiO3–Bi(Zn0.5Zr0.5)O3 ceramics system

    International Nuclear Information System (INIS)

    Highlights: ► (1 − x)BaTiO3–xBi(Zn0.5Zr0.5)O3 ceramics were synthesized. ► A systematic structural change was observed near x = 0.07 and x = 0.4. ► A change from a normal ferroelectric behavior to diffusive and dispersive relaxor-like characteristic was also observed. ► (1 − x)BT–xBZZ ceramics show good dielectric temperature stability over a wide temperature range. - Abstract: (1 − x)BaTiO3–xBi(Zn0.5Zr0.5)O3 [(1 − x)BT–xBZZ, 0.01 ⩽ x ⩽ 0.6] ceramics were synthesized by solid-state reaction technique. Based on the X-ray diffraction data analysis, a systematic structure change from the ferroelectric tetragonal phase to pseudocubic phase and the pseudocubic phase to orthorhombic phase was observed near x = 0.07 and x = 0.4 at room temperature, respectively. Dielectric measurements show a dielectric anomaly, over the temperature range from 50 to 200 °C for the compositions with 0.03 ⩽ x ⩽ 0.09. A change from a normal ferroelectric behavior to diffusive and dispersive relaxor-like characteristic was also observed. Moreover, (1 − x)BT–xBZZ ceramics show good dielectric temperature stability over a wide temperature range, which indicates that these ceramics can be applied in the temperature stability devices.

  5. 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

  6. 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

  7. 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

  8. 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.

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

    Directory of Open Access Journals (Sweden)

    Ansu K. Roy

    2013-06-01

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

  10. Dielectric properties of (Na0.5Bi0.5)TiO3-Ba0.7Sr0.3Sn0.02Ti0.98O3 composite ceramics

    Science.gov (United States)

    Wang, Jing; Rong, Guijuan; Liu, Lei; Cheng, Haiyan; Jiang, Qi; Li, Chuangchuang; Wang, Mengmeng

    2016-05-01

    Lead-free x(Na0.5Bi0.5)TiO3-(1 ‑ x)Ba0.7Sr0.3Sn0.02Ti0.98O3 (NBT-BSST) ceramics are prepared by a wet solid-phase reaction method. The effect of NBT/BSST ratio on phase structure, microstructure and dielectric properties has been investigated in detail. The X-ray diffraction (XRD) analysis illustrates that the composites are composed of tetragonal perovskite. With increasing NBT content, the ceramic capacitors display stronger temperature stability in its dielectric behavior. A great enhance of dielectric properties and other electric parameters is obtained in this system by properly modulating the compositions. For example, the composite ceramics with 30% NBT content possess a large dielectric constant (𝜀r) of 3200 and a low dielectric loss (tan δ) of 0.09. The temperature coefficient of capacitance of NBT-BSST varies from ‑50% to 20% while the NBT content is 30% at the whole range of measured temperature. The results show that NBT-BSST ceramics are a good candidate of lead-free dielectric materials.

  11. 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)

  12. Direct Spectroscopic Evidence for Phase Competition between the Pseudogap and Superconductivity in Bi2Sr2CaCu2O8+δ

    Energy Technology Data Exchange (ETDEWEB)

    Hashimoto, Makoto [SLAC National Accelerator Lab., Menlo Park, CA (United States); Nowadnick, Elizabeth A. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., CA (United States); He, Rui-Hua [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Vishik, Inna M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., CA (United States); Moritz, Brian [SLAC National Accelerator Lab., Menlo Park, CA (United States); Univ. of North Dakota, Grand Forks, ND (United States); He, Yu [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., CA (United States); Tanaka, Kiyohisa [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., CA (United States); Osaka Univ. (Japan); Moore, Robert G. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Lu, Donghui [SLAC National Accelerator Lab., Menlo Park, CA (United States); Yoshida, Yoshiyuki [National Institute of Advanced Industrial Science and Technology, Tsukuba (Japan); Ishikado, Motoyuki [National Institute of Advanced Industrial Science and Technology, Tsukuba (Japan); Japan Atomic Energy Agency, Tokai (Japan); Sasagawa, Takao [Tokyo Inst. of Technology (Japan); Fujita, Kazuhiro [Univ. of Tokyo (Japan); Cornell Univ., Ithaca, NY (United States); Ishida, Shigeyuku [Univ. of Tokyo (Japan); Uchida, Shinichi [Univ. of Tokyo (Japan); Eisaki, Hiroshi [National Institute of Advanced Industrial Science and Technology, Tsukuba (Japan); Hussain, Zahid [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Devereaux, Thomas P. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Shen, Zhi-Xun [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., CA (United States)

    2014-11-02

    In the high-temperature (Tc) cuprate superconductors, increasing evidence suggests that the pseudogap, existing below the pseudogap temperature T*, has a distinct broken electronic symmetry from that of superconductivity. Particularly, recent scattering experiments on the underdoped cuprates have suggested that a charge ordering competes with superconductivity. However, no direct link of this physics and the important low-energy excitations has been identified. We report an antagonistic singularity at Tc in the spectral weight of Bi2Sr2CaCu2O8+δ as a compelling evidence for phase competition, which persists up to a high hole concentration p ~ 0.22. Comparison with a theoretical calculation confirms that the singularity is a signature of competition between the order parameters for the pseudogap and superconductivity. Our observation of the spectroscopic singularity at finite temperatures over a wide doping range provides new insights into the nature of the competitive interplay between the two intertwined phases and the complex phase diagram near the pseudogap critical point.

  13. Effect of substitution of Ce on superconducting properties of Bi1.7Pb0.3Sr2Ca2-xCexCu3O10+δ system

    International Nuclear Information System (INIS)

    We have investigated the superconducting properties of the Bi1.7 Pb0.3Sr2Ca2-xCexCu3O10+δ system with x = 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 c-parameter with increased substitution of Ce at Ca site and volume fraction of high Tc (2: 2: 2: 3) phase decreases and low Tc 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 x = 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 Tc of the system. (author)

  14. Microstructure, electrical properties of Bi{sub 2}NiMnO{sub 6}-doped 0.935(Bi{sub 1/2}Na{sub 1/2}) TiO{sub 3}–0.065BaTiO{sub 3} lead-free piezoelectric ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Renfei [College of Materials Science and Engineering, Liaocheng University, Liaocheng 252059 (China); Xu, Zhijun, E-mail: zhjxu@lcu.edu.cn [College of Materials Science and Engineering, Liaocheng University, Liaocheng 252059 (China); Chu, Ruiqing; Hao, Jigong; Du, Juan [College of Materials Science and Engineering, Liaocheng University, Liaocheng 252059 (China); Li, Guorong [Shanghai Institute of Ceramics, Chinese Academy of Science, Shanghai 200050 (China)

    2015-05-25

    Highlights: • The BNT–BT–xBNMO with appropriated BNMO exhibited optimum electrical properties. • It has a relatively high remnant polarization P{sub r} of 31 μC/cm{sup 2}. • It exhibits high planar electromechanical coefficient k{sub p} of 31%. • It shows large piezoelectric constant d{sub 33} of 229 pC/N. • The modified BNT–BT ceramics are promising lead-free piezoelectric candidates. - Abstract: The 0.935Bi{sub 1/2}Na{sub 1/2}TiO{sub 3}–0.065BaTiO{sub 3}–xmol⋅Bi{sub 2}NiMnO{sub 6}(x = 0–0.008) (abbreviated as BNT–BT6.5–xBNMO) lead-free piezoelectric ceramics were fabricated by conventional solid-state reaction method and the effects of BNMO addition on microstructure and electrical properties of the ceramics were investigated. Results show that all samples have formed dense structures with a large relative density > 95%. X-ray diffraction (XRD) patterns show all compositions had a pure perovskite structure, suggesting BNMO effectively diffused into the BNT–BT6.5 lattice to form a solid solution. SEM images indicate that BNMO modified ceramics have a clear grain boundary and a uniformly distributed grain size. The measurements of electrical properties reveal that the electrical properties of BNT–BT–xBNMO ceramics have been greatly improved by certain amount of BNMO substitutions. At room temperature, the BNT–BT–xBNMO ceramics with appropriated BNMO exhibited optimum ferroelectric and piezoelectric properties with a relatively high remnant polarization P{sub r} of 31 μC/cm{sup 2}, high planar electromechanical coefficient k{sub p} of 31% and large piezoelectric constant d{sub 33} of 229 pC/N, respectively. These results indicate that the modified BNT–BT6.5 ceramics are promising lead-free piezoelectric candidates for practical applications.

  15. Electric-field-temperature phase diagram of Mn-doped Bi0.5(Na0.9K0.1)0.5TiO3 ceramics

    International Nuclear Information System (INIS)

    An electric field–temperature (E-T) phase diagram for a lead-free 0.5 mol. % Mn-doped Bi(Na0.1K0.9)TiO3 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 Bi0.5(Na0.1K0.9)0.5TiO3 ceramics were proposed as a potential piezoceramic material

  16. 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.

  17. 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.

  18. 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

  19. 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 ...

  20. 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.

  1. The effect of K-na co-doping on the formation and particle size of Bi-2212 phase

    Science.gov (United States)

    Kır, M. Ebru; Özkurt, Berdan; Aytekin, M. Ersin

    2016-06-01

    Superconducting K-Na co-doped Bi2Sr2KxCa1Cu1.75Na0.25Oy (x=0, 0.05, 0.1 and 0.25) ceramics are prepared by a solid-state reaction method. It is clearly determined from XRD data that the characteristic peaks of Bi-2212 phase are observed in all samples. The resistivity measurements show that Tc (onset) values is gradually increasing as K content is increased. It is also found that K-Na co-doping influence the grain sizes for Bi-2212 phase significantly. The critical current densities as a function of magnetic field have been calculated from M-H hysteresis loops of samples according to Bean's critical model, indicating that K-Na co-doping cause higher Jc values than the pure ones.

  2. 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.

  3. 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

  4. Innovative processing of ceramic superconductors

    International Nuclear Information System (INIS)

    The discovery of high-temperature superconducting yttrium barium cuprate has changed the way we think about ceramics. It has broadened the perception and the definition of ceramic materials, and has attracted new workers from other fields such as chemistry, physics, and engineering, adding to the diversity of techniques used for synthesis and characterization. The authors are seeking to synthesize ceramics in a near-single-crystal configuration. They want to create a new class of material that may have wide-ranging applications, from sensors to optoelectronic devices to superconductive cables. This article I describes their approaches and some of preliminary results. A superconducting magnetic bearing and a high-current superconducting cable are possible applications of this work

  5. 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.

  6. 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.

  7. 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.

  8. Raman spectroscopy in YBa2Cu3O6+x and Bi2Sr2(CaxY1-x)Cu2O8+δ: pseudogap and superconducting gap

    International Nuclear Information System (INIS)

    We present results of Raman-scattering experiments in differently doped YBa2Cu3O6+x (Y-123) and Bi2Sr2(CaxY1-x)Cu2O8+δ (Bi-2212) single crystals. When reducing the doping level x the scattering intensity in B1g symmetry increases while it decreases in the B2g channel. This anisotropic behavior can be attributed to a qualitative change of the Fermi surface topology. At B2g symmetry we find evidence of a pseudogap Δ* in the normal state below a characteristic temperature T* ∼ 180 K. In the superconducting state, the spectra obtained from overdoped samples show the well-known pair-breaking (2Δ) features in both B1g and B2g symmetries while in the underdoped regime pair-breaking maxima can only be observed in the B2g channel. The magnitude of the gap can be estimated to be approximately 8kTc and is, from our experiments, different from Δ*. (orig.)

  9. 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.

  10. Superconductivity: materials and applications

    International Nuclear Information System (INIS)

    This digest paper presents the different types of superconducting materials: 1 - the low-TC superconductors: the multi-filament composite as elementary constituent, the world production of NbTi, the superconducting cables of the LHC collider and of the ITER tokamak; 2 - the high-TC superconductors: BiSrCaCuO (PIT 1G) ribbons and wires, deposited coatings; 3 - application to particle physics: the the LHC collider of the CERN, the LHC detectors; 4 - applications to thermonuclear fusion: Tore Supra and ITER tokamaks; 5 - NMR imaging: properties of superconducting magnets; 6 - applications in electrotechnics: cables, motors and alternators, current limiters, transformers, superconducting energy storage systems (SMES). (J.S.)

  11. Synthesis, electrical and thermal properties of Bi{sub 4}V{sub 2−x}Y{sub x}O{sub 11} (x=0.0 and 0.10) ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Sahu, S., E-mail: mroy1959@yahoo.co.in; Roy, M., E-mail: mroy1959@yahoo.co.in [Department of Physics, M. L. Sukhadia University, Udaipur-313002 (India)

    2014-04-24

    Polycrystalline ceramic samples of Bi{sub 4}V{sub 2−x}Y{sub x}O{sub 11} (x=0.0 and 0.10) have been synthesized by standard solid state reaction method. The formation of the compounds has been verified by room temperature (RT) X-ray diffraction. 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 = σ{sub o}exp(-Ea/kT). The specific heat and heat flow of both the compounds were determined as a function of temperature using Modulated Differential Scanning Calorimetry (MDSC)

  12. Synthesis, electrical and thermal properties of Bi{sub 4}V{sub 2-x}Zr{sub x}O{sub 11} (x=0.0 and 0.02) ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Sahu, S.; Jangid, S.; Roy, M. [Department of Physics, M. L. Sukhadia University, Udaipur-313002 (Rajasthan) (India); Barbar, S. K. [Center for Condensed Matter Sciences, National Taiwan University, Taipei-10617, Taiwan (China)

    2013-02-05

    Polycrystalline ceramic samples of Bi{sub 4}V{sub 2-x}Zr{sub x}O{sub 11} (x=0.0 and 0.02) have been synthesized by standard solid state reaction method. The formation of the compounds has been verified by room temperature (RT) X-ray diffraction. 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 {sigma} = {sigma}{sub Masculine-Ordinal-Indicator }exp)-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).

  13. Composition- and temperature-driven phase transition characteristics and associated electromechanical properties in Bi0.5Na0.5TiO3-based lead-free ceramics.

    Science.gov (United States)

    Bai, Wangfeng; Chen, Daqin; Zheng, Peng; Shen, Bo; Zhai, Jiwei; Ji, Zhenguo

    2016-05-17

    In this study, a lead-free ceramic system comprising (0.94 - x)Bi0.5Na0.5TiO3-0.06BaTiO3-xBi(Zn0.5Ti0.5)O3 (BNT-BT-BZT) was designed and prepared by a conventional solid-state reaction method. The effect of the addition of BZT on the phase transition characteristics and associated electromechanical properties of BNT-BT was systematically discussed and a schematic phase diagram was established. The addition of BZT had a strong impact on the phase transition as well as the strain and piezoelectric activity. The phase coexistence, which involves ferroelectric rhombohedral-relaxor pseudocubic phases, can be driven by modification with BZT and increases in temperature and can be confirmed by XRD measurements, analysis of Raman spectra and temperature-dependent changes in polarization and strain hysteresis loops. Accompanied by a shift in the ferroelectric-to-relaxor temperature TF-R to below room temperature on the addition of BZT, a compositionally induced ferroelectric-to-relaxor phase transition occurred, which gave rise to a large strain of 0.33% with a normalized strain Smax/Emax of 550 pm V(-1) at the critical BZT content x of 0.0275. The results were closely correlated with the composition and dependence on temperature of the phase transition, which significantly influenced the electromechanical properties, and the origin of the large strain observed in the present system was also addressed in detail. As a result, the design principles provided in this study open the possibility of obtaining BNT-based lead-free ceramics with enhanced electromechanical properties for actuator applications. PMID:27125262

  14. 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.

  15. Influence of local structural disorders on spectroscopic properties of multi-component CaF2-Bi2O3-P2O5-B2O3 glass ceramics with Cr2O3 as nucleating agent

    Science.gov (United States)

    Suresh, S.; Narendrudu, T.; Yusub, S.; Suneel Kumar, A.; Ravi Kumar, V.; Veeraiah, N.; Krishna Rao, D.

    2016-01-01

    Multi-component CaF2-Bi2O3-P2O5-B2O3 glasses doped with different concentrations of Cr2O3 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) and differential thermal analysis (DTA). Spectroscopic studies viz., optical absorption, Fourier transform infrared (FTIR), Raman and electron paramagnetic resonance (EPR) were carried out. The XRD, SEM and DTA studies indicated that the samples contain different crystalline phases. Results of optical absorption and EPR studies pointed out the gradual conversion of chromium ions from Cr3 + state to Cr6 + state with an increase of Cr2O3 content from 0.1 to 0.5 mol%. The results of FTIR, Raman and EPR studies revealed that Cr6 + ions participate in the glass network in tetrahedral positions and seemed to increase the polymerization of the glass ceramics. The quantitative analysis of results of the spectroscopic studies further indicated that the glasses crystallized with low concentration of Cr2O3 are favourable for solid state laser devices.

  16. 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.

  17. Structure and temperature dependent electrical properties of lead-free Bi/sub 0.5/Na/sub 0.5/TiO/sub 3/- SrZrO/sub 3/ ceramics

    International Nuclear Information System (INIS)

    Lead-free SrZrO/sub 3/-modified Bi/sub 0.5/ Na/sub 0.5/TiO/sub 3/ (BNT-SZ) ceramics were fabricated by a conventional solid state reaction method. X-ray diffraction analysis reveals a pure perovskite phase without any traces of secondary phases. Scanning electron microscopy images depicts dense grain morphology. The temperature dependences of the dielectric behavior was measured in the temperature range of 50-500 degree C at 100 kHz. With the increase in SZ content, the dielectric constant (er) constantly decreased and the maximum dielectric constant temperature (Tm) shifted towards lower temperatures. In addition to this, ferroelectric hysteresis loops indicated a disruption of ferroelectric order and increase in the relaxor character of BNT ceramics with increase in SZ concentration. A maximum values of remnant polarization (32 micro C/cm2) and piezoelectric constant (100 pC/N) were observed at SZ5 and SZ4, respectively. (author)

  18. Chemical and structural effects on the high-temperature mechanical behavior of (1−x)(Na1/2Bi1/2)TiO3-xBaTiO3 ceramics

    International Nuclear Information System (INIS)

    Bismuth sodium titanate–barium titanate [(1−x)(Na1/2Bi1/2)TiO3-xBaTiO3, NBT-100xBT] is one of the most well studied lead-free piezoelectric materials due in large part to the high field-induced strain attainable in compositions near the morphotropic phase boundary (x = 0.06). The BaTiO3-rich side of the phase diagram, however, has not yet been as comprehensively studied, although it might be important for piezoelectric and positive temperature coefficient ceramic applications. In this work, we present a thorough study of BaTiO3-rich NBT-100xBT by ferroelastic measurements, dielectric permittivity, X-ray diffraction, and Raman spectroscopy. We show that the high-temperature mechanical behavior, i.e., above the Curie temperature, TC, is influenced by local disorder, which appears also in pure BT. On the other hand, in NBT-100xBT (x < 1.0), lattice distortion, i.e., tetragonality, increases, and this impacts both the mechanical and dielectric properties. This increase in lattice distortion upon chemical substitution is counterintuitive by merely reasoning on the ionic size, and is due to the change in the A-O bond character induced by the Bi3+ electron lone pair, as indicated by Raman spectroscopy

  19. Chemical and structural effects on the high-temperature mechanical behavior of (1-x)(Na1/2Bi1/2)TiO3-xBaTiO3 ceramics

    Science.gov (United States)

    Deluca, Marco; Picht, Gunnar; Hoffmann, Michael J.; Rechtenbach, Annett; Töpfer, Jörg; Schader, Florian H.; Webber, Kyle G.

    2015-04-01

    Bismuth sodium titanate-barium titanate [(1-x)(Na1/2Bi1/2)TiO3-xBaTiO3, NBT-100xBT] is one of the most well studied lead-free piezoelectric materials due in large part to the high field-induced strain attainable in compositions near the morphotropic phase boundary (x = 0.06). The BaTiO3-rich side of the phase diagram, however, has not yet been as comprehensively studied, although it might be important for piezoelectric and positive temperature coefficient ceramic applications. In this work, we present a thorough study of BaTiO3-rich NBT-100xBT by ferroelastic measurements, dielectric permittivity, X-ray diffraction, and Raman spectroscopy. We show that the high-temperature mechanical behavior, i.e., above the Curie temperature, TC, is influenced by local disorder, which appears also in pure BT. On the other hand, in NBT-100xBT (x < 1.0), lattice distortion, i.e., tetragonality, increases, and this impacts both the mechanical and dielectric properties. This increase in lattice distortion upon chemical substitution is counterintuitive by merely reasoning on the ionic size, and is due to the change in the A-O bond character induced by the Bi3+ electron lone pair, as indicated by Raman spectroscopy.

  20. 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.

  1. Chemical and structural effects on the high-temperature mechanical behavior of (1−x)(Na{sub 1/2}Bi{sub 1/2})TiO{sub 3}-xBaTiO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Deluca, Marco [Materials Center Leoben Forschung GmbH, Roseggerstraße 12, 8700 Leoben (Austria); Institut für Struktur- und Funktionskeramik, Montanuniversitaet Leoben, Peter Tunner Straße 5, 8700 Leoben (Austria); Picht, Gunnar [Institute of Applied Materials, Ceramics in Mechanical Engineering, Karlsruhe Institute of Technology, 76131 Karlsruhe (Germany); Robert Bosch GmbH, Corporate Sector Research and Advance Engineering Applied Research 1, Robert Bosch Platz 1, 70839 Gerlingen (Germany); Hoffmann, Michael J. [Institute of Applied Materials, Ceramics in Mechanical Engineering, Karlsruhe Institute of Technology, 76131 Karlsruhe (Germany); Rechtenbach, Annett; Töpfer, Jörg [Department of SciTec, University of Applied Sciences Jena, Carl-Zeiß-Promenade 2, 07745 Jena (Germany); Schader, Florian H.; Webber, Kyle G., E-mail: webber@ceramics.tu-darmstadt.de [Institute of Materials Science, Technische Universität Darmstadt, 64287 Darmstadt (Germany)

    2015-04-07

    Bismuth sodium titanate–barium titanate [(1−x)(Na{sub 1/2}Bi{sub 1/2})TiO{sub 3}-xBaTiO{sub 3}, NBT-100xBT] is one of the most well studied lead-free piezoelectric materials due in large part to the high field-induced strain attainable in compositions near the morphotropic phase boundary (x = 0.06). The BaTiO{sub 3}-rich side of the phase diagram, however, has not yet been as comprehensively studied, although it might be important for piezoelectric and positive temperature coefficient ceramic applications. In this work, we present a thorough study of BaTiO{sub 3}-rich NBT-100xBT by ferroelastic measurements, dielectric permittivity, X-ray diffraction, and Raman spectroscopy. We show that the high-temperature mechanical behavior, i.e., above the Curie temperature, T{sub C}, is influenced by local disorder, which appears also in pure BT. On the other hand, in NBT-100xBT (x < 1.0), lattice distortion, i.e., tetragonality, increases, and this impacts both the mechanical and dielectric properties. This increase in lattice distortion upon chemical substitution is counterintuitive by merely reasoning on the ionic size, and is due to the change in the A-O bond character induced by the Bi{sup 3+} electron lone pair, as indicated by Raman spectroscopy.

  2. 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.

  3. What's hot in superconductivity at NRL

    International Nuclear Information System (INIS)

    The author reviews the latest results on the preparation and properties of the high superconducting transition temperature materials including some recent results on the Bi-Sr-Ca-Cu-O materials. Bulk, single crystal, and thin films are discussed

  4. Reproducible synthetic method for the topological superconductor CuxBi2Se3

    OpenAIRE

    Kondo, Ryusuke; Yoshinaka, Taiki; Imai, Yoshinori; Maeda, Atsutaka

    2013-01-01

    We report a reproducible synthetic method for superconducting Cu-intercalated Bi2Se3 by an improved melt growth method. Avoiding the production of Cu2Se, which has a higher melting point than that of Bi2Se3, and quenching Cu-Bi-Se mixtures at the liquid phase are keys to obtaining good superconducting samples in a reproducible manner.

  5. Liquid phase sintered superconducting cermet

    International Nuclear Information System (INIS)

    This patent describes a method of making a superconducting cermet having superconducting properties with improved bulk density, low porosity and in situ stabilization. It comprises: forming a structure of a superconducting ceramic material having the formula RM2Cu3O(6.5+x)wherein R is one or more rare earth elements capable of reacting to form a superconducting ceramic, M is one or more alkaline earth metal elements selected from barium and strontium capable of reacting to form a superconducting ceramic, x is greater than 0 and less than 0.5; and a precious metal compound in solid form selected from the class consisting of oxides, sulfides and halides of silver; and liquid phase sintering the mixture at a temperature wherein the precious metal of the precious metal compound is molten and below the melting point of the ceramic material. The liquid phase sintering is carried out for a time less than 36 hours but sufficient to improve the bulk density of the cermet

  6. 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

  7. Phase formation, structure and dielectric properties of ceramics (Na0.5Bi0.5)TiO3-(K0.5Na0.5)NbO3-BiFeO3

    Science.gov (United States)

    Kaleva, G. M.; Mosunov, A. V.; Sadovskaya, N. V.; Politova, E. D.; Stefanovich, S. Yu.

    2016-04-01

    Influence of BiFeO3 (BF) on phase formation, unit cell parameters, microstructure, dielectric and ferroelectric properties of solid solutions close to the morphotropic phase boundary in the (Na0.5Bi0.5)TiO3-(K0.5Na0.5)NbO3 system additionally modified by the low-melting KCl additives has been studied. The formation of pure perovskite structure samples decrease in the unit cell parameters and increase in the TC value stimulated by the BF addition have been revealed. It was proved that modification of compositions by small amounts of the BF and KCl additives leads to improvement of dielectric parameters.

  8. High temperature superconductivity from Russia

    CERN Document Server

    Larkin, AI

    1989-01-01

    This volume covers up-to-date ideas associated with the studies of high Tc superconductivity. Diverse theoretical points of view on the nature of this phenomenon are presented in the book. Experimental works discuss the results obtained in the studies of Bi and Tl superconductivity compounds as well as the thorough investigation of the different properties of 123 (YBaCu) compounds. Several articles are devoted to SQUIDs functioning at nitrogen temperatures and their application in research work.

  9. 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.)

  10. 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

  11. 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.

  12. Limits to the critical transport current in superconducting (Bi,Pb)2Sr2Ca2Cu3O10 silver-sheathed tapes: The railway-switch model

    International Nuclear Information System (INIS)

    We have proposed the ''railway-switch'' model to describe the superconducting transport current in (Bi,Pb)2Sr2Ca2Cu3O10 silver-sheathed tapes. The model assumes that in the textured polycrystalline filament the frequent small-angle c-axis tilt grain boundaries (''railway switches'') constitute strong links for the supercurrent. With the objective to identify the mechanisms that limit the critical-current density in the tapes we present measurements of the transport critical current normal to the tape plane and of the current-transfer length along the tape axis. From I-V curves we obtain the longitudinal critical-current distribution and compare it to the thickness variation of the filament. The experiments have been performed on monofilamentary powder-in-tube samples prepared in long lengths by rolling as the only tape-forming process. For all investigated samples the critical-current density at T=77 K in self-field was in the range jc=20--30 kA/cm2. We conclude that the dominant limitation for the transport critical current in the tapes is imposed by the low intragrain critical-current density jcc along the c axis (as compared to the in-plane critical-current density jcab) and by the even lower critical-current density jct across twist boundaries or intergrowths. Possibilities for an improvement of the performance of the (Bi,Pb)2Sr2Ca2Cu3O10 silver-sheathed tapes are discussed

  13. Superconducting critical state of Bi 2Sr 2CaCu 2O 8: Two-dimensional effects at low temperatures

    Science.gov (United States)

    Rodríguez, E.; Goffman, M. F.; Arribére, A.; de la Cruz, F.; Schneemeyer, L. F.

    1994-02-01

    The critical current in the c direction of Bi 2Sr 2CaCu 2O 8 is shown to increase with temperature in low temperature ZFC measurements. The results are consistent with a loss of the c direction long range phase correlation, induced by the temperature dependent critical current flowing in the ab planes. As a result of this and the loss of the long range correlation induced by thermal disorder, the low temperature electrical resistance of the ZFC critical state is finite at low temperatures, becomes zero and is finite again at higher temperature.

  14. Superconducting critical state of Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8]: two-dimensional effects at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, E. (Comision Nacional de Energia Atomica, Centro Atomico Bariloche (Argentina)); Goffman, M.F. (Comision Nacional de Energia Atomica, Centro Atomico Bariloche (Argentina)); Arribere, A. (Comision Nacional de Energia Atomica, Centro Atomico Bariloche (Argentina)); Cruz, F. de la (Comision Nacional de Energia Atomica, Centro Atomico Bariloche (Argentina)); Schneemeyer, L.F. (AT and T Bell Labs., Murray Hill, NJ (United States))

    1994-02-01

    The critical current in the c direction of Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8] is shown to increase with temperature in low temperature ZFC measurements. The results are consistent with a loss of the c direction long range phase correlation, induced by the temperature dependent critical current flowing in the ab planes. As a result of this and the loss of the long range correlation induced by thermal disorder, the low temperature electrical resistance of the ZFC critical state is finite at low temperatures, becomes zero and is finite again at higher temperature. (orig.)

  15. Superconducting critical state of Bi2Sr2CaCu2O8: two-dimensional effects at low temperatures

    International Nuclear Information System (INIS)

    The critical current in the c direction of Bi2Sr2CaCu2O8 is shown to increase with temperature in low temperature ZFC measurements. The results are consistent with a loss of the c direction long range phase correlation, induced by the temperature dependent critical current flowing in the ab planes. As a result of this and the loss of the long range correlation induced by thermal disorder, the low temperature electrical resistance of the ZFC critical state is finite at low temperatures, becomes zero and is finite again at higher temperature. (orig.)

  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. 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)

  19. 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)

  20. Superconductivity in the Sn-Ba-Sr-Y-Cu-O system

    Science.gov (United States)

    Aleksandrov, K. S.; Khrustalev, B. P.; Krivomazov, S. N.; Petrov, M. I.; Vasilyev, A. D.; Zwegintsev, S. A.

    1991-01-01

    After the discovery of high-T(sub c) superconductivity in the La-Ba-Cu-O compound, several families of superconducting oxides were synthesized. Here, researchers report the results of the search for superconductivity in the compounds based on tin which has a lone electron pair like Bi, Tl, and Pb. The following compounds were synthesized: Sn1Ba1Sr1Cu3O(sub x), Sn1Ba1Ca1Cu3O(sub x), Sn1Ba1Mg1Cu3O(sub x), Sn1Sr1Ca1Cu3O(sub x), Sn1Sr1Mg1Cu3O(sub x), and Sn1Ca1Mg1Cu3O(sub x). The initial components were oxides and carbonates of the appropriate elements. A standard firing-grinding procedure was used. Final heating was carried out at 960 C during 12 hours. Then the samples were cooled inside the furnace. All the synthesis cycles were carried out in air atmosphere. Among the synthesized compounds only Sn1Ba1Sr1Cu3O(sub x) showed remarkable conductivity. Other compounds were practically dielectrics. Presence of a possible superconductivity in Sn1Ba1Sr1Cu3O(sub x) was defined by using the Meissner effect. At low temperature a deviation from paramagnetic behavior is observed. The hysteresis loops obtained at lower temperature undoubtly testify to the presence of a superconductive phase in the sample. However, the part of the superconductive phase in the Sn1Ba1Sr1Cu3O(sub x) ceramic turned out to be small, less than 2 percent, which agrees with the estimation from magnetic data. In order to increase the content of the superconductive phase, two-valent cations Ba and Sr were partially substituted by univalent (K) and three-valent ones (Y).

  1. Structure, non-stoichiometry and thermodynamic properties of Bi1.85Sr2Co1.85O7.7−δ ceramics

    International Nuclear Information System (INIS)

    Highlights: • Cobaltite Bi1.85Sr2Co1.85O7.7−δ was prepared and its structure was refined. • Oxygen non-stoichiometry of Bi1.85Sr2Co1.85O7.7−δ was determined by TG. • Thermodynamic properties were measured by PPMS, DSC and drop calorimetry. • The heat capacity was analyzed using combined Debye–Einstein model. - Abstract: The structure and oxygen non-stoichiometry of misfit layered cobaltite Bi1.85Sr2Co1.85O7.7−δ was determined by Rietveld analysis and by thermogravimetric measurements. The heat capacity and enthalpy increments of pseudo-ternary oxide Bi1.85Sr2Co1.85O7.7−δ was measured by the relaxation time method (PPMS) from 2 K to 256 K, by differential scanning calorimetry (DSC) from 258 K to 355 K and by the drop calorimetry from 573 K to 1153 K. Above room temperature the temperature dependence of the molar heat capacity in the form Cpm = (305.8 + 0.07325 · T − 4702536 · T−2) J K−1 mol−1 was derived by the least-squares method from the experimental data. The heat capacity was analyzed in terms of a combined Debye–Einstein model. The molar entropy Sm∘(298.15)=317.7 J mol−1 K−1 was evaluated from the low temperature heat capacity measurements

  2. Investigation of the chemical composition of (Na{sub 1-x}Bi {sub x})(Mn {sub y}Nb{sub 1-y})O{sub 3} ceramics by single particle electron probe X-ray microanalysis with an application of Monte Carlo simulations

    Energy Technology Data Exchange (ETDEWEB)

    Spolnik, Z. [Department of Chemistry, University of Antwerp, Campus ' Drie Eiken' , Universiteitsplein 1, B-2610 Antwerp (Belgium)]. E-mail: zoya.spolnik@ua.ac.be; Osan, J. [KFKI Atomic Energy Research Institute, P.O. Box 49, H-1525 Budapest (Hungary); Klepka, M. [Polish Academy of Science, Insitute of Physics, Al. Lotnikow 32/46 PL-02668, Warsaw (Poland); Lawniczak-Jablonska, K. [Polish Academy of Science, Insitute of Physics, Al. Lotnikow 32/46 PL-02668, Warsaw (Poland); Van Grieken, R. [Department of Chemistry, University of Antwerp, Campus ' Drie Eiken' , Universiteitsplein 1, B-2610 Antwerp (Belgium); Molak, A. [Institute of Physics, University of Silesia, ul. Uniwersytecka 4, PL-40-007 Katowice (Poland); Potgieter, J.H. [School of Process and Materials Engineering, University of the Witwatersrand, Private Bag X3, Wits, 2050 (South Africa)

    2005-04-30

    Accurate estimation of the elemental composition of materials that contain both low- and high-Z elements by electron probe X-ray microanalysis is not an easy task. An example of this kind of material is a new family of ceramics with general formula (Na{sub 1-x}Bi{sub x})(Mn {sub y}Nb{sub 1-y})O{sub 3}. To solve this problem, a method based on Monte Carlo simulations combined with an iterative approximation, which was recently successfully applied to quantitative analysis of the elemental content in aerosol particles, was used. The quantification procedure was evaluated on Bi{sub 2}O{sub 3}, PbO{sub 2} and NaNbO{sub 3} particles from stoichiometric compounds and applied to check the homogeneity and elemental contents of the selected ceramic after the application of different heat treatments.

  3. 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

  4. Insulation coating of silver tapes using an organometallic solution of Zr and Ca for application to Bi-based superconductors

    International Nuclear Information System (INIS)

    Silver tapes were spray coated using an organometallic solution as the carrier liquid. When this solution was annealed in air at 825 deg C, ∼4% of its total weight remained as CaZrO3. Mixtures of Bi2O3, SrCO3 and CaCO3 have been prepared with seven different stoichiometries. An organometallic solution was mixed with ceramic oxide powders and spray coated onto silver tapes. Electrical insulation tests were performed applying a dc potential, and insulation survived more than 30 V. Coated tapes were coiled to progressively decreasing diameters down to 1 mm diameter with no sign of cracking, indicating the possibility of metallic bonding and diffusion. This technique appears to be suitable for use in the insulation of Bi-based superconducting tapes and wires, since it does not contain any element that is chemically reactive to this system

  5. Josephson junction using a crossed contact of superconducting Bi(Pb)-Sr-Ca-Cu-O thin film with 110 K-phase

    International Nuclear Information System (INIS)

    Bi1.75Pb0.17Sr2Ca2.1Cu3.2Oy thin films with zero resistivity at 115 K, were prepared by dc magnetron sputtering and subsequent high-temperature annealing. This paper reports that Josephson bridges were fabricated b crossed contact of two cleaved planes of the thin films. Self-induced current steps and multi photon-assisted tunneling currents due to quasi-particles tunneling across the oxide gap barriers was due to oxidation of the Cu component and the extrication of Ca near the crossed contact of the thin film by soaking the thin film in liquid nitrogen. It seems possible to fabricate smaller bridge with a single junction by the use of thinner as-grown films with smoother surfaces

  6. 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)

  7. 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)

  8. 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

  9. Synthesis and characterization of (Bi0.5Ba0.5) (Fe0.5Ti0.5) O3 ceramic

    International Nuclear Information System (INIS)

    Graphical abstract: Temperature variation of (a) dielectric constant (b) dielectric loss of the sample. - Highlights: • The high values of dielectric permittivity and low value of tangent loss. • It used for microwave applications. • The impedance and dielectric relaxation in the material is non exponential and non Debye-type. • Its ac conductivity obeys Jonscher universal power law. - Abstract: The polycrystalline sample of (Bi0.5Ba0.5) (Fe0.5Ti0.5) O3 (BF–BT) was prepared by a standard mixed oxide method. Analysis of room temperature XRD pattern and Raman/FTIR spectra of the compound does not exhibit any change in its crystal structure of BaTiO3 on addition of BiFeO3 in equal ratio. The surface morphology of the gold-plated sintered pellet sample recorded by SEM (scanning electron microscope) exhibits a uniform distribution of grains with less porosity. Detailed studies of nature and quantity of variation of dielectric constant, tangent loss, and polarization with temperature and frequency indicate the existence of ferroelectric phase transition at high-temperature. There is a low-temperature anti-ferromagnetic phase transition below 375 °C in the material. Detailed studies of electrical properties (impedance, modulus, etc.) of the material confirmed a strong correlation between micro-structure and properties

  10. 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

  11. 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)

  12. 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.

  13. 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.

  14. 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.

  15. Yttrium ceramics YBa2Cu3Oy (5,8 ≤ y ≤ 7,7): structure,superconductivity, phase diagrams

    International Nuclear Information System (INIS)

    T-y phase diagrams, electrophysical properties, structures and superstructures of all phases (OI,OII,OIII,TI,TII, etc.) in the YBa2Cu3Oy system (5,8 ≤ y ≤ 7,7) are considered. The formation of the phases under study is mainly determined by the charge in oxygen concentration in the basal plane. The YBa2Cu3O7,0 compound is found to be optimum for the occurrence of metal conductivity and high-temperature superconductivity, because with a great oxygen deficiency in YBa2Cu3O6,0 there are no oxygen ions in the basal plane whereas with oxygen excess in YBa2Cu3O7,7 the quantity of oxygen vacancies in the basal plane is insufficient. 155 refs., 3 tab., 28 figs

  16. Electromagnetic properties of Bi-2223/Ag concentric tapes

    International Nuclear Information System (INIS)

    It is well established that near the silver interface highly textured Bi-2223 layers compared to the inner ceramic core may be obtained. Thus Bi-2223 multilayered concentric tapes with silver matrix are very promising in increasing transport critical current densities. In the present work the authors report on the electromagnetic characterization of short tapes having in their cross-section a very thin HTS flattened ring with Ag inside and outside of it. The samples were prepared by the powder in tube method and have self-field critical current densities Jc of the order of 3 x 104 A/cm2 at 77 K. Transport and SQUID magnetization measurements revealed weak link nature of the samples in low magnetic fields. Large transport Jc(B) hysteresis was observed at 4.2 K and magnetic fields up to 20 T. Magnetic field profiles measurements with miniature Hall sensors are in qualitative accordance with model calculations supposing homogeneous current density distribution across the superconducting core

  17. 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.).

  18. Superconducting transistor

    Science.gov (United States)

    Gray, Kenneth E.

    1979-01-01

    A superconducting transistor is formed by disposing three thin films of superconducting material in a planar parallel arrangement and insulating the films from each other by layers of insulating oxides to form two tunnel junctions. One junction is biased above twice the superconducting energy gap and the other is biased at less than twice the superconducting energy gap. Injection of quasiparticles into the center film by one junction provides a current gain in the second junction.

  19. Superconducting technology

    International Nuclear Information System (INIS)

    Superconductivity has a long history of about 100 years. Over the past 50 years, progress in superconducting materials has been mainly in metallic superconductors, such as Nb, Nb-Ti and Nb3Sn, resulting in the creation of various application fields based on the superconducting technologies. High-Tc superconductors, the first of which was discovered in 1986, have been changing the future vision of superconducting technology through the development of new application fields such as power cables. On basis of these trends, future prospects of superconductor technology up to 2040 are discussed. In this article from the viewpoints of material development and the applications of superconducting wires and electronic devices. (author)

  20. 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)

  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. Interface superconductivity

    International Nuclear Information System (INIS)

    Highlights: • We discuss interfacial superconductivity, a field boosted by the discovery of the superconducting interface between LaAlO. • This system allows the electric field control and the on/off switching of the superconducting state. • We compare superconductivity at the interface and in bulk doped SrTiO. • We discuss the role of the interfacially induced Rashba type spin–orbit. • We briefly discuss superconductivity in cuprates, in electrical double layer transistor field effect experiments. • Recent observations of a high Tc in a monolayer of FeSe deposited on SrTiO3 are presented. - Abstract: Low dimensional superconducting systems have been the subject of numerous studies for many years. In this article, we focus our attention on interfacial superconductivity, a field that has been boosted by the discovery of superconductivity at the interface between the two band insulators LaAlO3 and SrTiO3. We explore the properties of this amazing system that allows the electric field control and on/off switching of superconductivity. We discuss the similarities and differences between bulk doped SrTiO3 and the interface system and the possible role of the interfacially induced Rashba type spin–orbit. We also, more briefly, discuss interface superconductivity in cuprates, in electrical double layer transistor field effect experiments, and the recent observation of a high Tc in a monolayer of FeSe deposited on SrTiO3

  4. High-Tc superconducting phases in bismuth cuprates with high content of Ca and Cu

    International Nuclear Information System (INIS)

    High-Tc superconductors with critical temperature Tc∼110K have been synthesized in Bi-Pb-Sr-Ca-Cu-O system. Effect of surplus Ca and Cu on Tc and phase content of the ceramics has been investigated. A possibility of obtaining phases with a greater, than in 2223, number of adjacent two-dimensional CuO2 layers is discussed. Suggestions are made about a possible mechanism for superconductivity in the system of bismuth cuprates. This mechanism presumes a pairing of free charge carriers in the neighbouring CuO2 planes mediated by an exchange-correlation hole which is produced by these carriers in a quasimetallic Ca layer separating the CuO2 planes. 18 refs.; 4 figs

  5. 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)

  6. 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)

  7. Quantum interference at direct current in ceramics YBa2Cu3O7-x

    International Nuclear Information System (INIS)

    The Josephson effects and quantum dc interference in superconducting ceramics YBa2Cu3O7-x having the superconducting transition temperature of 93 K are investigated experimentally. It is shown that along with the known quantum interference, observed in multilink samples of high-Tc superconducting ceramics and ac interference, in the superconducting ceramics there exists quantum interference which also occurs in one-coupled samples at direct current, the induction-voltage conversion steepness and the signal-noise ratio in the high-Tc superconducting ceramics at 77 K being commensurate with similar charateristics of classical dc squids operating at 4.2 K. It is found from the temperature dependence of the Josephson current in samples whose sizes are much greater than coherence lengths, that links in the ceramics with percolation paths of current flow refer to the SNS type percolation paths of current flow refer to the SNS type

  8. Structural Ceramics

    Science.gov (United States)

    1986-01-01

    This publication is a compilation of abstracts and slides of papers presented at the NASA Lewis Structural Ceramics Workshop. Collectively, these papers depict the scope of NASA Lewis' structural ceramics program. The technical areas include monolithic SiC and Si3N4 development, ceramic matrix composites, tribology, design methodology, nondestructive evaluation (NDE), fracture mechanics, and corrosion.

  9. 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.)

  10. Near-net-shape fabrication of continuous Ag-Clad Bi-Based superconductors

    International Nuclear Information System (INIS)

    We have developed a near-net-shape process for Ag-clad Bi-2212 superconductors as an alternative to the powder-in-tube process. This new process offers the advantages of nearly continuous processing, minimization of processing steps, reasonable ability to control the Bi-2212/Ag ratio, and early development of favorable texture of the Bi-2212 grains. Superconducting properties are discussed

  11. Study of structural, electrical, magnetic and optical properties of 0.65BaTiO3–0.35Bi0.5Na0.5TiO3–BiFeO3 multiferroic composite

    International Nuclear Information System (INIS)

    Highlights: • Prepared magnetoelectric composites (1 − x)[0.65BaTiO3–0.35Bi0.5Na0.5TiO3]–xBiFeO3. • Magnetic hysteresis measurement using SQUID shows the antiferromagnetic nature. • Antiferromagnetic nature was also confirmed by ZFC–FC curves. • Presence of magnetocapacitance depicts the magnetoelectric coupling in the sample. • Synthesized Composite ceramics shows NTC behavior analogous to a semiconductor. • Optical study shows band gap energies decreasing with increase of BiFeO3 content. - Abstract: Conventional solid state reaction method was used to prepare (1 − x)[0.65BaTiO3–0.35Bi0.5Na0.5TiO3]–xBiFeO3 [where x = 0.0, 0.10, 0.15 and 0.20] composite. The presence of constituent phases in composite was confirmed by X-ray diffraction (XRD) studies. Average grain size was calculated by using field effect scanning electron microscope (FESEM) which increases from 356 nm to 577 nm with increase in ferrite content. Dielectric study confirms the presence of both ferroelectric and ferrite phases. We also found that the dielectric constant (ε) and Curie temperature (Tc) for ferrite phase increases with increase in the BiFeO3 content. Remnant polarization and coercive field for 0.65BaTiO3–0.35Bi0.5Na0.5TiO3 are found to be 7.63 μC/cm2 and 9.55 kV/cm respectively, afterward these values decreases with increase in the ferrite content. Magnetic hysteresis were measured at temperature 300 K and 5 K using superconducting quantum interference device which shows that 0.65BaTiO3–0.35Bi0.5Na0.5TiO3–BiFeO3 has antiferromagnetic nature with unsaturated hysteresis loops so only able to obtain the magnetization (MH) at 7 T. The antiferromagnetic nature of composite ceramics was also confirmed from the ZFC–FC curve. The presence of magnetocapacitance depicts the magnetoelectric coupling at room temperature. Impedance analysis provides the evidence of space charge accumulation in the samples, which vanish at higher frequencies and temperature. The

  12. 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.

  13. Superconducting cavities

    International Nuclear Information System (INIS)

    The basic properties of superconducting cavities for electron accelerators are discussed with special emphasis on the following topics: technical motivation for the use of superconducting cavities; surface impedance; the critical field of superconductors; anomalous losses; materials other than niobium; technological achievements for accelerating cavities. (author)

  14. 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.

  15. 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)

  16. Interface superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Gariglio, S., E-mail: stefano.gariglio@unige.ch [DQMP, Université de Genève, 24 Quai E.-Ansermet, CH-1211 Genève (Switzerland); Gabay, M. [Laboratoire de Physique des Solides, Bat 510, Université Paris-Sud 11, Centre d’Orsay, 91405 Orsay Cedex (France); Mannhart, J. [Max Planck Institute for Solid State Research, 70569 Stuttgart (Germany); Triscone, J.-M. [DQMP, Université de Genève, 24 Quai E.-Ansermet, CH-1211 Genève (Switzerland)

    2015-07-15

    Highlights: • We discuss interfacial superconductivity, a field boosted by the discovery of the superconducting interface between LaAlO. • This system allows the electric field control and the on/off switching of the superconducting state. • We compare superconductivity at the interface and in bulk doped SrTiO. • We discuss the role of the interfacially induced Rashba type spin–orbit. • We briefly discuss superconductivity in cuprates, in electrical double layer transistor field effect experiments. • Recent observations of a high T{sub c} in a monolayer of FeSe deposited on SrTiO{sub 3} are presented. - Abstract: Low dimensional superconducting systems have been the subject of numerous studies for many years. In this article, we focus our attention on interfacial superconductivity, a field that has been boosted by the discovery of superconductivity at the interface between the two band insulators LaAlO{sub 3} and SrTiO{sub 3}. We explore the properties of this amazing system that allows the electric field control and on/off switching of superconductivity. We discuss the similarities and differences between bulk doped SrTiO{sub 3} and the interface system and the possible role of the interfacially induced Rashba type spin–orbit. We also, more briefly, discuss interface superconductivity in cuprates, in electrical double layer transistor field effect experiments, and the recent observation of a high T{sub c} in a monolayer of FeSe deposited on SrTiO{sub 3}.

  17. Melt processing of Bi--2212 superconductors using alumina

    Science.gov (United States)

    Holesinger, Terry G.

    1999-01-01

    Superconducting articles and a method of forming them, where the superconducting phase of an article is Bi.sub.2 Sr.sub.2 CaCu.sub.2 O.sub.y (Bi-2212). Alumina is combined with Bi-2212 powder or Bi-2212 precursor powder and, in order to form an intimate mixture, the mixture is melted and rapidly cooled to form a glassy solid. The glassy solid is comminuted and the resulting powder is combined with a carrier. An alternative to melting is to form the mixture of nanophase alumina and material having a particle size of less than about 10 microns. The powder, with the carrier, is melt processed to form a superconducting article.

  18. 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.

  19. 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.

  20. Superconducting device

    International Nuclear Information System (INIS)

    The present invention provides a superconducting device to be used in a thermonuclear device and capable of unifying a current distribution in a parallel superconducting main line without consumption of liquid helium caused by Joule loss. That is, the device has a paired coils comprising a coil comprising one of plurality of superconducting wires and another coil comprising the other of plurality of superconducting wires and having a reverse winding or negative mutual inductance relative to the coil. A circuit comprising a portion of a main line is disposed to the one coil of the paired coils, and a circuit comprising the remainder of the main line is connected to the other coil each in series. The circuit has a parallel constitution. Such a constitution can provide an effect of unifying the current distribution in the main line without consumption of liquid helium due to Joule loss. (I.S.)

  1. 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

  2. Effects of K doping on structural and superconducting properties of Bi{sub 1.5}Pb{sub 0.5}Sr{sub 1.8}CaCu{sub 2}O{sub 8+δ} compounds

    Energy Technology Data Exchange (ETDEWEB)

    Belala, K; Mosbah, M. F. [Material Sciences and Applications Research Unit, Physics Department, Constantine 1 University, B.P. 325 Route d' Ain El Bey, 25017 Constantine (Algeria)

    2013-12-16

    Two kinds of potassium doped Bi(Pb)2212 samples are used to investigate the effect of doping the Bi(Pb)2212 ((Bi,Pb){sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}) phase by potassium (K): In the first one K is substituted on the Sr site; In the second one K is added. Using the solid state method reaction samples of Bi{sub 1.5}Pb{sub 0.5}(Sr{sub 1.8−x}K{sub x})CaCu{sub 2}O{sub 8+d} and Bi{sub 1.5}Pb{sub 0.5}Sr{sub 1.8}CaCu{sub 2}O{sub 8+d}K{sub x} (0 ≤ x≤ 0.05) have been prepared from powders of carbonates and primary oxides having purity over 99%. The samples have been characterized by X ray diffraction (XRD), scanning electron microscopy (SEM) and resistivity versus temperature measurements. Results show how the kind and the rate of doping by potassium affects the structural and transport properties of Bi(Pb)2212 phase.

  3. 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...

  4. 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$^{−1}$).

  5. Study on the site preference of Ca in superconducting oxides Bi2Sr2−xCaxCuO6+δ (0.1 ≤ x ≤ 1.0)

    International Nuclear Information System (INIS)

    A series of compound with the nominal composition of Bi2Sr2−xCaxCuO6+δ (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0) were synthesized by the sol–gel method. Constituent phases and crystal structure of samples were analyzed by X-ray diffraction. It can be found that the Ca-doped Bi-2201 system was composed of Bi-2201 phase containing Ca and a small quantity of Bi16(Sr,Ca)14O38. For Bi-2201 unit cell containing Ca, chemical component and site preference of Ca atoms were characterized systematically by transmission electron microscopy. With the introduction of Ca atoms, Sr-sites have been occupied partially by Ca2+ in Bi-2201 unit cell, which leads to a decrease in the lattice parameters c and b of the Bi-2201 phase when the Ca-content x is below 0.6. Two types of new orthorhombic lattices are formed in the substitution. One is a lattice with space group Pma2 as the two nearest neighbor Sr-sites in the same Sr–O layer are occupied by Ca2+. Its lattice parameters can be characterized as a = 5.402 Å, b = 5.313 Å and c = 24.272 Å, respectively. When two nearest Sr ions of the second neighboring Sr–O layers are replaced by Ca2+ ions, the lattice with the space group Pmn21 can be formed. Its lattice parameters are close to that of the previous. The modulation vector is lying in the a*–c* plane in the two new orthorhombic lattices (Pma2 and Pmn21). Bi/Ca-2201 lattice (with Ca) and Bi-2201 lattice (without Ca) coexist in the same Bi2Sr2−xCaxCuO6+δ grain, which can be described as an intergrowth structure

  6. 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.

  7. 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.

  8. Preparation of high-temperature superconducting ceramics

    International Nuclear Information System (INIS)

    We have prepared samples of the family ABa2Cu3Ox (A=Y, Gd, Eu, Dy, Sm, Er). The powdered samples were characterized by X-ray diffraction at room temperature. We have also studied the effect of Fe impurities in YBa2Cu3Ox and EuBa2Cu3Ox. Moreover, single crystals of YBa2Cu3Ox and La(1-x)SrxCuO4 were grown using cooper oxide flux. (Author)

  9. 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...

  10. YBCO superconducting tapes by magnetron IBAD

    International Nuclear Information System (INIS)

    Full text: Large-scale commercial applications of high-temperature superconductors in power devices and systems operating at liquid nitrogen temperatures (77 K) require flexible wire or tape with high critical current density, Jc = 104 - 106 A cm-2, that can be sustained in moderate to high magnetic field, ie. ≤ 0.2 T for transmission cables, 2 - 4 T for motors and transformers, 2 - 10 T for energy storage devices and superconducting magnets. These requirements cannot be met with the silver-sheathed Bi-2223/Ag composite tapes because of inherent materials constraints (eg. low flux pinning, granularity) and various processing difficulties. Recent efforts to produce high-current YBCO superconducting tapes (YBa2Cu3O7/buffer/metal) based on high quality epitaxial c-axis YBa2Cu3O7 thin films deposited on buffered Ni-based alloy substrates have demonstrated Jc = 105 - 106 A cm-2 and unsurpassed magnetic field performance at 77 K. From an existing platform in ion beam and thin film technologies we are developing in situ processes to address scale-up issues to produce YBCO tape. Here we discuss the deposition by magnetron IBAD and the properties of YBCO tapes. Biaxially aligned YSZ and CeO2 buffer layers are deposited at room temperature on polished Hastelloy substrates. Epitaxial YBa2Cu3O7 thin films, 200 - 400 nm thick, are deposited at 750 deg C by sputtering a stoichiometric YBa2Cu3O7 ceramic target in an argon/oxygen plasma. X-ray θ-2θ diffraction, rocking curves (ω scans), φ scans and pole figures are used to determine the crystalline quality and biaxial alignment of films. Typical YSZ and CeO2 buffer layers have (111) poles in the direction of the ion beam (55 deg) and full width at half maximum FWHM = 24 - 30 deg. The YBCO tapes have (103) pole FWHM = 24 deg, Δω = 2 deg and Jc ∼ 3x105 A cm-2 at 77 K Similar YBa2Cu3O7 films deposited on MgO (100) substrates have Jc = (1 - 4)x106 A cm-2

  11. Ceramic Methyltrioxorhenium

    CERN Document Server

    Herrmann, R; Eickerling, G; Helbig, C; Hauf, C; Miller, R; Mayr, F; Krug von Nidda, H A; Scheidt, E W; Scherer, W; Herrmann, Rudolf; Troester, Klaus; Eickerling, Georg; Helbig, Christian; Hauf, Christoph; Miller, Robert; Mayr, Franz; Nidda, Hans-Albrecht Krug von; Scheidt, Ernst-Wilhelm; Scherer, Wolfgang

    2006-01-01

    The metal oxide polymeric methyltrioxorhenium [(CH3)xReO3] is an unique epresentative of a layered inherent conducting organometallic polymer which adopts the structural motifs of classical perovskites in two dimensions (2D) in form of methyl-deficient, corner-sharing ReO5(CH3) octahedra. In order to improve the characteristics of polymeric methyltrioxorhenium with respect to its physical properties and potential usage as an inherentconducting polymer we tried to optimise the synthetic routes of polymeric modifications of 1 to obtain a sintered ceramic material, denoted ceramic MTO. Ceramic MTO formed in a solvent-free synthesis via auto-polymerisation and subsequent sintering processing displays clearly different mechanical and physical properties from polymeric MTO synthesised in aqueous solution. Ceramic MTO is shown to display activated Re-C and Re=O bonds relative to MTO. These electronic and structural characteristics of ceramic MTO are also reflected by a different chemical reactivity compared with its...

  12. Magnetic properties of bi-, tri- and multicrystals of 3D topological insulator Bi1−x–Sbx(0.06⩽x⩽0.2)

    International Nuclear Information System (INIS)

    The magnetic properties of bi-, tri- and multicrystals of 3D topological insulator Bi1−xSbx(0.06c for one superconducting phase changes considerably, from 8.3 to 36 K, while for another superconducting phase, Tc remains within the range 3.7–4.6 K. In tricrystals and bicrystals with high contents of structural disorder and topological defects, ferromagnetic hysteresis loops and magnetic field expulsion have been observed simultaneously.

  13. Applied superconductivity. Vol. 1

    International Nuclear Information System (INIS)

    Since the discovery of of high-temperature superconducting (HTS) cuprates, R and D efforts were considerably accelerated. Besides the YBaCuO, Bi- and Tl-based high-temperature superconductors it is now known from recent experiments that Hg-Ba-Ca-Cu-1223 oxides become superconducting at 132 K and under pressure of 150 kbar, Tc of this 1223-high-temperature superconductor can be raised to 153 K. The technology for the processing of metallic low-temperature superconductors (LTS) on the basis of Nb-Ti and Nb3Sn is largely developed. These materials are widely used for magnetic resonance imaging and NMR spectroscopy. However a new challenge appears, namely complex system design, which requires creativity of scientists and engineers (e.g. magnets for fusion and accelerators). This holds a/o also for complex systems in LTS thin-film technology, where on the basis of Nb/Al-oxide/Nb junctions, sensors for bio-and geomagnetic measurements as well as nondestructive testing of materials or standards, e.g. voltage standards, were developed. In the area of digital LTS electronics, based on niobium technology, shift registers and onchip logic circuits were produced and operated up to clock frequencies of 20 GHz, simple RSFQ (rapid single flux quantum) devices even up to 100 GHz. The processing of long HTS wires and tapes is much more difficult. For Bi-2223 HTS, short-sample current carrying capabilities of about 80.000 A/cm2 at 77 K in zero magnetic field have been obtained. Wires up to 300 m long were manufactured, however with smaller critical currents. Furthermore we were learning the technology to produce bulk monolithic Y-Ba-Cu-O HTS by melt texturing. These materials are considered to be used in magnetic bearings or as permanent magnets, where at 65 K a field of 4 T could be reached (at the surface). (orig.)

  14. Superconducting magnets

    International Nuclear Information System (INIS)

    This report provides a self-consistent description of a magnetic field in the aperture of a superconducting magnet and details how this field can be calculated in a magnet with cos θ current distribution in the coils. A description of an apparatus that can be used to measure the field uniformity in the aperture has been given. Finally, a detailed description of the magnet being developed for use in the Superconducting Super Collider is given. When this machine is built, it will be by far the largest application of superconductivity to date and promises to make possible the experimental discoveries needed to understand the basic laws of nature governing the world in which we live

  15. Formation of low T/sub c/ superconducting phase in BSCCO system

    International Nuclear Information System (INIS)

    The sol spray process (modified form of sol gel) has been used to prepare Bi-Sr-Ca-Cu-O (BSCCO) homogeneous powder. In sol spray process, the prepared sol solutions have been dehydrated directly into BSCCO ceramic powder by spraying into a preheated temperature controlled pyrex glass column by means of compressed air atomization without the addition of organic chelating agent or organic templates. The prepared BSCCO material was characterized by thermogravimetric (TG), differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) techniques. Elemental compositions of BSCCO oxide powder and calcined pellet were verified by inductively coupled plasma emission spectrometer (ICP-OES) and electron probe micro analyzer (EPMA) attached with SEM. The results of these techniques were compared and correlated statistically. Student t-test and variance ratio test (F-test) were performed for the significance of results by analysis of variance (ANOVA). The dependence of electrical resistance versus temperature was recorded by classical four probe technique. It has been observed that sol spray process did affect the physico-chemical properties of BSCCO superconductor oxide. The superconducting phase identified by above mentioned techniques mainly shows the higher percentage of low T/sub c/ phase Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8/ (2212) with transition temperature of 85 K. (author)

  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. 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.

  18. 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.

  19. Ceramic glossary

    International Nuclear Information System (INIS)

    This book is a 2nd edition that contains new terms reflecting advances in high technology applications of ceramic materials. Definitions for terms which materials scientists, engineers, and technicians need to know are included

  20. Superconductive detectors

    International Nuclear Information System (INIS)

    Various attempts to use superconductors in the field of radiation detection are reviewed with particular emphasis on the stimulating perspectives offered by superconducting tunnel devices. Applications in the context of energy spectroscopy as well as in the fast discrimination are discussed in the light of recent results. In this framework the central role of nonequilibrium state of superconductors is analyzed in some detail. (orig.)