WorldWideScience

Sample records for gd-ba-cu-o high-temperature superconductor

  1. Advances in enlargement of melt-textured Gd-Ba-Cu-O superconductors

    International Nuclear Information System (INIS)

    Nariki, S; Sakai, N; Kita, M; Fujikura, M; Murakami, M; Hirabayashi, I

    2006-01-01

    We investigated the fabrication of melt-textured Gd-Ba-Cu-O bulk superconductors with the employment of a Gd 2 BaO 4 (Gd210)-BaCuO 2 -CuO precursor. This enabled us to synthesize a very large Gd-Ba-Cu-O bulk superconductor, 140 mm in diameter. The trapped field distribution measured at 77 K revealed that the sample had no serious cracks, and the maximum field was 2.3 T. The formation behaviour and depressing mechanism of cracking were studied using sintered Gd210-containing precursors. The Ba-Cu-O component in the precursor melted at around 900 deg. C. The formation of such a liquid phase enhanced the densification of the precursor by liquid phase sintering. The mechanical strength of the sintered precursor was increased compared to the conventional Gd123-Gd211 precursor. This will be effective in preventing crack formation in the texturing process of large single-grain samples. The superconducting properties of the bulk sample fabricated from Gd210-containing precursor have been discussed

  2. Processing of R-Ba-Cu-O superconductors

    International Nuclear Information System (INIS)

    Wu, H.

    1998-01-01

    Precipitation processes were developed to introduce second phases as flux pinning centers in Gd-Ba-Cu-O and Nd-Ba-Cu-O superconductors. In Gd-Ba-Cu-O, precipitation is caused by the decrease of the upper solubility limit of Gd 1+x Ba 2-x Cu 3 O 7 solid solution (Gd123ss) in low oxygen partial pressure. Processing of supersaturated Gd 1.2 Ba 1.8 Cu 3 O 7 in low oxygen partial pressure can produce dispersed second phases. Gd211 is formed as a separate phase while extensive Gd124 type stacking fault is formed instead of a separate CuO phase. As a result of the precipitation reaction, the transition temperature and critical current density are increased. In Nd-Ba-Cu-O, precipitation is caused by the decrease of the lower solubility limit of Nd 1+x Ba 2-x Cu 3 O 7 solid solution (Nd123ss) in oxygen. DTA results reveal the relative stability of Nd123ss in different oxygen partial pressures. In 1 bar oxygen partial pressure, Nd123ss with x = 0.1 is the most stable phase. In lower oxygen partial pressures, the most stable composition shifts towards the stoichiometric composition. The relative stability changes faster with decreasing oxygen partial pressure. Therefore, processing in oxygen and air tends to produce broad superconducting transitions but sharp transitions can be achieved in 0.01 bar and 0.001 bar oxygen partial pressures. While the lower solubility limits in 0.01 bar and 0.001 bar oxygen partial pressures remain at x = 0.00, the solubility limits in oxygen and air show a narrowing with decreasing temperature. Because of the narrowing of the solubility range in oxygen, oxygen annealing of Nd123 initially processed in low oxygen partial pressures will result in precipitation of second phases. The equilibrium second phase is BaCuO 2 for temperature above 608 C, and at lower temperatures the equilibrium second phases are Ba 2 CuO 3.3 and Ba 2 Cu 3 O 5+y . However, annealing at low temperature may produce a fine metastable transition phase. A coherent intermediate

  3. Effect of silver addition on the mechanical and field trapping properties of Gd-Ba-Cu-O bulk superconductors

    CERN Document Server

    Nariki, S; Matsui, M; Murakami, M

    2002-01-01

    The effect of Ag addition on the microstructure and the mechanical and field trapping properties of Gd-Ba-Cu-O bulk superconductor has been investigated. The single grain Gd-Ba-Cu-O bulk superconductors 32 mm in diameter were fabricated with 0-30 mass%Ag/sub 2/O additions by the melt growth method under controlled oxygen partial pressure of 1.0%. From microscopic observations, it was found that the macro- cracks in the a-b plane decreased with Ag addition. The three-point bending test showed that the average strength of Ag-free bulk was 69 MPa at room temperature, while the strength was dramatically improved to 110-115 MPa with 10-30 mass%Ag/sub 2/O additions. The trapped magnetic field of Ag-free bulk sample was 1.3 T at 77 K. The trapped field of bulk Gd-Ba-Cu-O samples with 10-20 mass%Ag/sub 2/O exhibited high values of 1.8-2.0 T at 77 K. However, the trapped field of the sample with 30 mass%Ag/sub 2/O addition was lowered to 1.1 T with decreasing the critical current density. The trapped field of Ag- adde...

  4. Recent progress in material technology on RE-Ba-Cu-O bulk superconductors

    International Nuclear Information System (INIS)

    Teshima, Hidekazu; Morita, Mitsuru

    2011-01-01

    The current status of large-grained RE-Ba-Cu-O (RE: Y or rare earth elements) bulk superconductors with excellent superconducting properties is described. Gd-Ba-Cu-O bulk superconductors can trap a very high magnetic field even if they are melt-processed in air. Although the electromagnetic force caused by the trapped field is larger for a larger sample and may break the sample, a large sample of Gd-Ba-Cu-O 46 mm in diameter has the potential of trapped magnetic fields greater than 10 T at around 40 K. In addition, single-grained bulk superconductors as large as 150 mm can be obtained using the RE compositional gradient method. Dy-Ba-Cu-O is an ideal material for current leads because it has low thermal conductivity and high critical current density at 77 K in high magnetic fields. Eu-Ba-Cu-O has low magnetic permeability, and is therefore suitable for bulk NMR applications. Progress in machining technology has made possible various bulk superconductors with complicated shapes such as coils, leading to small and strong electromagnets by stacking several coil-shaped bulk superconductors together. (author)

  5. Phonon modes in Gd1-xCexBa2Cu3O7-δ

    Directory of Open Access Journals (Sweden)

    SH Mozaffari

    2009-08-01

    Full Text Available  XRD and Raman analyses were performed to probe the phase formation and the variation of the normal phonon frequencies of the high temperature superconductor GdBa2Cu3O7-δ upon Ce doping. It was found that in addition to the orthorhombic 123 phase, some nonsuperconducting peaks, which are mainly due to the BaCeO3 secondary phase, are also formed that suppress the superconducting transition temperature. Besides, analysis of the Raman peaks shows that substitutions of Ce for Gd in GdBa2Cu3O7-δ are restricted to low concentrations in favor of impurity island formation .

  6. Pulsed Field Waveforms for Magnetization of HTS Gd-Ba-Cu-O Bulk Magnets

    International Nuclear Information System (INIS)

    Ida, T; Matsuzaki, H; Morita, E; Sakashita, H; Harada, T; Ogata, H; Kimura, Y; Miki, M; Kitano, M; Izumi, M

    2006-01-01

    Progress in pulse magnetization technique for high-temperature superconductor bulks of melt-textured RE-Ba-Cu-O with large diameter is important for the realization of power applications. We studied the pulsed power source and pulsed field waveforms to enhance to improve the magnetization properties for Gd-Ba-Cu-O bulk. The risetime and duration of pulse waveform effectively varied distribution of magnetic flux

  7. Melt-processed Gd-Ba-Cu-O superconductor with trapped field of 3 T at 77 K

    International Nuclear Information System (INIS)

    Nariki, S; Sakai, N; Murakami, M

    2005-01-01

    We fabricated a single-domain Gd-Ba-Cu-O bulk superconductor 65 mm in diameter and studied the microstructure, superconducting and field-trapping properties. Melt-processing was performed under a controlled oxygen partial pressure of 1.0% using a precursor containing Gd123 and Gd211 powders in a molar ratio of 2:1, with 0.5 wt% of Pt and 20 wt% of Ag 2 O added. The distribution of Ag and Gd211 particles was almost homogeneous. The addition of Ag was very effective in reducing the amount of cracking in the sample. The maximum trapped magnetic field recorded was 3.05 T at 77 K. We also measured the trapped field between two Gd-Ba-Cu-O bulk samples in order to minimize the demagnetizing effect and found that the trapped field reached 4.3 T at 77 K

  8. High critical currents in heavily doped (Gd,Y)Ba2Cu3Ox superconductor tapes

    International Nuclear Information System (INIS)

    Selvamanickam, V.; Gharahcheshmeh, M. Heydari; Xu, A.; Galstyan, E.; Delgado, L.; Cantoni, C.

    2015-01-01

    REBa 2 Cu 3 O x ((REBCO), RE = rare earth) superconductor tapes with moderate levels of dopants have been optimized for high critical current density in low magnetic fields at 77 K, but they do not exhibit exemplary performance in conditions of interest for practical applications, i.e., temperatures less than 50 K and fields of 2–30 T. Heavy doping of REBCO tapes has been avoided by researchers thus far due to deterioration in properties. Here, we report achievement of critical current densities (J c ) above 20 MA/cm 2 at 30 K, 3 T in heavily doped (25 mol. % Zr-added) (Gd,Y)Ba 2 Cu 3 O x superconductor tapes, which is more than three times higher than the J c typically obtained in moderately doped tapes. Pinning force levels above 1000 GN/m 3 have also been attained at 20 K. A composition map of lift factor in J c (ratio of J c at 30 K, 3 T to the J c at 77 K, 0 T) has been developed which reveals the optimum film composition to obtain lift factors above six, which is thrice the typical value. A highly c-axis aligned BaZrO 3 (BZO) nanocolumn defect density of nearly 7 × 10 11  cm −2 as well as 2–3 nm sized particles rich in Cu and Zr have been found in the high J c films

  9. Influence of the size of Gd211 starting powder on the critical current density of Gd-Ba-Cu-O bulk superconductor

    International Nuclear Information System (INIS)

    Nariki, S.; Seo, S.J.; Sakai, N.; Murakami, M.

    2000-01-01

    The relationship between the particle size of Gd211 powder in the precursor and the particle size of Gd211 inclusions in Gd-Ba-Cu-O bulk has been investigated. Gd211 starting powders with various diameters were prepared by the calcination of Gd 2 O 3 , BaO 2 and CuO powders at different temperatures between 800 and 1000 deg. C. The particle size of Gd211 in the melt-grown bulk was proportional to the particle size of the initial Gd211 powder. In conclusion, the employment of fine Gd211 powder led to a size reduction of 211 particles in the bulk, while largely enhancing the J c values in low magnetic fields. A large Gd-Ba-Cu-O/Ag bulk sample, 32 mm in diameter, could also be fabricated by the hot-seeding method. The maximum trapped field value revealed 1.5 T at 77 K. (author)

  10. High critical currents in heavily doped (Gd,Y)Ba{sub 2}Cu{sub 3}O{sub x} superconductor tapes

    Energy Technology Data Exchange (ETDEWEB)

    Selvamanickam, V., E-mail: selva@uh.edu; Gharahcheshmeh, M. Heydari; Xu, A.; Galstyan, E.; Delgado, L. [Department of Mechanical Engineering and Texas Center for Superconductivity, University of Houston, 4800 Calhoun Rd., Houston, Texas 77204-4006 (United States); Cantoni, C. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37381 (United States)

    2015-01-19

    REBa{sub 2}Cu{sub 3}O{sub x} ((REBCO), RE = rare earth) superconductor tapes with moderate levels of dopants have been optimized for high critical current density in low magnetic fields at 77 K, but they do not exhibit exemplary performance in conditions of interest for practical applications, i.e., temperatures less than 50 K and fields of 2–30 T. Heavy doping of REBCO tapes has been avoided by researchers thus far due to deterioration in properties. Here, we report achievement of critical current densities (J{sub c}) above 20 MA/cm{sup 2} at 30 K, 3 T in heavily doped (25 mol. % Zr-added) (Gd,Y)Ba{sub 2}Cu{sub 3}O{sub x} superconductor tapes, which is more than three times higher than the J{sub c} typically obtained in moderately doped tapes. Pinning force levels above 1000 GN/m{sup 3} have also been attained at 20 K. A composition map of lift factor in J{sub c} (ratio of J{sub c} at 30 K, 3 T to the J{sub c} at 77 K, 0 T) has been developed which reveals the optimum film composition to obtain lift factors above six, which is thrice the typical value. A highly c-axis aligned BaZrO{sub 3} (BZO) nanocolumn defect density of nearly 7 × 10{sup 11 }cm{sup −2} as well as 2–3 nm sized particles rich in Cu and Zr have been found in the high J{sub c} films.

  11. Characterization of the insulator barrier and the superconducting transition temperature in GdBa2Cu3O7−δ/BaTiO3 bilayers for application in tunnel junctions

    International Nuclear Information System (INIS)

    Navarro, H.; Sirena, M.; Haberkorn, N.; Yang, Ilkyu; Kim, Jeehoon

    2015-01-01

    The optimization of the superconducting properties in a bottom electrode and the quality of an insulator barrier are the first steps in the development of superconductor/insulator/superconductor tunnel junctions. Here, we study the quality of a BaTiO 3 tunnel barrier deposited on a 16 nm thick GdBa 2 Cu 3 O 7−δ thin film by using conductive atomic force microscopy. We find that the tunnel current is systematically reduced (for equal applied voltage) by increasing the BaTiO 3 barrier thickness between 1.6 and 4 nm. The BaTiO 3 layers present an energy barrier of ≈1.2 eV and an attenuation length of 0.35–0.5 nm (depending on the applied voltage). The GdBa 2 Cu 3 O 7−δ electrode is totally covered by a BaTiO 3 thickness above 3 nm. The presence of ferroelectricity was verified by piezoresponse force microscopy for a 4 nm thick BaTiO 3 top layer. The superconducting transition temperature of the bilayers is systematically suppressed by increasing the BaTiO 3 thickness. This fact can be associated with stress at the interface and a reduction of the orthorhombicity of the GdBa 2 Cu 3 O 7−δ . The reduction in the orthorhombicity is expected by considering the interface mismatch and it can also be affected by reduced oxygen stoichiometry (poor oxygen diffusion across the BaTiO 3 barrier)

  12. High critical currents in heavily doped (Gd,Y)Ba2Cu3Ox superconductor tapes

    Energy Technology Data Exchange (ETDEWEB)

    Selvamanickam, V; Gharahcheshmeh, MH; Xu, A; Galstyan, E; Delgado, L; Cantoni, C

    2015-01-19

    REBa2Cu3Ox ((REBCO), RE = rare earth) superconductor tapes with moderate levels of dopants have been optimized for high critical current density in low magnetic fields at 77 K, but they do not exhibit exemplary performance in conditions of interest for practical applications, i.e., temperatures less than 50K and fields of 2-30 T. Heavy doping of REBCO tapes has been avoided by researchers thus far due to deterioration in properties. Here, we report achievement of critical current densities (J(c)) above 20 MA/cm(2) at 30 K, 3 T in heavily doped (25 mol.% Zr-added) (Gd,Y)Ba2Cu3Ox superconductor tapes, which is more than three times higher than the J(c) typically obtained in moderately doped tapes. Pinning force levels above 1000 GN/m(3) have also been attained at 20 K. A composition map of lift factor in J(c) (ratio of J(c) at 30 K, 3 T to the J(c) at 77 K, 0 T) has been developed which reveals the optimum film composition to obtain lift factors above six, which is thrice the typical value. A highly c-axis aligned BaZrO3 (BZO) nanocolumn defect density of nearly 7 x 10(11) cm(-2) as well as 2-3 nm sized particles rich in Cu and Zr have been found in the high J(c) films. (C) 2015 AIP Publishing LLC.

  13. Improvement of the field-trapping capabilities of bulk Nd Ba Cu O superconductors using Ba Cu O substrates

    Science.gov (United States)

    Matsui, Motohide; Nariki, Shinya; Sakai, Naomichi; Iwafuchi, Kengo; Murakami, Masato

    2006-07-01

    We used Ba-Cu-O substrates to fabricate bulk Nd-Ba-Cu-O superconductors using a top-seeded melt-growth method. There were several advantages for the use of Ba-Cu-O substrate compared to conventional substrate materials such as MgO, ZrO2, Al2O3, RE123 and RE211 (RE = rare earth). The Ba-Cu-O did not react with the precursor and minimized liquid loss. Accordingly, the introduction of large-sized cracks was suppressed. We also found that Tc values were high at the bottom regions, which was ascribed to the beneficial effect of Ba-Cu-O in suppressing Nd/Ba substitution. As a result, we obtained bulk Nd-Ba-Cu-O superconductors that exhibited fairly good field-trapping capabilities, even at the bottom surfaces.

  14. Simple die pressing for making artificial holes in single-grain Gd1.5Ba2Cu3O7−y superconductors

    International Nuclear Information System (INIS)

    Kim, K-M; Park, S-D; Jun, B-H; Kim, C-J; Ko, T K

    2012-01-01

    The presence of artificial holes in single-grain REBa 2 Cu 3 O 7−y (RE123, RE: rare-earth elements) bulk superconductors can facilitate oxygen diffusion into superconducting grains through the increased surface area. In addition to the enhancement of oxygen diffusion, the mechanical properties and thermal conductivity of bulk superconductors can be improved by filling holes with a metallic conductive phase. This study presents a new and simple hole-making process for single-grain RE123 bulk superconductors. Artificial holes 3 or 5 mm in diameter were made for Gd 1.5 Ba 2 Cu 3 O 7−y (Gd1.5) powder compacts prior to the sintering/melt growth process using specially designed pressing dies. The die pressing neither induced cracking in powder compacts nor influenced thermal procedures for the Gd123 growth. Single-grain Gd1.5 bulk superconductors with holes were successfully fabricated by a top-seeded melt growth (TSMG) process using Gd1.5 powder compacts with holes. The die pressing was proven as a time-saving process in comparison with the conventional method which makes holes in sintered or melt-processed hard bodies by mechanical drilling. The detailed fabrication process of single-grain Gd1.5 bulk superconductor with holes, magnetic levitation forces, and magnetic flux density, estimated for the single-grain Gd123 bulk superconductors with holes, are reported. (paper)

  15. Temperature dependence of positron annihilation parameters in Tl-Ba-Ca-Cu-O superconductors

    International Nuclear Information System (INIS)

    Sundar, C.S.; Bharathi, A.; Ching, W.Y.; Jean, Y.C.; Hor, P.H.; Meng, R.L.; Huang, Z.J.; Chu, C.W.

    1990-01-01

    The results of positron lifetime and Doppler broadened line-shape parameter measurements as a function of temperature, across T c , in the Tl-Ba-Ca-Cu-O superconductors are presented. The bulk lifetime in the normal state is found to decrease with the increase in the number of CuO 2 layers. Different temperature dependencies of the annihilation parameters are observed in the various Tl systems containing different numbers of CuO 2 layers. In the Tl 2 Ba 2 Ca 2 Cu 3 O 10 system, an increase in lifetime is observed below T c , whereas in Tl 2 Ba 2 CaCu 2 O 8 , a decrease in lifetime is seen below T c . In the Tl 2 Ba 2 CuO 6 system, the lifetime is observed to be temperature independent. The different temperature variations of positron annihilation parameters are discussed in the light of the positron density distribution, obtained with use of the results of the self-consistent orthogonalized linear combination of atomic orbitals band-structure calculations. It is argued that the different temperature dependencies of the annihilation parameters is related to the positron density distribution within the unit cell and arise due to local charge transfer in the vicinity of the CuO 2 layer in the superconducting state

  16. Characterization of the insulator barrier and the superconducting transition temperature in GdBa{sub 2}Cu{sub 3}O{sub 7−δ}/BaTiO{sub 3} bilayers for application in tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Navarro, H., E-mail: henrynavarro@cab.cnea.gov.ar; Sirena, M.; Haberkorn, N. [Instituto Balseiro, Universidad Nacional de Cuyo and CNEA, 8400 Bariloche (Argentina); Centro Atómico Bariloche, Comisión Nacional de Energía Atómica. Av. Bustillo 9500, 8400 San Carlos de Bariloche (Argentina); Yang, Ilkyu [Department of Physics, Pohang University of Science and Technology, Pohang (Korea, Republic of); Kim, Jeehoon [Department of Physics, Pohang University of Science and Technology, Pohang (Korea, Republic of); CALDES, Institute for Basic Science, Pohang (Korea, Republic of)

    2015-07-28

    The optimization of the superconducting properties in a bottom electrode and the quality of an insulator barrier are the first steps in the development of superconductor/insulator/superconductor tunnel junctions. Here, we study the quality of a BaTiO{sub 3} tunnel barrier deposited on a 16 nm thick GdBa{sub 2}Cu{sub 3}O{sub 7−δ} thin film by using conductive atomic force microscopy. We find that the tunnel current is systematically reduced (for equal applied voltage) by increasing the BaTiO{sub 3} barrier thickness between 1.6 and 4 nm. The BaTiO{sub 3} layers present an energy barrier of ≈1.2 eV and an attenuation length of 0.35–0.5 nm (depending on the applied voltage). The GdBa{sub 2}Cu{sub 3}O{sub 7−δ} electrode is totally covered by a BaTiO{sub 3} thickness above 3 nm. The presence of ferroelectricity was verified by piezoresponse force microscopy for a 4 nm thick BaTiO{sub 3} top layer. The superconducting transition temperature of the bilayers is systematically suppressed by increasing the BaTiO{sub 3} thickness. This fact can be associated with stress at the interface and a reduction of the orthorhombicity of the GdBa{sub 2}Cu{sub 3}O{sub 7−δ}. The reduction in the orthorhombicity is expected by considering the interface mismatch and it can also be affected by reduced oxygen stoichiometry (poor oxygen diffusion across the BaTiO{sub 3} barrier)

  17. Vibrational spectra and lattice instabilities in the high-T/sub c/ superconductors YBa2Cu3O7 and GdBa2Cu3O7

    International Nuclear Information System (INIS)

    Bozovic, I.; Mitzi, D.; Beasley, M.

    1987-01-01

    The exceptionally high T/sub c/ of layered cuprates was proposed recently as originating from electronically driven structural instabilities. We have studied the infrared and Raman spectra of YBa 2 Cu 3 O/sub 7-//sub δ/ and GdBa 2 Cu 3 O/sub 7-//sub δ/ over a broad range of temperatures, from 10 to 300 K. We observed neither mode softening nor any other spectroscopic signature of lattice instabilities

  18. Deformation of high-temperature superconductors

    International Nuclear Information System (INIS)

    Goretta, K.C.; Routbort, J.L.; Miller, D.J.; Chen, N.; Dominguez-Rodriguez, A.; Jimenez-Melendo, M.; De Arellano-Lopez, A.R.

    1994-08-01

    Of the many families of high-temperature superconductors, only the properties of those discovered prior to 1989 - Y-Ba-Cu-O, Tl-Ba(Sr)-Ca-Cu-O, and Bi(Pb)-Sr-Ca-Cu-O - have been studied extensively. Deformation tests have been performed on YBa 2 Cu 3 O x (Y-123), YBa 2 Cu 4 O x (Y-124), TlBa 2 Ca 2 Cu 3 O x (Bi-2223). The tests have revealed that plasticity is generally limited in these compounds and that the rate-controlling diffusional kinetics for creep are very slow. Nevertheless, hot forming has proved to be quite successful for fabrication of bulk high-temperature superconductors, so long as deformation rates are low or large hydrostatic stresses are applied. Steady-state creep data have proved to be useful in designing optimal heat treatments for superconductors and in support of more-fundamental diffusion experiments. The high-temperature superconductors are highly complex oxides, and it is a challenge to understand their deformation responses. In this paper, results of interest and operant creep mechanisms will be reviewed

  19. Enhanced flux pinning by BaZrO3 and (Gd,y)2O3 nano-structures in metal organic chemical vapor deposited GdYBCO high temperature superconductor tapes

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y [SuperPower Incorporated, Schenectady, New York; Selvamanickam, V. [SuperPower Incorporated, Schenectady, New York; Paranthaman, Mariappan Parans [ORNL; Cantoni, Claudia [ORNL; Aytug, Tolga [ORNL; Goyal, Amit [ORNL; Lee, Dominic F [ORNL; Specht, Eliot D [ORNL; Zuev, Yuri L [ORNL; Zhang, Yifei [ORNL

    2009-01-01

    We have formed BaZrO3 nano-columns and (Gd,Y)2O3 nano-precipitates in reel-to-reel MOCVD processed (Gd,Y)Ba2Cu3O7-x coated conductors and increased the critical currents (Ic) of the conductors in applied magnetic fields to remarkable levels. A (Gd,Y)Ba2Cu3O7-x tape of 1m length with 6.5% Zr-additions and 30% composition rich in both Gd and Y showed Ic values of 813 A/cm-width at (self-field, 77K) and above 186 A/cm-width at (1T, 77K). The strongly enhanced flux pinning over a wide range of magnetic field orientations can be attributed to the bidirectionally aligned defect structures of BaZrO3 and (Gd,Y)2O3 created by optimized MOCVD conditions.

  20. The Effects of Gd-Free Impurity Phase on the Aging Behavior for the Microwave Surface Resistance of Ag-coated GdBa2Cu3O7-δ at Cryogenic Temperatures

    Science.gov (United States)

    Lee, Sungho; Yang, Woo Il; Jung, Ho Sang; Oh, Won-Jae; Jang, Jiyeong; Lee, Jae-Hun; Kang, Kihyeok; Moon, Seung-Hyun; Yoo, Sang-Im; Lee, Sang Young

    2018-05-01

    High-T C GdBa2Cu3O7-δ (GdBCO) superconductor has been popular for making superconductive tapes that have much potential for various fields of large-scale applications. We investigated aging effects on the microwave surface resistance (R S) of Ag-coated GdBCO layer on Hastelloy substrate, so called GdBCO coated conductors (CCs), and Ag-coated GdBCO films on LaAlO3 (LAO) single-crystal substrates at cryogenic temperatures and compared them with each other. Unlike the R S of Ag-coated GdBCO films showing significant degradation in 4 weeks, no significant aging effects were found in our Ag-coated GdBCO CCs aged 85 weeks. The reactive co-evaporation deposition and reaction (RCE-DR) method was used for preparing the Ag-coated GdBCO CCs. Such durability of the Ag-coated GdBCO CCs in terms of the R S could be explained by existence of a protective impurity phase, i.e., Gd-free Ba-Cu-O phase as confirmed by transmission electron microscopy study combined with the energy-dispersive X-ray spectroscopy measurements. Although the scope of this study is limited to the Ag-coated GdBCO CCs prepared by using the RCE-DR method, our results suggest that a solution for preventing the aging effects on transport properties of other kinds of Ag-coated GdBCO CCs could be realized by means of an artificially-grown protective impurity layer.

  1. Development of a generic seed crystal for the fabrication of large grain (RE)-Ba-Cu-O bulk superconductors

    International Nuclear Information System (INIS)

    Shi, Y; Babu, N Hari; Cardwell, D A

    2005-01-01

    The critical current density, J c , irreversibility field, B irr , and magnetic field trapping ability of (LRE)-Ba-Cu-O bulk superconductors, where LRE is a light rare earth element such as Nd, Sm, Eu and Gd, are generally superior to those of the more common melt-processed Y-Ba-Cu-O (YBCO). The lack of availability of a suitable seed crystal to grow large, single grain (LRE)-Ba-Cu-O superconductors with controlled orientation, however, has hindered severely the development of these materials for engineering applications over the past ten years. In this communication we report for the first time the development of a generic seed crystal that can be used to fabricate any rare earth (RE) based (RE)-Ba-Cu-O ((RE)BCO) superconductor in the form of a large single grain with controlled orientation. The new seed crystal will potentially enable large grain (LRE)-Ba-Cu-O bulk superconductors to be fabricated routinely, as is the case for YBCO. This will enable the field trapping and current-carrying characteristics of these materials to be explored in more detail than has been possible to date. (rapid communication)

  2. Muon spin depolarization in Gd- and EuBa1Cu3O/sub x/

    International Nuclear Information System (INIS)

    Cooke, D.W.; Hutson, R.L.; Kwok, R.S.

    1988-01-01

    Positive muon spin rotation (μSR) measurements on Gd- and EuBa 2 Cu 3 O/sub x/ (x ∼ 7) have been conducted in the temperature interval 4-300K. For each sample, muons stop both at grain boundaries and within the superconducting grains. Measured magnetic field penetration depths are 1550 and 1900/angstrom/ for two specimens of GdBa 2 Cu 3 O/sub x/, and 1350/angstrom/ for EuBa 2 Cu 3 O/sub x/. 2 refs., 5 figs

  3. Formation of layered microstructure in the Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O superconductors

    International Nuclear Information System (INIS)

    Jin, S.; Kammlott, G.W.; Tiefel, T.H.; Chen, S.K.

    1992-01-01

    The layered grain microstructure is essential for overcoming the weak link problem and ensuring high transport critical currents in the cuprate superconductors. In this paper we discuss the processing and the mechanisms for layer information in Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O. In melt-processed Y-Ba-Cu-O, sympathetic nucleation on previously nucleated YBa 2 Cu 3 O 7-δ plates during solidification appears to be dominant mechanism for the formation of parallel plate-shaped grains. In the Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O ribbons, the interface reaction between the superconductor layer and the silvers substrate seems to be the main mechanism for the c-axis texturing of the layered grains. The drastically different critical current behavior in the c-axis textured Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O ribbons is discussed in terms of possible differences in the nature of the twist and tilt grain boundaries. (orig.)

  4. Effect of silver doping on infrared reflectance and Tc of superconducting GdBa2Cu(1 - x)3Ag3xO7

    International Nuclear Information System (INIS)

    Memon, A.; Khan, M.N.; Al-Dallal, S.; Tanner, D.B.; Porter, C.D.

    1990-01-01

    This paper reports on infrared reflectance of GdBa 2 Cu(1 - x) 3 Ag 3x O 7 ceramic superconductor with the composition of x = 0.025 and 0.05 performed in the frequency range of 100--5000 cm -1 . All the infrared active phonon modes allowed by the selection rules were observed in the reflection spectra of these compounds. The optical conductivity as calculated from K--K analysis further confirms the existence of these optical phonons. Besides the increase of the reflectivity in the silver doped samples, an extra phonon mode is observed, which is normally not seen at room temperature reflectance of GdBa 2 Cu 3 O 7 compounds. The four probe resistivity measurement show zero resistance at 88 K for x = 0, and 78 K for x = 0.025 in GdBa 2 Cu(1 - x) 3 Ag 3x O 7 compound

  5. Melt-processed LRE-Ba-Cu-O superconductors and prospects for their applications

    International Nuclear Information System (INIS)

    Yoo, S.I.; Fujimoto, H.; Sakai, N.; Murakami, M.

    1997-01-01

    We have recently found that control of the oxygen partial pressure (PO 2 ) during melt processing, named the oxygen-controlled melt-growth (OCMG) process, is critical for obtaining a high superconducting transition temperature (T c ) in the light rare earth (LRE)-Ba-Cu-O (LREBCO) superconductors particularly for Nd, Sm and Eu. Further, compared to a good melt-processed Y-Ba-Cu-O (YBCO) bulk superconductor, LREBCO bulks exhibit larger critical current density (J c ) in high magnetic field and a much improved irreversibility field (H irr ) at 77 K, implying that more effective flux pinning can be realized in a commercially feasible way. In this paper, properties and characteristic flux pinning of OCMG-processed LREBCO (LRE: Nd,Sm,Eu) superconductors are described on the basis of our study during the last several years. We also present the prospects for bulk-type applications, such as the magnetic bearings, flywheels and magnetically levitated (MAGLEV) trains. (orig.)

  6. Temperature dependence of the mechanical properties of melt-processed Dy-Ba-Cu-O bulk superconductors evaluated by three point bending tests

    International Nuclear Information System (INIS)

    Katagiri, K; Nyilas, A; Sato, T; Hatakeyama, Y; Hokari, T; Teshima, H; Iwamoto, A; Mito, T

    2006-01-01

    Dy-Ba-Cu-O bulk superconductor has an excellent capability of trapping magnetic flux and lower heat conductivity at cryogenic temperatures as compared with Y-Ba-Cu-O bulk superconductor. The Young's modulus and the bending strength in the range from room temperature to 7 K were measured by the three-point bending tests using specimens cut from a melt-processed Dy-Ba-Cu-O bulk superconductor. They were tested in a helium gas flow type cryostat at Forschungszentrum Karlsruhe and in a liquid nitrogen bath at Iwate University. The Young's modulus was calculated by either the slope of stress-strain curve or that of the load-deflection curve of the specimen. Although the bending strength measured in the two institutes coincided well, there was a significant discrepancy in the Young's modulus. The Young's modulus and bending strength increased with decrease of temperature down to 7 K. The amount of increase in the Young's modulus and the bending strength were about 32% and 36% of those at room temperature, respectively. The scatter of data for each run was significant and did not depend on temperature. The temperature dependence of the Young's modulus coincided with that in Y-Ba-Cu-O obtained by ultrasonic velocity. The temperature dependence of the Young's modulus and the bending strength was discussed from the view point of interatomic distance of the bulk crystal

  7. Electrical and structural properties of GdBa2Cu3-xVxO7-x

    International Nuclear Information System (INIS)

    Javanmard, H.; Bazargan, S.; Akhavan, M.

    2007-01-01

    Full text: It is well known that the characteristics of the CuO 2 planes are essential for understanding the unconventional superconductivity and the anomalous transport behavior of the normal state in cuprate superconductors. Continuous efforts have been devoted to the study of effects of substitution for Cu, which are of great importance for understanding the role of Cu in high-Tc superconductivity. The bulk samples of GdBa 2 Cu 3-x V x O 7-x with 0.0 4+ in the compound, and because of the high tendency of the V 4+ for achieving the octahedral structure, it appears that vanadium enters the chains, which accounts for the observed changes in the crystal structure and superconducting properties. (authors)

  8. Structural and Transition Temperature of HgPbxBa2Ca2Cu3O8+δ Superconductor

    International Nuclear Information System (INIS)

    Hermiz, G.Y.; Abbass, M.M.

    2005-01-01

    Solid state reaction technique (SSR) was used to prepare high-T c phase in HgPb x Ba 2 Ca 2 Cu 3 O 8+δ superconductors. The effect of additional Pb to HgBa 2 Ca 2 Cu 3 O 8+δ was investigated. It has been found that the maximum transition temperature T c =133K is at x=0.1.X-ray diffraction showed a tetragonal structure with an average value of e=15.816 A . The average value of the valence of copper (v) is equal to 2.025. There is an increasing of density with the enhancement of the concentration of Pb 2

  9. Positron annihilation studies on high temperature superconductors

    International Nuclear Information System (INIS)

    Sundar, C.S.; Bharathi, A.

    1991-01-01

    The results of positron annihilation measurements as a function of temperature, across Tc, in a variety of high temperature superconductors such as Y-Ba-Cu-O (Y1237), Y-Ba-Cu-O (Y1248), Bi-Sr-Ca-Cu-O, Tl-Ba-Ca-Cu-O, Ba-K-Bi-O and Nd-Ce-Cu-O are presented. It is shown that the variation of annihilation parameters in the superconducting state is correlated with the diposition of the positron density distribution with respect to the superconducting CuO planes. An increase in positron lifetime is observed below Tc when the positrons probe the CuO planes whereas a decrease in lifetime is observed when the positron density overlaps predominantly with the apical oxygen atom. With this correlation, the different temperature variation of annihilation parameters, seen in the various high temperature superconductors, is understood in terms of a local charge transfer from the planar oxygen atom to the apical oxygen atom. The significance of these results in the context of various theoretical models of high temperature superconductivity is discussed. In addition, the application of positron annihilation spectroscopy to the study of oxygen defects in the Y-Ba-Cu-O, Bi-Sr-Ca-Cu-O and Nd-Ce-Cu-O is presented. (author). 53 refs., 17 figs., 2 tabs

  10. Muon spin depolarization in Gd- and EuBa2Cu3Ox

    International Nuclear Information System (INIS)

    Cooke, D.W.; Hutson, R.L.; Kwok, R.S.; Maez, M.; Rempp, H.; Schillaci, M.E.; Smith, J.L.; Willis, J.O.; Lichti, R.L.; Chan, K.C.; Boekema, C.; Weathersby, S.; Oostens, J.

    1989-01-01

    Positive muon spin rotation (μSR) measurements on Gd- and EuBa 2 Cu 3 O x (x ∼ 7) have been conducted in the temperature interval 4 - 300 K. For each sample, muons stop both at grain boundaries and within the superconducting grains. Measured magnetic field penetration depths are 1550 and 1900 Angstrom for two specimens of GdBa 2 Cu 3 O x , and 1350 Angstrom for EuBa 2 Cu 3 O x

  11. Stoichiometric analysis of Y-Ba-Cu-O superconductors using deuterons

    International Nuclear Information System (INIS)

    Tang, S.M.; Ong, T.H.; Tan, M.G.; Loh, K.K.; Sow, C.H.; Yuan, B.; Orlic, I.

    1993-01-01

    In principle, deuteron irradiation can be used for a complete stoichiometric analysis of Y-Ba-Cu-O superconductors. The contents of all the four chemical constituents can be determined by simultaneous detection of the 0.871 MeV prompt gamma rays from the 16 O(d, pγ) 17 O * reaction and of the characteristic X-rays produced by DIXE (deuteron induced X-ray emission). In this paper we present the approach taken and the results obtained in exploring the applicability of this technique for accurate quantitative determinations of the chemical constituents of bulk Y-Ba-Cu-O superconductors. (orig.)

  12. Experimental studies of effect of high current pulse electron and carbon ion beams on high temperature Y-Ba-Cu-O, Bi-Ca-Sr-Cu-O superconductors

    International Nuclear Information System (INIS)

    Korenev, S.A.; Sikolenko, V.V.; Chernakova, A.

    1989-01-01

    This work shows the results of the experiment on the effect of high current electron and carbon ion pulse beams irradiation on High-T c superconductors Y-Ba-Cu-O and Bi-Ca-Cu-O in vacuum (P∼5x10 -5 torr). The parameters of electron beam used in the experiment were: E∼100-300 keV, j e ∼10-1000 A/cm 2 , τ) p ∼300ns. The parameters of carbon ions used in the experiment were: E∼100-300keV j i ∼1-60A/cm, τ p ∼300ns. Experiments had shown the threshold electron beam power density for surface melting in adiabatic heat condition for Y-Ba-Cu-O ceramics up to P 0 >or approx. 10 7 W/cm 2 , and for Bi-Ca-Sr-Cu-O ceramics up to P 0 ∼4x10 6 W/cm 2 . Increasing of critical current in ∼2 times was observed in samples with a melting surface layer. The integral resistance of Y-Ba-Cu-O and Bi-Ca-Sr-Cu-O decreased in ∼2-2.5 times for electron beam irradiated samples and in ∼1.25-1.8 times for ion irradiated samples. Amorphization did not take place and stoichiometry remained after such irradiation. 6 refs.; 2 figs.; 1 tab

  13. Substitutions in cation Nd/Ba subsystem in thin films of high-temperature superconductor NdBa2Cu3Oy

    International Nuclear Information System (INIS)

    Mozhaev, P.B.; Komissinskij, F.V.; Ivanov, Z.G.; Ovsyannikov, G.A.

    2000-01-01

    Thin films of the Nd 1+x Ba 2-x Cu 3 O y (NBCO) high-temperature superconductor with various neodymium and barium ratio are obtained through the method of combined laser spraying of targets with different elements composition. The films with neodymium excess (x >0) had low density of particles on the surface and roughness, however the critical temperature decreased with growth of x. The films with barium excess (x z particles. The NbCO structure and superconducting properties demonstrate strong dependence on the conditions of the films saturation with oxygen [ru

  14. Effect of mixing RE elements (Nd, Sm, Gd, Eu, Y, Yb) on the RE2BaCuO5/Nd4-2xBa2+2xCu2-xO10-2x phases in RE cuprate high-Tc superconductors

    International Nuclear Information System (INIS)

    Langhorn, J.B.; Black, M.A.; McGinn, P.J.

    1999-01-01

    The phases RE 2 BaCuO 5 /RE 4 Ba 2 Cu 2 O 10 phases (where RE is a mixture of Nd, Sm, Gd, Eu, Y and Yb) have been synthesized in an oxygen atmosphere and subsequently characterized. The mixing of RE elements which inherently form the RE 2 BaCuO 5 phase through the peritectic decomposition of REBa 2 Cu 3 O 7-x (RE123) (i.e. Sm, Gd, Eu, Y, Yb), was observed to give homogeneous mixing of the elements in the 211 phase. In contrast it was found that on mixing Nd with other RE elements a mixture of the Nd 4-2x Ba 2+2x Cu 2-x O 10-2x (Nd422) and RE 2 BaCuO 5 (RE211) phases resulted. It was also observed that on mixing Nd with other REs a finite amount of the RE is substituted into the Nd422 phase and Nd into the RE211. (author)

  15. Materials process and applications of single grain (RE)-Ba-Cu-O bulk high-temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Li Beizhan; Zhou Difan; Xu Kun; Hara, Shogo; Tsuzuki, Keita; Miki, Motohiro; Felder, Brice; Deng Zigang [Laboratory of Applied Physics, Department of Marine Electronics and Mechanical Engineering, Tokyo University of Marine Science and Technology (TUMSAT), 2-1-6, Etchu-jima, Koto-ku, Tokyo 135-8533 (Japan); Izumi, Mitsuru, E-mail: izumi@kaiyodai.ac.jp [Laboratory of Applied Physics, Department of Marine Electronics and Mechanical Engineering, Tokyo University of Marine Science and Technology (TUMSAT), 2-1-6, Etchu-jima, Koto-ku, Tokyo 135-8533 (Japan)

    2012-11-20

    This paper reviews recent advances in the melt process of (RE)-Ba-Cu-O [(RE)BCO, where RE represents a rare earth element] single grain high-temperature superconductors (HTSs), bulks and its applications. The efforts on the improvement of the magnetic flux pinning with employing the top-seeded melt-growth process technique and using a seeded infiltration and growth process are discussed. Which including various chemical doping strategies and controlled pushing effect based on the peritectic reaction of (RE)BCO. The typical experiment results, such as the largest single domain bulk, the clear TEM observations and the significant critical current density, are summarized together with the magnetization techniques. Finally, we highlight the recent prominent progress of HTS bulk applications, including Maglev, flywheel, power device, magnetic drug delivery system and magnetic resonance devices.

  16. Materials process and applications of single grain (RE)-Ba-Cu-O bulk high-temperature superconductors

    Science.gov (United States)

    Li, Beizhan; Zhou, Difan; Xu, Kun; Hara, Shogo; Tsuzuki, Keita; Miki, Motohiro; Felder, Brice; Deng, Zigang; Izumi, Mitsuru

    2012-11-01

    This paper reviews recent advances in the melt process of (RE)-Ba-Cu-O [(RE)BCO, where RE represents a rare earth element] single grain high-temperature superconductors (HTSs), bulks and its applications. The efforts on the improvement of the magnetic flux pinning with employing the top-seeded melt-growth process technique and using a seeded infiltration and growth process are discussed. Which including various chemical doping strategies and controlled pushing effect based on the peritectic reaction of (RE)BCO. The typical experiment results, such as the largest single domain bulk, the clear TEM observations and the significant critical current density, are summarized together with the magnetization techniques. Finally, we highlight the recent prominent progress of HTS bulk applications, including Maglev, flywheel, power device, magnetic drug delivery system and magnetic resonance devices.

  17. Chemical stability of high-temperature superconductors

    Science.gov (United States)

    Bansal, Narottam P.

    1992-01-01

    A review of the available studies on the chemical stability of the high temperature superconductors (HTS) in various environments was made. The La(1.8)Ba(0.2)CuO4 HTS is unstable in the presence of H2O, CO2, and CO. The YBa2Cu3O(7-x) superconductor is highly susceptible to degradation in different environments, especially water. The La(2-x)Ba(x)CuO4 and Bi-Sr-Ca-Cu-O HTS are relatively less reactive than the YBa2Cu3O(7-x). Processing of YBa2Cu3O(7-x) HTS in purified oxygen, rather than in air, using high purity noncarbon containing starting materials is recommended. Exposure of this HTS to the ambient atmosphere should also be avoided at all stages during processing and storage. Devices and components made out of these oxide superconductors would have to be protected with an impermeable coating of a polymer, glass, or metal to avoid deterioration during use.

  18. Stabilization of high-temperature supeconductor Y1Ba2Cu3O7-δ surface

    International Nuclear Information System (INIS)

    Korenev, S.A.; Valentovich, D.; Lushchikov, V.I.

    1988-01-01

    A technique is suggested for stabilization of a high-temperature superconductor Y 1 Ba 2 Cu 3 O 7-δ surface by means of a high-current pulsed electron beam (J=12.5-65 A/cm 2 , E=70-200 keV, t=300 ns, P=0.001 Pa). The quality of the remelted surface film is characterized and first experimental results are discussed. It is shown that within 50 days after the electron beam processing, no dielectric film was developed at the superconductor surface and superconductor characteristics did not change

  19. Magnetization fluctuation analysis and superconducting parameters of La0.5RE0.5BaCaCu3O7-δ(RE=Y, Sm, Gd, Dy, Ho, Yb) superconductor

    International Nuclear Information System (INIS)

    Parra Vargas, C.A.; Pimentel, J.L.; Pureur, P.; Landinez Tellez, D.A.; Roa-Rojas, J.

    2009-01-01

    In this work we report the analysis of magnetization experimental data of the La 0.5 RE 0.5 BaCaCu 3 O 7-δ (RE=Y, Sm, Gd, Dy, Ho, Yb) superconducting system. The data are analyzed in terms of thermal fluctuations on the magnetization excess ΔM(T) for different values of temperature in each one of the samples. We describe a procedure for extracting the penetration depth λ ab (∼1571A) and the coherence length ξ ab (∼1.52A) parameters from the magnetization, as a function of the applied magnetic field. This procedure was performed for polycrystalline samples of La 0.5 RE 0.5 BaCaCu 3 O 7-δ by using the theory of Bulaevskii, Ledvij and Kogan, which analyzes the vortex fluctuation in superconducting materials within the Lawrence-Doniach framework. These data allowed to determine the characteristic temperature value T * (73, 58, 48, 57, 56, 71 K, for RE=Y, Sm, Gd, Dy, Ho, Yb, respectively) in the magnetization curves for several magnetic fields. We calculated the data of magnetization excess from the curves of magnetization as a function of logarithm of applied field. We notice that the values for these superconducting parameters are in agreement with the reports for high temperature superconductors. The obtained value of superconducting volumetric fraction is compared with that obtained through the measure of the Meissner effect.

  20. Point-contact electron tunneling into the high-Tc superconductor Y-Ba-Cu-O

    Science.gov (United States)

    Kirk, M. D.; Smith, D. P. E.; Mitzi, D. B.; Sun, J. Z.; Webb, D. J.

    1987-06-01

    Results are reported from a study of electron tunneling into bulk samples of the new high-Tc superconductor Y-Ba-Cu-O using point-contact tunneling. Based on a superconductive tunneling interpretation, the results show exceptionally large energy gaps in these materials (roughly 2Delta = 100 MeV), implying 2Delta/kBTc = about 13. Similar values were found for La-Sr-Cu-O. The structure in the I-V curves is also similar to that seen in La-Sr-Cu-O. From the asymmetries observed in the I-V characteristics, it is inferred that the natural tunneling barrier on this material is of the Schottky type.

  1. Superconducting transition temperature in the Y(1-x)M(x)Ba2Cu3O(y) system

    Science.gov (United States)

    Suzuki, Takeyuki; Yamazaki, Tsutomu; Sekine, Ryuuta; Koukitsu, Akinori; Seki, Hisashi

    1989-04-01

    Experimental results are presented for the inclusion of compositional additives, M, to the sintered high-temperature superconductor Y(1-x)M(x)Ba2Cu3O(y); M can be the oxides of Mg, Ce, Gd, Yb, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Zn, B, Al, Ga, In, Si, Ge, Sn, Pb, Sb, Bi, and Te, as well as Li, Na, K, Ca, Sr, and La carbonates. Temperature dependence of the electrical resistance was measured down to about 80 K. Attention is given to the influence of ionic radius and the valence of the M species.

  2. The study on a new superconductor (oxide Ba-Y-Cu) with high critical temperature Tc by positron annihilation

    International Nuclear Information System (INIS)

    Zhang Caigu; Yu Zhuxing; Wang Zhu; Huang Zhe; Zhou Jun

    1987-01-01

    The study on a new superconductor oxide Ba-Y-Cu with high critical temperature Tc is described. The experimental results show that positron lifetime reducing reflects variable curve of resistance with temperature. A peak of positron lifetime is appeared at critical temperature

  3. Hot spot in GdBa2Cu3O7-δ-based composite ceramics rods and their applications for oxygen sensors

    International Nuclear Information System (INIS)

    Okamoto, T; Takata, M

    2011-01-01

    A hot spot, which is a local area glowing orange, appears in a LnBa 2 Cu 3 O 7-δ (Ln: rare earth element) ceramic rod when a voltage exceeding a certain value is applied to the rod at room temperature. After the appearance of the hot spot, the current changes according to the oxygen partial pressure in ambient atmosphere, which acts as an oxygen sensor without the need for any heating system. The GdBa 2 Cu 3 O 7-δ rod tended to be melted and broken by a sustained presence of the hot spot in a high oxygen partial pressure Po 2 (∼100 kPa). The composite rod containing high melting point materials, such as BaAl 2 O 4 , BaZrO 3 and Gd 2 BaCuO 5 , showed a remarkable high durability in O 2 atmosphere. In a low Po 2 ( 2 Cu3O 7-δ rod decreases to almost zero and the hot spot disappeared, resulting in an insensitive rod to oxygen. The composite rod containing CuO detected oxygen even in Po 2 < 0.002 kPa.

  4. A low-cost batch process for high-performance melt-textured GdBaCuO pellets

    Czech Academy of Sciences Publication Activity Database

    Muralidhar, M.; Tomita, M.; Suzuki, K.; Jirsa, Miloš; Fukumoto, .Y.; Ishihara, A.

    2010-01-01

    Roč. 23, č. 4 (2010), 045033/1-045033/7 ISSN 0953-2048 Institutional research plan: CEZ:AV0Z10100520 Keywords : superconducting magnet * GdBaCuO * batch process * high-Tc bulk Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.402, year: 2010

  5. State-of-the-art flux pinning in YBa2Cu3O7-δ by the creation of highly linear, segmented nanorods of Ba2(Y /Gd)(Nb/Ta)O6 together with nanoparticles of (Y /Gd)2O3 and (Y /Gd)Ba2Cu4O8

    International Nuclear Information System (INIS)

    Ercolano, G; Bianchetti, M; Wimbush, S C; Harrington, S A; MacManus-Driscoll, J L; Wang, H; Lee, J H

    2011-01-01

    Self-assembled, segmented nanorods of c-axis-aligned Ba 2 (Y /Gd)(Nb/Ta)O 6 as well as randomly distributed nanoparticles of (Y /Gd) 2 O 3 and (Y /Gd)Ba 2 Cu 4 O 8 were grown into YBa 2 Cu 3 O 7-δ (YBCO) thin films by pulsed-laser deposition. The complex pinning landscape proves to be extremely effective, particularly at higher fields where the segmented vortices yield a plateau in critical current density (J c ) with field angle around 60 0 . In 0.3 μm thick films, the J c values are higher than 1 MA cm -2 at 2.5 T (H||c axis). Owing to the combined interactions of the vortices with the different pinning centres, interesting new features are observed at high fields in the angular dependence of J c .

  6. Effect of BSO addition on Cu-O bond of GdBa{sub 2}Cu{sub 3}O{sub 7-x} films with varying thickness probed by extended x-ray absorption fine structure

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, H. K.; Lee, J. K.; Yang, D. S.; Kang, B. [Chungbuk National University, Cheongju (Korea, Republic of); Kang, W. N. [Dept. of Physics, Sungkyunkwan University, Suwon (Korea, Republic of)

    2016-12-15

    We investigated the relation between the Cu-O bond length and the superconducting properties of BaSnO{sub 3} (BSO)-added GdBa{sub 2}Cu{sub 3}O{sub 7-x} (GdBCO) thin films by using extended x-ray absorption fine structure (EXAFS) spectroscopy. 4 wt.% BaSnO{sub 3} (BSO) added GdBa{sub 2}Cu{sub 3}O{sub 7-x} (GdBCO) thin films with varying thickness from 0.2 μm to 1.0 μm were fabricated by using pulsed laser deposition (PLD) method. The transition temperature (T{sub c}) and the residual resistance ratio (RRR) of the GdBCO films increased with increasing thickness up to 0.8 μm, where the crystalline BSO has the highest peak intensity, and then decreased. This uncommon behaviors of T{sub c} and RRR are likely to be created by the addition of BSO, which may change the ordering of GdBCO atomic bonds. Analysis from the Cu K-edge EXAFS spectroscopy showed an interesting thickness dependence of ordering behavior of BSO-added GdBCO films. It is noticeable that the ordering of Cu-O bond and the transition temperature are found to show opposite behaviors in the thickness dependence. Based on these results, the growth of BSO seemingly have evident effect on the alteration of the local structure of GdBCO film.

  7. Development of Y-Ba-Cu-O Superconductors for Magnetic Bearings

    Science.gov (United States)

    Selvamanickam, V.; Pfaffenbach, K.; Sokolowski, R. S.; Zhang, Y.; Salama, K.

    1996-01-01

    The material requirements, material manufacturing and magnetic properties that are relevant to fabrication of High Temperature Superconductor (HTS) magnetic bearings have been discussed. It is found that the seeded-melt-texturing method can be used to fabricate the single domain material that is required to achieve the best magnetic properties. Trapped-field mapping has been used as a non-destructive tool to determine the single-domain nature of the HTS material and quantity of the HTS disks. Both the trapped field and the levitation force of the Y-Ba-Cu-O disks are found to be strongly sensitive to the oxygen content.

  8. Flux motion in Y-Ba-Cu-O bulk superconductors during pulse field magnetization

    International Nuclear Information System (INIS)

    Yoshizawa, K; Nariki, S; Sakai, N; Murakami, M; Hirabayasi, I; Takizawa, T

    2004-01-01

    We have studied the relationship between the magnetization and temperature change in Y-Ba-Cu-O bulk superconductor during pulse field magnetization (PFM). The flux motion was monitored using both Hall sensors and pick-up coils that are placed on a surface of a Y-Ba-Cu-O disc having dimensions of 15 mm in diameter and 0.95 mm in thickness. The peak value of the field was varied from 0.2 to 0.8 T. The effect of the static bias field was also studied in the range of 0-3 T. The temperature of the sample surface was measured using a resistance temperature sensor. The temperature increased with the magnitude of the applied pulsed magnetic field, and the amount of temperature rise decreased with increasing static bias field

  9. Smooth surfaces in very thin GdBa2Cu3O7−δ films for application in superconducting tunnel junctions

    International Nuclear Information System (INIS)

    Navarro, H.; Sirena, M.; Kim, Jeehoon; Haberkorn, N.

    2015-01-01

    Highlights: • A detailed study of the morphological properties of GdBa 2 Cu 3 O 7−δ thin films was realized. • The inclusion of a very thin SrTiO 3 buffer layer modifies the surface of the SrTiO 3 substrates. • The inclusion of the buffer layer suppress the three dimensional nucleation in the GdBa 2 Cu 3 O 7−δ film. • GdBa 2 Cu 3 O 7−δ films with large areas free of topological defects and T c close to liquid nitrogen can be obtained. - Abstract: This paper provides a systematic analysis of the morphology and the superconducting critical temperature obtained in very thin GdBa 2 Cu 3 O 7−δ films grown on (0 0 1) SrTiO 3 substrates by DC sputtering. We find that the use of a very thin SrTiO 3 buffer layer (≈2 nm) modify the nucleation of GdBa 2 Cu 3 O 7−δ on the surface of the substrate reducing the formation of 3 dimensional clusters. Our results demonstrate that 16 nm thick GdBa 2 Cu 3 O 7−δ films with an average root-mean-square (RMS) smaller than 1 nm and large surface areas (up 10 μm 2 ) free of 3 dimensional topological defects can be obtained. In films thinner than 24 nm the onset (zero resistance) of superconducting transition of the films is reduced, being close to liquid nitrogen. This fact can be associated with stress reducing the orthorhombicity and slightly drop in oxygen stoichiometry

  10. NMR/NQR study of the superconductor Y2Ba4Cu7O15

    International Nuclear Information System (INIS)

    Stern, R.

    1995-01-01

    This dissertation concentrates on several important aspects of the high temperature superconductivity research. Nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) studies in Y-Ba-O compounds contribute information regarding various aspects, ranging from the direct observation of strong coupling between the adjacent planes in the double plane to conclusions concerning the spatial symmetry of paring state in these cuprates. We report the first results in the 93 K superconductor Y 2 Ba 4 Cu 7 O 15 . This compound turns out to be a structure containing differently doped CuO 2 planes. The planes in the 1-2-3(1-2-4) block are only slightly lower (higher) doped than those in the corresponding parent compounds YBa 2 Cu 3 O 7 and YBa 2 Cu 4 O 8 . The results obtained from measurements on oxygen depleted Y 2 Ba 4 Cu 7 O 15-x show two new features which could explain the dissimilar variation of T c with oxygen content compared to YBa 2 Cu 3 O 7-x : i) the double chains donate charge carriers to the planes and ii) the chain fragments which survive when emptying single chains are longer than in YBa 2 Cu 3 O 7-x . The pressure induced charge transfer from chain to plane in each block of Y 2 Ba 4 Cu 7 O 15 is the same as in the corresponding parent compound. We explore the strong coupling between nonequivalent planes in this compound using the three main NMR/NQR quantities, K spin , 1/T 1 ; and T 2G,ind , and estimate its approximate strength directly from spin-echo double resonance (SEDOR) experiments. We obtain for the ratio of the effective inter- and intraplane exchange-coupling constants the value of 0.3 just above T c . This ratio decreases with increasing temperature. (author) figs., tabs., refs

  11. Parasitic phase formation in the La Ba2 Cu3 O7-x superconductor

    International Nuclear Information System (INIS)

    Baltra, T.; Fuenzalida, V.M.; Grahmann, C.R.

    1996-01-01

    The parasitic phase formation during the thermal processing of the H Tc La Ba 2 Cu 3 O 7-x superconductor, particularly the Ba Cu O 2 , is studied. The formation of the stable parasitic phase depends on the temperature of the initial treatments and on the heating rate during the sintering process. The superconducting highest purity material is obtained with treatment at 900 deg C and lowest heating rate. The temperature during the final annealing in oxygen of the sample did also affect the transport properties. Samples with the lowest resistivity in the normal state were produced by annealing in oxygen at 300 deg C. The largest orthorhombic distortion was obtained at 325 deg C. (author)

  12. Influence of the Gd.sub.2./sub.BaCuO.sub.5./sub. fine particles on thermoelectric power of melt-textured (Nd-Sm-Gd) Ba.sub.2./sub.Cu.sub.3./sub.O.sub.7 -.delta../sub.

    Czech Academy of Sciences Publication Activity Database

    Okram, G. A.; Muralidhar, M.; Jirsa, Miloš; Murakami, M.

    2004-01-01

    Roč. 402, - (2004), s. 94-97 ISSN 0921-4534 Institutional research plan: CEZ:AV0Z1010914 Keywords : melt-textured materials * thermoelectric power * (Nd,Sm,Gd)Ba 2 Cu 3 O y * Gd 2 BaCuO 5 Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.072, year: 2004

  13. Enhanced critical currents in (Gd,Y)Ba2Cu3Ox superconducting tapes with high levels of Zr addition

    International Nuclear Information System (INIS)

    Selvamanickam, V; Shi, T; Liu, Y; Khatri, N D; Liu, J; Yao, Y; Galstyan, E; Majkic, G; Chen, Y; Xiong, X; Lei, C; Soloveichik, S

    2013-01-01

    The critical current and structural properties of (Gd,Y)BaCuO tapes made by metal organic chemical vapor deposition (MOCVD) with Zr addition levels up to 30 at.% have been investigated. The reduction in critical current beyond the previously optimized Zr addition level of 7.5 at.% was found to be due to structural deterioration of the (Gd,Y)Ba 2 Cu 3 O x film. By a modified MOCVD process, enhanced critical current densities have been achieved with high levels of Zr addition, including 3.83 MA cm −2 in 15 at.% Zr-added 1.1 μm thick film at 77 K in zero magnetic field. Critical currents as high as 1072 A/12 mm have been reached in (Gd,Y)BaCuO tapes with 15 at.% Zr addition at 30 K in a field of 3 T applied perpendicular to the tape, corresponding to a pinning force value of 268 GN m −3 . The enhanced critical currents achievable with a high density of nanoscale defects by employing high levels of second-phase additions enable the performance targets needed for the use of HTS tapes in coil applications involving high magnetic fields at temperatures below 50 K to be met. (paper)

  14. First-principles calculation of the transition temperature Tc for HgBa2CuO4+δ high-temperature superconductors via dipolon theory

    International Nuclear Information System (INIS)

    Downs, D.; Sharma, R.R.

    1995-01-01

    First numerical evaluations of T c for oxygenated and argon-reduced single-layered HgBa 2 CuO 4+δ superconductors have been presented. Our calculations are based on the dipolon theory and are found to provide an explanation for the occurrence of superconductivity in single-layered high-T c superconductors. Relevant expressions useful for the evaluation of T c have been given. Since the polarizabilities of the ions are not known exactly for the present systems we have performed calculations making use of Pauling's as well as Tessman, Kahn, and Shockley's polarizabilities in order to estimate the uncertainties in the calculated values of T c associated with uncertainties in the polarizabilities. The effective charges on the ions required for the evaluation of dipoles and dipolon frequencies have been obtained by means of the bond-valence sums. Without fitting with any parameters, our calculations yield T c values equal to 80±21 K for the oxygenated and 50±27 K for the argon-reduced HgBa 2 CuO 4+δ superconductors, in agreement with the corresponding experimental values 95 and 59 K. The uncertainties in the calculated values of T c arise because of the uncertainties in various physical parameters (including polarizabilities) used and due to errors involved in the calculations. The present results are consistent with the observed electronic Raman-scattering intensities which show anomalously broad peaks extended up to several electron volts in cuprate high-T c superconductors. Our calculated dipolon density of states predict four optical absorption peaks at about 77 cm -1 , 195 cm -1 , 1.6 eV, and 2.5 eV

  15. Synthesis and studies of Y-Ba-Cu-O high temperature superconductor prepared by sol-gel method

    International Nuclear Information System (INIS)

    Grigoryan, S.G.; Manukyan, A.L.; Hayrapetyan, A.G.; Arzumanyan, A.M.; Rashidyan, L.H.; Mkrtichyan, N.Y.; Mkrtchyan, A.A.; Kurginyan, K.A.; Trozyan, A.H.; Vardanyan, R.S.

    2004-01-01

    The method of preparation of Y-Ba-Cu-O high temperature superconducting materials by sol-gel processing technique both for powders and thin films are described. All these methods are based on using yttrium alkoxides as precursors, which are not ready available reagents, besides the majority of these methods use copper alkoxides, which show low solubility in organic solvents, moreover they are very sensitive to hydrolysis in air. The new method of preparation of Y-Ba-Cu-O ceramic materials by sol-gel processing technique based on new and convenient precursors stable in air, having high compatibility with each other is offered. Basic scientific and technological issues related to the synthesis of bulk materials, their structure and electrical conductivity are discussed

  16. Dielectric properties of (CuO,CaO2, and BaO)y/CuTl-1223 composites

    International Nuclear Information System (INIS)

    Mumtaz, M.; Kamran, M.; Nadeem, K.; Jabbar, Abdul; Khan, Nawazish A.; Saleem, Abida; Hussain, S.Tajammul; Kamran, M.

    2013-01-01

    We synthesized (CuO, CaO 2 , and BaO) y /Cu 0.5 Tl 0.5 Ba 2 Ca 2 Cu 3 O 10-δ (y = 0, 5%, 10%, 15%) composites by solid-state reaction and characterized by x-ray diffraction, scanning electron microscopy, dc-resistivity, and Fourier transform infrared spectroscopy. Frequency and temperature dependent dielectric properties such as real and imaginary part of dielectric constant, dielectric loss, and ac-conductivity of these composites are studied by capacitance and conductance measurement as a function of frequency (10 kHz to 10 MHz) and temperature (78 to 300 K). The x-ray diffraction analysis reveals that the characteristic behavior of Cu 0.5 Tl 0.5 Ba 2 Ca 2 Cu 3 O 10-δ superconductor phase and its structure is nearly undisturbed by doping of nanoparticles. The scanning electron microscopy images show the improvement in the intergranular links among the superconducting grains with increasing nanoparticles concentration. Microcracks are healed up with the inclusion of these nanoparticles and superconducting volume fraction is also increased. The dielectric properties of these composites strongly depend upon the frequency and temperature. The zero resistivity critical temperature and dielectric properties show opposite trend with the addition of nanoparticles in Cu 0.5 Tl 0.5 Ba 2 Ca 2 Cu 3 O 10-δ superconductor matrix.

  17. High performance GdBa{sub 2}Cu{sub 3}O{sub 7-z} film preparation by non-fluorine chemical solution deposition approach

    Energy Technology Data Exchange (ETDEWEB)

    Wang, W.T.; Pu, M.H.; Wang, W.W. [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Zhang, H. [Department of Physics, Peking University, Beijing 100871 (China); Cheng, C.H. [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China)] [Superconductivity Research Group, School of Materials Science and Engineering, University of New South Wale, Sydney, 2052 NSW (Australia); Zhao, Y., E-mail: yzhao@swjtu.edu.cn [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China)] [Superconductivity Research Group, School of Materials Science and Engineering, University of New South Wale, Sydney, 2052 NSW (Australia)

    2011-11-15

    Biaxially textured GdBa{sub 2}Cu{sub 3}O{sub 7}-z films with Tc above 93 K have been prepared on (0 0 l) by non-fluorine CSD approach. Nanoparticles with homogeneous distribution are introduced into the GdBCO films as effective pinning centers. A high Jc (77 K, 0 T) of 2.28 MA/cm{sup 2} with slow decreasing Jc-B behavior is observed in the films. Biaxially textured GdBa{sub 2}Cu{sub 3}O{sub 7-z} (GdBCO) films with T{sub c} above 93 K have been prepared on (0 0 l) LaAlO{sub 3} substrate by self-developed non-fluorine polymer-assisted chemical solution deposition (PA-CSD) approach. The GdBCO films show smooth and crack-free morphology. Many nanoscale particles with homogeneous distribution are observed in the GdBCO films, which have not been observed yet in the YBa{sub 2}Cu{sub 3}O{sub 7-z} (YBCO) films prepared by the same processing technique. Besides a high J{sub c} (77 K, 0 T) of 2.28 MA/cm{sup 2}, the optimized GdBCO films show a better J{sub c}-B behavior and an improved high-field J{sub c}, compared to the YBCO films.

  18. Flux pinning enhancement by Y2BaCuO5 inclusions in melt processed YBaCuO superconductors

    International Nuclear Information System (INIS)

    Murakami, M.

    1991-01-01

    While nonsuperconducting particles are known to serve as effective pinning centers in conventional superconductors, their effect in high T c superconductors is still controversial. In this paper, the author gives evidence that nonsuperconducting Y 2 BaCuO 5 (21 1) inclusions can act as pinning centers in melt processed YBaCuO superconductors even when their size is orders of magnitude larger than the coherence length. In such a case, the interface provides pinning. Theoretical estimates based on direct summations agree well with the experimental results. The applications of direct summation for obtaining the bulk pinning force is justified by direct observation of the FLL (flux line lattice), where the FLL has no long range order and the fluxoids are pinned by 211 inclusions

  19. Temperature dependence of positron lifetime in the two-mixed-phase Bi-Sr-Ca-Cu-O superconductor

    International Nuclear Information System (INIS)

    Zhang, D.M.; Tang, C.Q.; Gen, T.; Li, G.Y.

    1993-01-01

    As compared with the YBaCuO(123) system, the studies of positron annihilation performed for other cuprate superconductors, specifically for the BiSrCaCuO and TlBaCa.CuO systems, are very few. Thus further study of positron annihilation in BiSrCaCuO and TlBaCaCuO systems is necessary. In this note, we report the results of the temperature dependence of positron lifetime parameters in the two-mixed-phase system BiSrCaCuO and discuss the results. (orig.)

  20. Point-contact electron tunneling into the high-T/sub c/ superconductor Y-Ba-Cu-O

    International Nuclear Information System (INIS)

    Kirk, M.D.; Smith, D.P.E.; Mitzi, D.B.

    1987-01-01

    We report results of a study of electron tunneling into bulk samples of the new high-T/sub c/ superconductor Y-Ba-Cu-O using point-contact tunneling. Based on a superconductive tunneling interpretation, the results show exceptionally large energy gaps in these materials (roughly 2Δ = 100 meV), implying 2Δ/k/sub C/T/sub c/--13. Similar values were found previously by us for La-Sr-Cu-O. We also see Structure in the I-V curves similar to that seen in La-Sr-Cu-O. On the basis of the asymmetries observed in the I-V characteristics, we believe that the natural tunneling barrier on this material is of the Schottky type

  1. The flux pinning properties of BaSnO{sub 3}-added GdBa{sub 2}Cu3O{sub 7-δ} films with varying growth conditions

    Energy Technology Data Exchange (ETDEWEB)

    Lee, J. K.; Oh, J. Y.; Kang, B. [Dept. of Physics, Chungbuk National University, Cheongju (Korea, Republic of); Lee, J. M.; Kang, W. N. [Dept. of Physics, Sungkyunkwan University, Suwon (Korea, Republic of)

    2017-09-15

    Addition of BaSnO{sub 3} (BSO) to GdBa{sub 2}Cu{sub 3}O{sub 7-δ} (GdBCO) is reported to enhance the flux pinning property of GdBCO thick films. To investigate the effect of growth condition on the pinning properties, 700 nm-thick BSO-added GdBCO films deposited with varying temperatures and growth rates were prepared by using a pulsed laser deposition method. As the deposition temperature increases, the critical current density and the pinning force density show an improved field dependence up to 750 ℃ due to the increase in the formation of the a-axis growth and the BSO nanostructures. The films deposited at higher temperatures show degraded surfaces and as a result, degraded pinning behaviors. For the change in growth rate, the critical current density and the pinning force increase as the repetition rate increase at low magnetic fields, but this behavior is reversed in high magnetic fields. These results indicate that the film growth conditions significantly affect the formation of BSO nanostructures and the pinning properties of BSO-added GdBCO films.

  2. Critical current density of four-CuO2-layer T1Ba2Ca3Cu4O11-δ

    International Nuclear Information System (INIS)

    Zhang, L.; Liu, J.Z.; Shelton, R.N.

    1998-01-01

    Full text: A key requirement for technological application is to have superconductors with high critical current density at practical operating temperatures and magnetic fields. The critical current density is strongly related to underlying properties of high T c superconductors, such as layering, anisotropy and other intrinsic material structures. The thallium-based superconductors attracted much attention at early stage mainly due to their high superconducting transitions. Recent studies show that these materials appear to be a better choice for achieving higher critical current density because of a stronger interlayer coupling between superconducting layers. Single crystals of TlBa 2 Ca 3 Cu 4 O 11-δ were grown by a self-flux method. This material is a strong-layered superconductor with four-CuO 2 -planes in a unit cell and a superconducting transition temperature of 128K. Our experimental results show that TlBa 2 Ca 3 Cu 4 O 11-δ crystals have high irreversibility line, large critical current density and high upper critical field. The impact of layering and the number of Cu-O layers on flux pinning, critical current density and other magnetic properties will also be discussed

  3. Electronic structure of the Y Ba2 Cu3 O7-x high temperature superconductor ceramic

    International Nuclear Information System (INIS)

    Lima, G.A.R.

    1990-01-01

    We investigate the electronic structure of superconductor Y Ba 2 Cu 3 O 7-x through a molecular cluster approach. The calculations are performed self consistently through a semi empirical L.C.A.O. technique, where different charge states are considered. The correlation effects are taken into account by configuration interaction procedure (INDO/CI). The results for the larger cluster yield a density of states showing a strong p-d covalency resulting in a width of around 8,0 eV for the valence band. The optical excitations is analyzed in detail and compared with the experimental data. (author)

  4. Parasitic phase formation in the La Ba{sub 2} Cu{sub 3} O{sub 7-x} superconductor; Fases parasitas en el superconductor La Ba{sub 2} Cu{sub 3} O{sub 7-x}

    Energy Technology Data Exchange (ETDEWEB)

    Baltra, T [Ministerio de Educacion, Santiago (Chile); Fuenzalida, V M; Grahmann, C R [Chile Univ., Santiago (Chile). Dept. de Fisica

    1997-12-31

    The parasitic phase formation during the thermal processing of the H Tc La Ba{sub 2} Cu{sub 3} O{sub 7-x} superconductor, particularly the Ba Cu O{sub 2}, is studied. The formation of the stable parasitic phase depends on the temperature of the initial treatments and on the heating rate during the sintering process. The superconducting highest purity material is obtained with treatment at 900 deg C and lowest heating rate. The temperature during the final annealing in oxygen of the sample did also affect the transport properties. Samples with the lowest resistivity in the normal state were produced by annealing in oxygen at 300 deg C. The largest orthorhombic distortion was obtained at 325 deg C. (author). 2 refs., 1 fig., 2 tabs.

  5. Enhanced critical currents in (Gd,Y)Ba2Cu3Ox superconducting tapes with high levels of Zr addition

    Energy Technology Data Exchange (ETDEWEB)

    Selvamanickam, V; Chen, Y; Shi, T; Liu, Y; Khatri, ND; Liu, J; Yao, Y; Xiong, X; Lei, C; Soloveichik, S; Galstyan, E; Majkic, G

    2013-01-21

    The critical current and structural properties of (Gd,Y)BaCuO tapes made by metal organic chemical vapor deposition (MOCVD) with Zr addition levels up to 30 at.% have been investigated. The reduction in critical current beyond the previously optimized Zr addition level of 7.5 at.% was found to be due to structural deterioration of the (Gd,Y)Ba2Cu3Ox film. By a modified MOCVD process,enhanced critical current densities have been achieved with high levels of Zr addition,including 3.83 MA cm(-2) in 15 at.% Zr- added 1.1 mu m thick film at 77 K in zero magnetic field. Critical currents as high as 1072 A/ 12 mm have been reached in (Gd,Y) BaCuO tapes with 15 at.% Zr addition at 30 K in a field of 3 T applied perpendicular to the tape,corresponding to a pinning force value of 268 GN m(-3). The enhanced critical currents achievable with a high density of nanoscale defects by employing high levels of second- phase additions enable the performance targets needed for the use of HTS tapes in coil applications involving high magnetic fields at temperatures below 50 K to be met.

  6. Structural instabilities in superconductor Y-Ba-Cu-O studied by positron annihilation

    International Nuclear Information System (INIS)

    Wang Shaojie; Li Xiaohua; Chen Yilong; Li Shiqing; Feng Guohua; Wang Zhu; Chen Ang; Li Biaorong

    1989-01-01

    The positron lifetime and Doppler broadening were measured as a function of temperature between 100K and 300K for Y-Ba-Cu-O superconductor. There are anomalous changes in the positron lifetimes and S parameters near 130K and 260K which imply that some phase transitions related to superconductivity happenned there. The results were discussed in terms of the lattice instabilities which may caused by the ordering readjustment of oxygen vacancies

  7. Pinning performance of (Nd,Eu,Gd)-123 superconductors: Comparison of melt-textured pellet and single crystal

    Czech Academy of Sciences Publication Activity Database

    Jirsa, Miloš; Rameš, Michal; Jurek, Karel; Muralidhar, M.; Das, P.; Koblischka, M.R.; Wolf, T.

    2008-01-01

    Roč. 151, č. 1 (2008), s. 25-30 ISSN 0921-5107 R&D Projects: GA ČR GA202/05/0173; GA MŠk 1P05ME728 Institutional research plan: CEZ:AV0Z10100520 Keywords : high-temperature superconductors * cuprous oxides * superconductivity perovskites, * (Nd,Eu,Gd)BaCuO * ternary compounds * melt-textured materials Subject RIV: BM - Solid Matter Physics ; Magnetism

  8. High-pressure synthesis of CuBa2Ca3Cu4O10+δ superconductor from precursors prepared by a polymerized complex method

    International Nuclear Information System (INIS)

    Aoba, Tomoya; Bizen, Takeshi; Suzuki, Tsuneo; Nakayama, Tadachika; Suematsu, Hisayuki; Niihara, Koichi; Katsumata, Tetsuhiro; Inaguma, Yoshiyuki

    2011-01-01

    Samples of a CuBa 2 Ca 3 Cu 4 O 10+ δ superconductor were synthesized under a high pressure of 5 GPa at 1100-1200degC for 30 min using precursors produced by solid-state reaction and polymerized complex methods. Compared with the precursors prepared by the solid-state reaction method, the precursors produced by the polymerized complex method have low grain sizes. The superconductive transition temperature of the samples prepared using precursors made by the polymerized complex method was found to be 113 K. The volume fractions of the superconducting phase in the samples prepared using precursors made by the solid-state reaction and polymerized complex methods were 49 and 36%, respectively. From these results, precursors made by the polymerized complex method can be used in the high-pressure synthesis of superconductors similarly to those made by the solid-state reaction method. (author)

  9. Structural changes between 100 and 300 K of the high-Tc superconductor Y-Ba-Cu-O studied by positron annihilation

    International Nuclear Information System (INIS)

    Wang, S.J.; Li, X.H.; Chen, Y.L.; Li, S.Q.; Fong, G.H.; Wang, Z.

    1989-01-01

    The structural changes of the high-T c superconductor Y-Ba-Cu-O between 100 and 300 K are studied by positron lifetime and Doppler broadening measurements as a function of temperature. There are anomalous changes in the positron lifetimes and Doppler broadening S-parameters near 130 and 260 K, which is consistent with some reported experimental results. These anomalies may be caused by the lattice instabilities, such as the ordering readjustment of oxygen vacancies. (author)

  10. Hyper- and hypobaric processing of Tl-Ba-Ca-Cu-O superconductors

    Science.gov (United States)

    Goretta, K. C.; Routbort, J. L.; Shi, Donglu; Chen, J. G.; Hash, M. C.

    1989-11-01

    Tl-based superconductors of initial composition Tl:Ca:Ba:Cu equal to 2:2:2:3 and 1:3:1:3 were heated in oxygen at pressures of 10(sup 4) to 6 (times) 10(sup 5) Pa. The 2:2:2:3 composition formed primarily the 2-layer superconductor with zero resistance from 77 to 104 K. The 1:3:1:3 composition formed nearly phase pure 3-layer superconductor with a maximum zero resistance temperature of 120 K. Application of hyperbaric pressure influenced phase purities and transition temperatures slightly; phase purities decreased significantly with application of hypobaric pressures.

  11. The Pr and Ca substitution in GdBa2Cu3O7-8

    International Nuclear Information System (INIS)

    Shakeri, H.; Akhavan, M.

    2002-01-01

    The granular Gd 1 -x-zPr x Ca z Ba 2 Cu 3 O 7 -8 (Gd Pr Ca-123) high-temperature cuprate samples with 0.0≤x≤0.3 and 0.0≤z≤0.35 are prepared by standard solid state reaction and characterized by XRD and SEM techniques. The BaCuO 2 and impurity phases are less than 1% in the samples having high levels of Pr and Ca concentrations. The electrical resistivity measurements show a nonlinear reduction in T c (x,z=etc) versus x. Moreover, the T c (z) curve with x=0 is nonlinear and a plateau appears at z≅0.05-0.015. For Pr-Ca-doped samples with a constant concentration of Pr, T c increases with the increase of Ca up to an optimum value of Ca doping and then in decreases. Based on these observations, we suggest that hole filling and hole localization the main effects of Pr ion substitution. The magnetic measurements indicate that the value of H C 1 is in the order of 10 m T. The magnetoresistance measurements have been measured and analyzed. The superconducting transition region is broadened by the application of magnetic field. The experimental data near the on sen of superconductivity are fitted with the Ambegakor and Halperin (A H) phase-slip model. We observe that the A H parameter, γ(H), depends not only on the temperature and the magnetic field, but also on the Pr and Ca ions concentrations. It is observed that the critical current density increases with Ca substitution and decreases with pr substitution in Gd-123 system. We suggest that the pr ion substitution probably enhances the weak link, but the Ca ion acts as flux pinning center in the Gd Pr Ca-123 system

  12. High Performance Proton-Conducting Solid Oxide Fuel Cells with a Layered Perovskite GdBaCuCoO5+ x Cathode

    Science.gov (United States)

    Zhang, Xiaozhen; Jiang, Yuhua; Hu, Xuebing; Sun, Liangliang; Ling, Yihan

    2018-03-01

    Proton-conducting solid oxide fuel cell (H-SOFC) based on layered perovskite type GdBaCuCoO5+x (GBCC) cathode was fabricated with in situ drop-coating BaZr0.1Ce0.7Y0.2O3-δ (BZCY) electrolyte membrane. The influences of Cu doping into Co sites of GdBaCo2O5+ x on the electrical conductivity and conduction mechanism, thermal expansion property and electrochemical performance of cathode materials and corresponding single cell were investigated. Results show that the electrical conductivity decreased and the conduction mechanism would gradually transform to the semiconductor-like behavior. A high maximum power density of 480 mW cm-2 was obtained for the anode supported NiO-BZCY/NiO-BZCY/BZCY/GBCC single cells with wet H2 fuel at 700 °C. The corresponding polarization resistance was as low as 0.17 Ω cm2. The excellent electrochemical performance of as-prepared single cell indicates that GBCC is a good candidate of cathode materials for H-SOFCs.

  13. Smooth surfaces in very thin GdBa{sub 2}Cu{sub 3}O{sub 7−δ} films for application in superconducting tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Navarro, H., E-mail: henrynavarro@cab.cnea.gov.ar [Instituto Balseiro, Universidad Nacional de Cuyo & CNEA, 8400 Bariloche (Argentina); Centro Atómico Bariloche, Comisión Nacional de Energía Atómica. Av. Bustillo 9500, 8400 San Carlos de Bariloche (Argentina); Sirena, M. [Instituto Balseiro, Universidad Nacional de Cuyo & CNEA, 8400 Bariloche (Argentina); Centro Atómico Bariloche, Comisión Nacional de Energía Atómica. Av. Bustillo 9500, 8400 San Carlos de Bariloche (Argentina); Kim, Jeehoon [Department of Physics, Pohang University of Science and Technology, Pohang (Korea, Republic of); CALDES, Institute for Basic Science, Pohang (Korea, Republic of); Haberkorn, N. [Instituto Balseiro, Universidad Nacional de Cuyo & CNEA, 8400 Bariloche (Argentina); Centro Atómico Bariloche, Comisión Nacional de Energía Atómica. Av. Bustillo 9500, 8400 San Carlos de Bariloche (Argentina)

    2015-03-15

    Highlights: • A detailed study of the morphological properties of GdBa{sub 2}Cu{sub 3}O{sub 7−δ} thin films was realized. • The inclusion of a very thin SrTiO{sub 3} buffer layer modifies the surface of the SrTiO{sub 3} substrates. • The inclusion of the buffer layer suppress the three dimensional nucleation in the GdBa{sub 2}Cu{sub 3}O{sub 7−δ} film. • GdBa{sub 2}Cu{sub 3}O{sub 7−δ} films with large areas free of topological defects and T{sub c} close to liquid nitrogen can be obtained. - Abstract: This paper provides a systematic analysis of the morphology and the superconducting critical temperature obtained in very thin GdBa{sub 2}Cu{sub 3}O{sub 7−δ} films grown on (0 0 1) SrTiO{sub 3} substrates by DC sputtering. We find that the use of a very thin SrTiO{sub 3} buffer layer (≈2 nm) modify the nucleation of GdBa{sub 2}Cu{sub 3}O{sub 7−δ} on the surface of the substrate reducing the formation of 3 dimensional clusters. Our results demonstrate that 16 nm thick GdBa{sub 2}Cu{sub 3}O{sub 7−δ} films with an average root-mean-square (RMS) smaller than 1 nm and large surface areas (up 10 μm{sup 2}) free of 3 dimensional topological defects can be obtained. In films thinner than 24 nm the onset (zero resistance) of superconducting transition of the films is reduced, being close to liquid nitrogen. This fact can be associated with stress reducing the orthorhombicity and slightly drop in oxygen stoichiometry.

  14. Mercury nonstoichiometry of the Hg1-xBa2CuO4+δ superconductor and the P(Hg)-P(O2)-T phase diagram of the Hg-Ba-Cu-O system

    International Nuclear Information System (INIS)

    Alyoshin, V.A.; Mikhailova, D.A.; Rudnyi, E.B.; Antipov, E.V.

    2002-01-01

    The P(Hg)-P(O 2 )-T phase diagram of the Hg-Ba-Cu-O system for the Ba:Cu=2:1 ratio was experimentally studied and followed by means of the thermodynamic modeling. It was shown that the Hg 1-x Ba 2 CuO 4+δ (Hg-1201) superconductor possesses a significant range of Hg-nonstoichiometry and exists in a certain P(Hg), P(O 2 ) and T range. Mercury nonstoichiometry of Hg-1201 was investigated in the 923≤T≤1095 K; 2.0≤P(Hg)≤8.4 atm; 0.09≤P(O 2 )≤0.86 atm ranges. It was found that the mercury content varies in the range of 0.80-0.94 under these conditions. The Gibbs energy of the Hg-1201 phase was estimated as a function of temperature and mercury concentration. The obtained results allow optimizing the synthesis conditions of Hg-1201 with a given Hg-content including preparation of the Hg-stoichiometric phase

  15. Electromagnetic Properties of (Gd, Y)Ba2Cu3Ox Superconducting Tapes With High Levels of Zr Addition

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Y; Yao, Y; Chen, Y; Khatri, ND; Liu, J; Galtsyan, E; Lei, C; Selvamanickam, V

    2013-06-01

    The dependence of the critical current density (J(c)) on the orientation of applied magnetic fields was studied in Zr-doped (Gd, Y)Ba2Cu3Ox tapes fabricated by metal organic chemical vapor deposition. The in-field performance of J(c) of (Gd, Y)Ba2Cu3Ox tapes with Zr-doping levels of 7.5-30 at.% was investigated up to 5 T over a temperature range of 40-77 K. The highest critical currents (I-c) at H parallel to c and the highest values of minimum Ic in angular dependence measurements were achieved in the tapes with 20% Zr doping over a broad range of temperature and magnetic field conditions measured. The electromagnetic properties have been related to the changes in BaZrO3 content and microstructure.

  16. Properties of Y Ba2 Cu3 O7-δ-Ag superconductors prepared by the citrate method

    International Nuclear Information System (INIS)

    Fonseca, F.C.; Muccillo, R.

    1996-01-01

    Y Ba 2 Cu 3 O 7-δ (123) ceramic superconductor and YBa 2 Cu 3 O 7-δ - Ag composite superconductors have been prepared by the citrate method. Microstructural analysis has been done by X-ray diffractometry and optical ceramography. The superconducting behaviour has been studied by 4-probe dc resistivity in the 77 K - 140 K temperature range. Silver percolation in the ceramic matrix was studied by electrical resistivity measurements at room temperature; the percolation threshold was found to be approximately 25 vol% (35.5 wt%) Ag. Specimens with silver addition showed improvement in the flexural strength of the 123 compound. The main results show that the critical temperature does not depend on the silver content in the composite specimens, and that approximately 3 wt% (1.8 vol%) Ag doping yields an optimized composite superconductor from the microstructural point of view, with platelet-like grain shapes. (author)

  17. Thermochemical investigations into the system Y-Ba-Cu-O

    International Nuclear Information System (INIS)

    Neuschuetz, D.; Zimmermann, E.; Hack, K.; Boudene, A.; Mohammad, A.

    1992-01-01

    For a consistent thermodynamic description of the quaternary system Y-Ba-Cu-O, the binary and ternary subsystems must be known. The metallic binaries and the ternary system Y-Ba-Cu have been evaluated by the authors. Discrepancies within the Cu-O system made a thorough experimental re-investigation necessary, leading to a new consistent thermodynamic data set for copper-oxygen which can now serve as a basis for the description of phase equilibria of all high temperature superconductors. Extensive experimental work on the ternaries Y-Cu-O and Ba-Cu-O, which are oxygen partial pressure dependent, revealed liquid phases down to 790degC. The ternary Y-Ba-O could be described more easily on the basis of literature values and present experimental results, because it does not contain any liquid phases at relevant temperatures. The representation of the quaternary Y-Ba-Cu-O is complicated both by its dependence on the oxygen potential and the existence of liquid oxide phases. In contrast to common practice, the present investigations had to start from Cu-free Ba-Y-O in order to avoid unknown liquid phases in the experiments. The present results being insufficient for a complete description of the quaternary system, the work is being continued within an EC joint research project. (orig.) With 84 refs., 8 tabs., 47 figs [de

  18. Positron annihilation studies in the high-temperature superconductors YBa2Cu3Osub(7-x) and HoBa2Cu3Osub(7-x)

    International Nuclear Information System (INIS)

    Mandal, P.; Poddar, A.; Nambissan, P.M.G.; Choudhury, P.; Ghosh, B.; Sen, P.; Majumdar, C.K.

    1988-01-01

    In the high-Tsub(c) superconductors YBa 2 Cu 3 Osub(7-x) and HoBa 2 Cu 3 Osub(7-x) the Doppler-broadened positron annihilation lineshape parameter is studied as a function of temperature. Anomalies are detected around the transition temperature found by resistance measurements, giving indirect support for an electronic mechanism for superconductivity. The positron lifetimes in these compounds are measured at room temperature and are found to be similar. The origins of the several lifetimes found and their intensities are discussed. (author)

  19. The development of research on high temperature superconductors in Malaysia

    International Nuclear Information System (INIS)

    Shaari, A.H.; Hashim, M.; Dalimin, M.N.

    1989-01-01

    The background of the recent discovery of high-temperature oxide superconductor is given. This new discovery has driven scientists of different disciplines from many parts of the world into the race. Even those researchers from the developing countries are able to join the band wagon of the frontier research due to the convenience of working at temperatures well above that of liquid nitrogen. In Malaysia, some aspects of preparations and characterization of Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O ceramics are studied. The 90 K transition temperature is observed in Y-Ba-Cu-O. (Auth.). 10 figs.; 5 refs

  20. Fabrication of single-grain GdBa 2 Cu 3 O 7− bulk ...

    Indian Academy of Sciences (India)

    Research Articles Volume 74 Issue 5 May 2010 pp 827-832 ... Superconductors; top seeded infiltration and growth process; GdBa2 ... The morphology, microstructure and levitation force of the bulk GdBCO have also been investigated.

  1. Pulsed laser deposition of Tl-Ca-Ba-Cu-O films

    International Nuclear Information System (INIS)

    Ianno, N.J.; Liou, S.H.; Woollam, J.A.; Thompson, D.; Johs, B.

    1990-01-01

    Pulsed laser deposition is a technique commonly used to deposit high quality thin films of high temperature superconductors. This paper discusses the results obtained when this technique is applied to the deposition of Tl-Ca-Ba-Cu-O thin films using a frequency doubled Nd:YAG laser operating at 532 nm and an excimer laser operating at 248 nm. Films with onset temperatures of 125 K and zero resistance temperatures of 110 K deposited on (100) oriented MgO from a composite Tl2Ca2Ba2Cu3Ox target were obtained at both wavelengths upon appropriate post deposition annealing. Films deposited at 532 nm exhibit a rough surface, while those deposited at 248 nm are smooth and homogeneous. Upon annealing, films deposited at both wavelengths are single phase Tl2Ca2Ba2Cu3Ox. 12 refs

  2. RE-Ba-Cu-O for high functional superconducting permanent magnet

    International Nuclear Information System (INIS)

    Yoo, S.I.; Higuchi, T.; Sakai, N.; Murakami, M.; Fujimoto, H.

    1998-01-01

    Among various potential applications of melt-textured RE-Ba-Cu-O (REBCO, RE: rare earth elements) superconductors, we have examined the bulk application as the superconducting permanent magnet, especially for the magnetically-levitated (MAGLEV) train. Compared with Y-Ba-Cu-O (YBCO), oxygen-controlled melt-growth (OCMG)-processed LREBCO (LRE: light rare earth elements) bulk superconductors are more promising for this application because of larger critical current density (J c ) values in high field and higher irreversibility field (B irr ) within the range of the liquid nitrogen refrigeration (63-77 K), implying that even higher trapped fields (B t ) are achievable in principle. In this paper, material requirements of superconducting bulks for the MAGLEV train are first presented and then processing aspects for the fabrication of good LREBCO bulks are described. (orig.)

  3. The Pr and Ca Substitution in GdBa2Cu3O7- & delta

    Directory of Open Access Journals (Sweden)

    H. S. H.

    2001-12-01

    Full Text Available   The granular Gd1-x-zPrxCazBa2Cu3O7-δ high-temperature cuprate samples with 0.0 ≤ x ≤ 0.3 and 0.0≤ x ≤ 0.35 are prepared by standard solid state reaction and characterized by XRD and SEM techniques. The BaCuO2 and impurity phases are less than 1% in the samples having high levels of pr and Ca concentrations. The electrical resistivity measurements show a nonlinear reduction in Tc(x,z=etc versus x. Moreover, the Tc(z curve with x=0 is nonlinear and aplateau appears at z≈ 0.05-0.015. For Pr-Ca-doped samples with a constant concentration of Pr, Tc increases with the increase of Ca up to an optimum value of Ca doping and then in decreases. Based on these observations, we suggest that hole filling and hole localization the main effects of Pr ion substiution. The magnetic measurements indicate that the value of Hc1 is in the order of 10 mT. The mangetoresistance measurements have been measured and analyzed. The superconducting transition region is broadened by the application of magnetic field. The experimental data near the onsen of superconductivity are fitted with the Ambegakor and Halperin (AH phase-slip model. We observe that the AH parameter,γ (H, depends not only on the temperature and the magnetic field, but also on the Pr and Ca ions concentrations. It is observed that the critical current density increases with Ca substitution and decreases with Pr substitution in Gd-123 system. We suggest that the Pr ion substitution probably enhances the weak link, but the Ca ion acts as flux pinning center in the GdPrCa-123 system.

  4. High-Tc superconductors under very high pressure

    International Nuclear Information System (INIS)

    Wijngaarden, R.J.; Scholtz, J.J.; Eenige, E.N. van; Griessen, R.

    1991-01-01

    High pressure has played a crucial role in the short history of high T c superconductors. Soon after the discovery of superconductivity by Bednorz and Muller in La-Ba-Cu-O, Chu et al. showed that the critical temperature T c could be significantly increased by pressure. This observation led to the discovery of YBa 2 Cu 3 O 7 by Wu et al. with a T c above 90 K. Incidentally, this high T c is probably also due to the fact that YBa 2 Cu 3 O 7 has two CuO 2 layers per unit cell instead of a single one in La-Ba-Cu-O. The authors discuss the high pressure dependence of the oxide superconductors, particularly at pressures above 10 GPa, and the nonmonotonic dependence of transition temperature on pressure

  5. Crystallographic and electrical properties of Pr substituted Gd-123 nanometre sized high temperature superconductors

    International Nuclear Information System (INIS)

    Huse, V.R.; Mote, V.D.; Shah, S.S.; Dole, B.N.; Purushotham, Y.; Dhar, S.K.

    2011-01-01

    The samples of Gd 1-x Pr x Ba 2 Cu 3 O 7-δ with compositions x = 0.0, 0.1 and 0.3 were prepared by ceramic route. The XRD study of all samples is carried out. The XRD studies of the samples prepared by ceramic route show GdPr-123 system have an orthorhombic perovskite structure. The lattice parameters, oxygen content, volume of unit cell, orthorhombic perovskite structure. The lattice parameters, oxygen content, volume of unit cell, orthorhombic distortion, hole concentration in CuO 2 plane and charge on Cu-O plane were evaluated using XRD data. It is found that the lattice parameters, volume of unit cell increase while oxygen content orthorhombic distortion, hole concentration (Psh) and average charge (p) decrease as doping percentage of Pr increases. The resistivity measurement shows the transition temperature decreases while transition width increases with increasing Pr concentration. The suppression of superconductivity may be due to reduction in hole concentration or magnetic pair breaking. We report such qualitative results of Pr substituted Gd-123 in this paper quantitatively. (author)

  6. Tricrystal tunneling evidence for d-wave pairing symmetry in cuprate superconductors

    International Nuclear Information System (INIS)

    Tsuei, C.C.; Kirtley, J.R.

    1997-01-01

    Strong evidence for d-wave pairing symmetry in high-temperature superconductors such as YBa 2 Cu 3 O 7 and Tl 2 Ba 2 CuO 6+δ has been obtained by monitoring the presence or absence of the half-integer flux quantum effect in various controlled - orientation tricrystal superconducting systems. New results of a tricrystal tunneling experiment with Gd Ba 2 Cu 3 O 7 will also be presented. (orig.)

  7. Process of preparing superconductive oxide complexes containing L, Ba, Cu and O and method of using the same

    International Nuclear Information System (INIS)

    Salama, K.; Selvamanickam, V.

    1995-01-01

    A superconductor material having a current density, J, of from about 30,000 to about 85,000 amps/cm 2 at zero magnetic field and 77 K is disclosed. The 123 superconductor, of the formula L 1 Ba 2 Cu 3 O 6+δ wherein L is preferably yttrium, is capable of entrapping sufficiently high magnetic fields and exhibits a low microwave surface resistance. The process of preparing the superconductor comprises compacting the bulk product, L 1 Ba 2 Cu 3 O, and then sintering the reaction product at a temperature between about 40 C to about 90 C below its melting point, i.e., for Y 1 Ba 2 Cu 3 O 6+δ at a temperature of approximately 940 C. The composition is then heated in a preheated chamber maintained at approximately 1090 C to about 1,200 C (approximately 1,100 C for Y 1 Ba 2 Cu 3 O 6+δ ) until it has been decomposed, and is then rapidly cooled to a temperature between about 10 C to about 30 C above its melting point, i.e. for Y 1 Ba 2 Cu 3 O 6+δ a temperature of 1,030 C, and then is controlled cooled at a rate of 1 C/hr until it reaches a temperature of about 20 C to about 40 C below its melting point, i.e., for Y 1 Ba 2 Cu 3 O 6+δ a temperature of 980 C. The composition is steadily held at this temperature for at least eight hours, and then cooled to a temperature of approximately 400 C below its melting point (for Y 1 Ba 2 Cu 3 O 6+δ approximately a temperature of 600 C). The material is then slowly cooled by another 200 C and is then annealed in oxygen. 5 figs

  8. Superconductivity in the U(Th)-Y-Ba-Cu-O systems

    International Nuclear Information System (INIS)

    Qin Qizong; He Adi; Jia Weijie; Ma Lidun; Cheng Huansheng; Hua Zhongyi

    1989-01-01

    High T c superconductivity has been observed both resistively and magnetically in the new U(Th)-Y-Ba-Cu-O systems. The zero resistance temperature of the three samples with nominal composition of U 0.1 Y 1.1 Ba 0.8 Cu O 4-z , U 0.15 Y 1.05 Ba 0.8 Cu 4-z and Th 0.3 Y 0.8 Ba 0.8 Cu 4-z is 87K, 79K and 74K, respectively. The result of ac magnetic susceptibility measurement implies that the superconducting state is realized in the U-doped samples below 90K. The stoichimetry of the U-Y-Ba-Cu O superconductors has the aid of Rutherford backscattering and nuclear reaction 16 O(d, p) 17 O. The analytical results show that the 'real composition' of somples may be different from that of the nomial composition. The X ray diffraction analysis of the U-Y-Ba-Cu-O system shows that none of the peaks can be fitted to the uranium oxides and the other raw materiale structure, and its pattern may be attributed to new multiple phases with structure different from the known singlephase superconducting oxides

  9. Determining superconducting parameters from analysis of magnetization fluctuation for CaLaBaCu3O7-δ superconductor

    International Nuclear Information System (INIS)

    Parra Vargas, C.A.; Landinez Tellez, D.A.; Roa-Rojas, J.

    2007-01-01

    In this work, we report analysis of magnetization fluctuations for the CaLaBaCu 3 O 7- δ superconducting system. We describe a procedure for extracting the penetration depth λ(T) and the coherence length ξ parameters from the magnetization, as a function of the applied magnetic field. This procedure takes the vortex fluctuation into account. The data of the magnetization excess ΔM(T) are analyzed for different values of temperature in the interval from 65 to 73 K. For several magnetic fields we observed a crossover in the magnetization curves at the characteristic temperature value T *=72.2 K. We calculated the data of magnetization excess from the curves of magnetization as a function of the logarithm of the applied field. This procedure was performed for polycrystalline samples of CaLaBaCu 3 O 7- δ by using the proposition of Bulaevskii, Ledvij and Kogan. We notice that the values for these superconducting parameters are in agreement with reports for high-temperature superconductors

  10. Changes of soft X-ray emission spectra of oxygen and copper in high Tc superconductors

    International Nuclear Information System (INIS)

    Fukushima, Sei; Gohshi, Yohichi; Kohiki, Shigemi; Saitoh, Naoki

    1989-01-01

    X-ray induced soft X-ray emission spectroscopy is one of the bulk analysis methods used to characterize high-Tc superconductor. In this report, some observations on the changes in O Kα and Cu L spectra of thin layer LnBa 2 Cu 3 O 7-δ (Ln=Er,Gd) samples are presented. From the measurement of O Kα, no discernible difference was found between those of Gd compounds which were composed single phase or not. It may be said that the electronic structure of p state localized on the O is not sensitive to the change of Tc or zero-resistance temperature. From the measurement of Cu L spectra, it was found that Cu Lα of only Gd containing compounds has a low energy shoulder

  11. The local structure of high-temperature superconductors

    International Nuclear Information System (INIS)

    Mustre de Leon, J.; Conradson, S.D.; Bishop, A.R.; Raistrick, I.D.

    1992-01-01

    We show how x-ray absorption fine structure (XAFS) has been successfully used in the determination of the local crystal structure of high-temperature superconductors, with advantages over traditional diffraction techniques. We review the experimental results that yielded the first evidence for an axial-oxygen-centered lattice instability connected with the superconductivity transition. The interpretation of this instability in terms of a dynamical tunneling model suggests the presence of polarons in these materials. XAFS on Tl 2 Ba 2 CuO 6 and other Tl-based superconductors indicate the presence of local instabilities in the CuO 2 planes of these materials, in addition to axial-oxygen instabilities

  12. Fluctuation-induced conductivity in melt-textured Pr-doped YBa2Cu3O7-δ composite superconductor

    DEFF Research Database (Denmark)

    Opata, Yuri Aparecido; Monteiro, João Frederico Haas Leandro; Siqueira, Ezequiel Costa

    2018-01-01

    In this study, the effects of thermal fluctuations on the electrical conductivity in melt-textured YBa2Cu3O7-δ, Y0.95Pr0.05Ba2Cu3O7-δ and (YBa2Cu3O7-δ)0.95–(PrBa2Cu3O7-δ)0.05 composite superconductor were considered. The composite superconductor samples were prepared through the top seeding method...... using melt-textured NdBa2Cu3O7-d seeds. The resistivity measurements were performed with a low-frequency, low-current AC technique in order to extract the temperature derivative and analyze the influence of the praseodymium ion on the normal superconductor transition and consequently on the fluctuation...

  13. Growth of high-temperature superconductor crystals from flux

    International Nuclear Information System (INIS)

    Demianets, L.N.; Bykov, A.B.; Melnikov, O.K.; Stishov, S.M.

    1991-01-01

    Crystallization of high-temperature superconductors was studied in La-Sr-Cu-O, Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O systems. Platelet crystals YBa 2 Cu 3 Osub(6.5+x) were obtained by spontaneous crystallization from homogeneous nonstoichiometric melts enriched in barium and copper oxides. Lasub(2-x)Sr x CuO 4 was prepared by slow cooling of melts enriched in copper oxide. Bi 2 (Sr, Ca)sub(n+1)Cu n O y , (n=1;2) was obtained by melting zone travelling. The crystals show transition to superconducting state at T=93K, ΔT 0.2-0.5 K (Y, Ba cuprate), T=87K, ΔT 2K (Bi, Sr, Ca-cuprate). La, Sr-cuprate single crystals obtained by Czochralski method did not show transition to superconducting state. For flux-grown crystals T c was 5-26 K depending on the composition, growth and heat treatment. The short characterization of some accessory phases (Ba 3 Y 2 Cu 3 PtO 10 , Casub(1.75)Srsub(1.5)Cusub(0.75)PtO 6 , BaCuO 2 , Ba 41 Cu 44 O 84 Cl 2 ) is reported. (author). 15 ref s., 8 figs

  14. Synthesis of high-oxidation Y-Ba-Cu-O phases in superoxygenated thin films

    Science.gov (United States)

    Zhang, H.; Gauquelin, N.; McMahon, C.; Hawthorn, D. G.; Botton, G. A.; Wei, J. Y. T.

    2018-03-01

    It is known that solid-state reaction in high-pressure oxygen can stabilize high-oxidation phases of Y-Ba-Cu-O superconductors in powder form. We extend this superoxygenation concept of synthesis to thin films which, due to their large surface-to-volume ratio, are more reactive thermodynamically. Epitaxial thin films of YBa2Cu3O7 -δ grown by pulsed laser deposition are annealed at up to 700 atm O2 and 900 ∘C , in conjunction with Cu enrichment by solid-state diffusion. The films show the clear formation of Y2Ba4Cu7O15 -δ and Y2Ba4Cu8O16 as well as regions of YBa2Cu5O9 -δ and YBa2Cu6O10 -δ phases, according to scanning transmission electron microscopy, x-ray diffraction, and x-ray absorption spectroscopy. Similarly annealed YBa2Cu3O7 -δ powders show no phase conversion. Our results demonstrate a route of synthesis towards discovering more complex phases of cuprates and other superconducting oxides.

  15. Strong pinning in very fast grown reactive co-evaporated GdBa2Cu3O7 coated conductors

    Directory of Open Access Journals (Sweden)

    J. L. MacManus-Driscoll

    2014-08-01

    Full Text Available We report on compositional tuning to create excellent field-performance of Jc in “self-doped,” GdBa2Cu3O7−y (GdBCO coated conductors grown by ultrafast reactive co-evaporation. In order to give excess liquid and Gd2O3, the overall compositions were all Ba-poor and Cu-rich compared to GdBCO. The precise composition was found to be critical to the current carrying performance. The most copper-rich composition had an optimum self-field Jc of 3.2 MA cm−2. A more Gd-rich composition had the best in-field performance because of the formation of low coherence, splayed Gd2O3 nanoparticles, giving Jc (77 K, 1 T of over 1 MA cm−2 and Jc (77 K, 5 T of over 0.1 MA cm−2.

  16. Controlled levitation of Y-Ba-Cu-O bulk superconductors and energy minimum analysis; Y-Ba-Cu-O baruku chodendotai no fujo to enerugi kaiseki

    Energy Technology Data Exchange (ETDEWEB)

    Magashima, K. [Railway Technical Research Institute, Tokyo (Japan); Iwasa, Y. [Francis Bitter Magnet Laboratory, Canbridge (United States); Sawa, K. [keio University, Tokyo (Japan); Murakami, M. [Superconductivity research Laboratory, Tokyo (Japan)

    1999-11-25

    The levitation of bulk Y-Ba-Cu-O superconductors can be controlled using a Bi-Sr-Ca-Cu-O (Bi2223) superconducting electromagnet. It was found that stable levitation without tilting could be obtained only when the sample trapped a certain amount of fields, the minimum of which depended on the external field and sample dimensions. We employed a novel analysis method for levitation based on the total energy balance, which is much simpler than the force method and could be applied to understanding general levitation behavior. Numerical analyses thus developed showed that stable levitation of superconductors with large dimensions cen only be achieved when the induced currents can flow with three-dimensional freedom. (author)

  17. Passivation of high temperature superconductors

    Science.gov (United States)

    Vasquez, Richard P. (Inventor)

    1991-01-01

    The surface of high temperature superconductors such as YBa2Cu3O(7-x) are passivated by reacting the native Y, Ba and Cu metal ions with an anion such as sulfate or oxalate to form a surface film that is impervious to water and has a solubility in water of no more than 10(exp -3) M. The passivating treatment is preferably conducted by immersing the surface in dilute aqueous acid solution since more soluble species dissolve into the solution. The treatment does not degrade the superconducting properties of the bulk material.

  18. Superconductivity above 90K in the Y-Ba-Cu-O compound system

    International Nuclear Information System (INIS)

    Paterno, G.; Balestrino, G.; Barbanera, S.

    1987-01-01

    Preliminary results on high Tc superconductors are reported. One of Y-Ba-Cu-O compound system has been fabricated. The temperature dependence of the resistance has been determined. The critical temperature of the samples annealed in Oxygen atmosphere is well above the normal boiling point of liquid nitrogen

  19. Effect of crystalline electric field on heat capacity of LnBaCuFeO5 (Ln = Gd, Ho, Yb)

    Science.gov (United States)

    Lal, Surender; Mukherjee, K.; Yadav, C. S.

    2018-02-01

    Structural, magnetic and thermodynamic properties of layered perovskite compounds LnBaCuFeO5 (Ln = Ho, Gd, Yb) have been investigated. Unlike the iso-structural compound YBaCuFeO5, which shows commensurate antiferromagnetic to incommensurate antiferromagnetic ordering below ∼200 K, the studied compounds do not show any magnetic transition in measured temperature range of 2-350 K. The high temperature heat capacity of the compounds is understood by employing contributions from both optical and acoustic phonons. At low temperature, the observed upturn in the heat capacity is attributed to the Schottky anomaly. The magnetic field dependent heat capacity shows the variation in position of the anomaly with temperature, which appears due to the removal of ground state degeneracy of the rare earth ions, by the crystalline electric field.

  20. Positron annihilation study on Y-Ba-Cu-O high Tc superconductors

    International Nuclear Information System (INIS)

    Balogh, A.G.; Liszkay, L.; Molnar, B.; Puff, W.

    1987-08-01

    First positron annihilation measurements are reported on high T c superconductor YBa 2 Cu 3 O 7-x . The lifetime and Doppler broadening spectra show a slight but significant change about 240K suggesting a deviation from the normal structure far above 90K where the resistance falls to zero. (author)

  1. Method for preparation of textured YBa.sub.2 Cu.sub.3 O.sub.x superconductor

    Science.gov (United States)

    Selvamanickam, Venkat; Goyal, Amit; Kroeger, Donald M.

    1998-01-01

    The present invention relate to textured YBa.sub.2 Cu.sub.3 O.sub.x (Y-123) superconductors and a process of preparing them by directional recrystallization of compacts fabricated from quenched YBCO powders at temperatures about 100.degree. C. below the peritectic temperature to provide a superconductor where more than 75% of the YBa.sub.2 Cu.sub.3 O.sub.x phase is obtained without any Y.sub.2 BaCuO.sub.5 .

  2. High pressure study of high temperatures superconductors: Material base, universal Tc-behavior, and charge transfer

    International Nuclear Information System (INIS)

    Chu, C.W.; Hor, P.H.; Lin, J.G.; Xiong, Q.; Huang, Z.J.; Meng, R.L.; Xue, Y.Y.; Jean, Y.C.

    1991-01-01

    The superconducting transition temperature (T c ) has been measured in YBa 2 Cu 3 O 6.7 , YBa 2 Cu 3 O 7 , Y 2 Ba 4 Cu 7 O 15 , YBa 2 Cu 4 O 8 , Tl 2 Ba 2 Ca n-1 Cu n O n+4-δ , La 2-x Sr x CuO 4 , and La 2-x Ba x CuO 4 under high pressures. The pressure effect on the positron lifetime (τ) has also been determined in the first four compounds. Based on these and other high pressure data, the authors suggest that (1) all known cuprate high temperature superconductors (HTS's) may be no more than mere modifications of either 214-T, 214-T', 123, or a combination of 214-T' and 123, (2) a nonmonotonic T c -behavior may govern the T c -variation of all hole cuprate HTS's and (3) pressure can induce charge transfer leading to a T c -change. The implications of these suggestions will also be discussed

  3. Glass precursor approach to high-temperature superconductors

    Science.gov (United States)

    Bansal, Narottam P.

    1992-01-01

    The available studies on the synthesis of high T sub c superconductors (HTS) via the glass precursor approach were reviewed. Melts of the Bi-Sr-Ca-Cu-O system as well as those doped with oxides of some other elements (Pb, Al, V, Te, Nb, etc.) could be quenched into glasses which, on further heat treatments under appropriate conditions, crystallized into the superconducting phase(s). The nature of the HTS phase(s) formed depends on the annealing temperature, time, atmosphere, and the cooling rate and also on the glass composition. Long term annealing was needed to obtain a large fraction of the 110 K phase. The high T sub c phase did not crystallize out directly from the glass matrix, but was preceded by the precipitation of other phases. The 110 K HTS was produced at high temperatures by reaction between the phases formed at lower temperatures resulting in multiphase material. The presence of a glass former such as B2O3 was necessary for the Y-Ba-Cu-O melt to form a glass on fast cooling. A discontinuous YBa2Cu3O(7-delta) HTS phase crystallized out on heat treatment of this glass. Attempts to prepare Tl-Ba-Ca-Cu-O system in the glassy state were not successful.

  4. Superconductivity degradation in Gd-containing high temperature superconductors (HTSC) under thermal neutron irradiation

    International Nuclear Information System (INIS)

    Petrov, A.; Kudrenitskis, I.; Makletsov, A.; Arhipov, A.; Karklin, N.

    1999-01-01

    The physical properties of ordered crystals are extremely sensitive to the degree of order in the distribution of the various kinds of atoms over the corresponding sites in the crystal lattice. An increasingly popular means of creating disordered states is to use nuclear radiation. The type of radiation defects which appear and the nature and degree of the structural changes in ordered crystals depend on the kind of radiation and the fluence level, the irradiation temperature, the type of crystal structure, the composition and initial disorder of the material, the character of the interatomic forces, etc. There are many such scientific publications where the effects of fast neutron irradiation on high temperature superconductors (HTSC) have been studied in both polycrystalline and single crystalline superconductors. It is known also that the role of thermal neutrons in structural defects forming is negligible in comparison with fast neutrons because of their small (∼0.025 eV) energy. But it is evident enough that in superconductors containing isotopes with large thermal neutron cross sections the important results concerning the role of point defects could be obtained. Such point defects are creating due to soft displacements of isotopes having interacted with thermal neutrons. Such the possibility of creating point defects in solids including HTSC is investigating by several groups (Austria, USA, China, Latvia) and these investigations have found the support in the person of IAEA. In this review the authors consider the changes brought about by thermal-neutron irradiation (E∼0.025 eV) in the structure, superconducting and magnetic properties of gadolinium containing ordered HTSC with the structure 123, whose extreme electric and magnetic properties continue to attract both research and practical interest. All of the studies reviewed have been done on bulk polycrystalline samples RBa 2 Cu 3 O 7-δ (where R - natural mixture of Gd isotopes, 155 Gd, 157 Gd, 160

  5. Pure and Y-substituted BaZrO3 ceramics. A possible support material for fabrication of YBa2Cu3O7-x high-Tc superconductors

    International Nuclear Information System (INIS)

    Wang Xiandong.

    1993-01-01

    This thesis concerns the preparation and characterization of cuprate based high-T c superconductors (Y-123 and Bi-2223) and especially development and testing of BaZrO 3 based materials. The formation of YBa 2 Cu 3 O y (Y-123) by a CO 2 -free route involving reaction sintering of stoichiometric mixtures of chemically prepared fine powders of Y 2 BaCuO 5 , BaCuO 2 and CuO have been studied by thermal and XRD analysis. The synthesis and sintering of BaZrO 3 powders prepared by the hydroxide-alkoxide-methanol sol-gel route have been studied. The phase relations in the system BaO-Y 2 O 3 -ZrO 2 have been studied to determine the solid solubility limits for the perovskite phase Ba X Y Y Zr Z O N (X+X+Z=3) at 1500 deg. C. In the binary system Y 2 O 3 -BaZrO 3 the solubility limit was found to be ≅19 mol% Y 2 O 3 , i.e. Ba 0.81 Y 0. 4 2 Zr 0.81 O 3 . along the joint BaYO 2.5 -Ba the boundary was determined to be at BaY 0.21 Zr 0 . 79 O 2.895 . evidence for a new solid solution series between Ba 3 Y 4 O 9 and ZrO 2 are given, and a partial 1500 deg. C phase diagram for the ternary system BaO-Y 2 O 3 -ZrO 2 is presented. The growth of BaZrO 3 single crystals have been attempted both by a laser zone floating technique and flux methods. The compatibility between YBa 2 Cu 3 O 7 -X and BaZrO 3 , Ba X Y Y Zr Z O 3-δ as well as BaHfO 3 have been studied at 950 deg. and 1050 deg. C. The results show the four most promising candidates as support materials for fabrication of YBa 2 Cu 3 O y to be BaHfO 3 , BaY 0.05 Zr 0.95 O 2.975 , , BaZrO 3 and BaY 0.1 Zr 0.9 O 2.95 . (EG)

  6. A.c. susceptibility measurements in the presence of d.c. magnetic fields for Nd-Ba-Cu-O superconductors

    International Nuclear Information System (INIS)

    Watahiki, M.; Murakami, M.; Yoo, S.I.

    1997-01-01

    We report the temperature and magnetic field dependence of the complex a.c. susceptibility with bias d.c. magnetic fields for melt-processed Nd-Ba-Cu-O superconductor. The onset temperature (T onset ) of the real part of a.c. susceptibility shifted to a lower temperature with increasing d.c. magnetic field. The superconducting transition temperature (T c ) determined by d.c. magnetization measurements did not shift appreciably to a lower-temperature region with increasing d.c. magnetic field. The distinction between T onset and T c indicates that the a.c. susceptibility measurements detect the energy dissipation generated by the motion of flux lines. We have also measured flux profiles and found that there was no appreciable change in flux penetration below and above the peak field, which suggests that the peak effect in Nd-Ba-Cu-O is not due to the phase transition in the flux line lattice. (author)

  7. High homogeneity powder of Ti-Ba-Ca-Cu-O (2223) prepared by Freeze-Drying method

    International Nuclear Information System (INIS)

    Al-Shakarchi, Emad Kh.; Toma, Ziad A.

    1999-01-01

    Full text.Homogeneous high temerature superconductor ceramic powder of TI-Ba-Ca-Cu-O with transition temperature [Tc=123K] have been successfully prepared from the mixture of nitrate salts [TlNO 3 , Ba(NO 3 ) 2 , Ca(NO 3 ) 2 .4H 2 O and Cu(NO 3 ) 2 .3H 2 O] by using freeze-drying method. Freeze-dryer that was used in this work designed locally in our laboratory. This technique consider a better to get a fine powder of ceramic materials by depending on the procedure of frozen droplets with present of liquid nitrogen. SEM pictures showed the size of grains of about [0.8 μm]. We conclude that the high sintering temperature, for the prepared powders in this technique, for long time [120 hrs] will increase the inter diffusion between the grains ahich caused the decreasing in the density of the sample which may be given a better results than the obtained in a previous works

  8. Trapped magnetic field of a superconducting bulk magnet in high- Tc RE-Ba-Cu-O

    International Nuclear Information System (INIS)

    Fujimoto, Hiroyuki; Yoo, Sang Im; Higuchi, Takamitsu; Nakamura, Yuichi; Kamijo, Hiroki; Nagashima, Ken; Murakami, Masato

    1999-01-01

    Superconducting magnets made of high-T c superconductors are promising for industrial applications. It is well known that REBa 2 Cu 3 O 7-x and LRE (light rare-earth) Ba 2 Cu 3 O 7-x superconductors prepared by melt processes have a high critical current density, J c , at 77 K and high magnetic fields. Therefore, the materials are very prospective for high magnetic field application as a superconducting permanent/bulk magnet with liquid-nitrogen refrigeration. LREBaCuO bulks, compared with REBaCuO bulks, exhibit a larger J c in high magnetic fields and a much improved irreversibility field, H irr , at 77 K. In this study, we discuss the possibility and trapped field properties of a superconducting bulk magnet, as well as the melt processing for bulk superconductors and their characteristic superconducting properties. One of the applications is a superconducting magnet for the future magnetically levitated (Maglev) train

  9. The low-temperature, high-magnetic-field critical current characteristics of Zr-added (Gd, Y)Ba2Cu3Ox superconducting tapes

    Energy Technology Data Exchange (ETDEWEB)

    Selvamanickam, V; Yao, Y; Chen, Y; Shi, T; Liu, Y; Khatri, ND; Liu, J; Lei, C; Galstyan, E; Majkic, G

    2012-10-26

    Critical current performances of state-of-the-art Zr-added (Gd, Y)BaCuO tapes have been investigated over a temperature range of 20-77 K, in magnetic fields up to 9 T and over a wide angular range of magnetic field orientations. The peak in critical current that is commonly observed in the field orientation perpendicular to the tape in BaZrO3 (BZO) containing superconducting tapes is found to vanish at 30 K in magnetic fields at 1-9 T. While the critical current of 15% Zr-added tapes was about 40% lower than that of 7.5% Zr-added tapes at 77 K, the pinning force values of the former were found to be 18-23% higher than those of the latter in the temperature range of 20-40 K and in magnetic fields of 3-5 T. The results from this study emphasize the importance of optimization of coated conductor fabrication processes for optimum performance not just in low magnetic fields at 77 K but also at the operating conditions of low temperatures and high magnetic fields that are of interest, especially for rotating superconducting machinery applications.

  10. The low-temperature, high-magnetic-field critical current characteristics of Zr-added (Gd,Y)Ba2Cu3Ox superconducting tapes

    International Nuclear Information System (INIS)

    Selvamanickam, V; Yao, Y; Shi, T; Liu, Y; Khatri, N D; Liu, J; Galstyan, E; Majkic, G; Chen, Y; Lei, C

    2012-01-01

    Critical current performances of state-of-the-art Zr-added (Gd, Y)BaCuO tapes have been investigated over a temperature range of 20–77 K, in magnetic fields up to 9 T and over a wide angular range of magnetic field orientations. The peak in critical current that is commonly observed in the field orientation perpendicular to the tape in BaZrO 3 (BZO) containing superconducting tapes is found to vanish at 30 K in magnetic fields at 1–9 T. While the critical current of 15% Zr-added tapes was about 40% lower than that of 7.5% Zr-added tapes at 77 K, the pinning force values of the former were found to be 18–23% higher than those of the latter in the temperature range of 20–40 K and in magnetic fields of 3–5 T. The results from this study emphasize the importance of optimization of coated conductor fabrication processes for optimum performance not just in low magnetic fields at 77 K but also at the operating conditions of low temperatures and high magnetic fields that are of interest, especially for rotating superconducting machinery applications. (paper)

  11. Investigation of magnetic properties of superconductors Y0.98 - x Cax Co0.02 Ba2 Cu3O7 - δ

    Science.gov (United States)

    Pourasad, Sepideh; Shakeripour, Hamideh; Hosseini, SeyedSajad; Salamati, Hadi

    2018-06-01

    The effect of Co2+, 3+ and Ca2+ substitution in Y3+ site in YBa2Cu3O7-δ superconductor has been studied. The series of high temperature superconducting samples of Y1-y-xCoyCaxBa2Cu3O7-δ with 0 ≤ x ≤ 0.015 and y = 0.020 were prepared by solid-state reaction method. The samples were characterized for phase purity and lattice parameter variations by X-ray diffraction. The AC susceptibility curves, χ'(T), show that in reserving cobalt fixed sample with the optimum Tc, by substitution of divalent Ca2+ at the trivalent Y3+ site no sensitive increasing happen in the superconducting transition temperature.

  12. ESR, SIMS and TEMF of an Y-Ba-Cu-O superconductor

    Science.gov (United States)

    Kirschner, I.; Giber, J.; Halasz, I.

    1995-01-01

    Superconducting transition comes into being between 92 K and 82 K in the samples having a Meissner's state value of 68 vol. percent. The main material content has an orthorhombic unit cell of Y1Ba2Cu408 accompanied by low quantity CuO and a sporadic phase. A proof of anisotropic superconductivity, an unusually high Cu ion concentration and a temperature dependent transition of charge carriers have been observed.

  13. Fabrication and properties of Y-Ba-Cu-O high Tc superconductor by upset-forging method

    International Nuclear Information System (INIS)

    Chang, Ho Jung; Kang, Kae Myung; Song, Jin Tae

    1990-01-01

    YBa 2 Cu 3 O 7-x oxide superconductors was fabricated by sintering process and upset-forging method, respectively, and microstructures and conduction properties were compared. There was no difference in crystal structure the (001) x-ray reflection presumably due to preferred crystal orientation of the YBa 2 Cu 3 O 7-x superconductor. Furthermore, the grain size of the 123-phase increased as the reduction ratio became larger during the upset-forging. The critical temperature for zero resistivity of both samples was almost the same, i.e., about 90K. These results have demonstrated the potential of producing YBa 2 Cu 3 O 7-x superconducting wire or tape effectively using a upset-forging method. The critical current density of the upset-forged sample, however, was lower than that of the sintered one, which fact might be ascribed to microcrack formation during fast upset-forging. (Author)

  14. Mechanical properties of Nd-Ba-Cu-O bulk superconductors

    International Nuclear Information System (INIS)

    Matsui, Motohide; Sakai, Naomichi; Murakami, Masato; Osamura, Kozo

    2003-01-01

    We investigated the effects of Nd422 and Ag particles on the mechanical properties in Nd-Ba-Cu-O bulk superconductors. Both Nd422 and Ag particles were effective in decreasing the amount of microcracks running along the c direction. In the case of Nd422, however, excessive Nd422 addition enhanced the crack propagation, resulting in the degradation of mechanical strength. In the case of Ag addition, the beneficial effect of its ductile mechanical property was not observed. This was due to a relatively large size of Ag particles and low interfacial strength between Ag and Nd123 matrix. It was remarkable that the Weibull coefficient of the sample with Ag 2 O addition exceeded 13, which is reliable enough for practical engineering applications

  15. Gadolinium substitution for yttrium and chemical preparation effects in YBa{sub 2}Cu{sub 3}O{sub 7}: an EPR study; Effets de la substitution de l`yttrium par le gadolinium et de la preparation chimique dans YBa{sub 2}Cu{sub 3}O{sub 7}: etude par RPE

    Energy Technology Data Exchange (ETDEWEB)

    Bejjit, L.; Haddad, M. [Faculte des Sciences, Meknes (Morocco); Bejjit, L. [Faculte des Sciences, Errachidia (Morocco); Deville, A.; Gaillard, B.; Noel, H. [Universite de Provence, 13 - Marseille (France); Monnereau, O. [Universite de Rennes, 35 - Rennes (France)

    1998-01-01

    Compounds with yttrium totally or partially substituted by gadolinium in High-T{sub c} superconductor YBa{sub 2}Cu{sub 3}O{sub 7} were prepared. The superconductivity is not affected by this substitution. An orthorhombic structure has been observed in GdBa{sub 2}Cu{sub 3}O{sub 7} sintered and single crystals. The EPR measurements show linewidth dependence on chemical preparation in GdBa{sub 2}Cu{sub 3}O{sub 7}. In Gd-low concentration compounds (x{<=}0.02), a narrow parasite signal, due to the Y{sub 2}BaCuO{sub 5} green phase, appears superimposed to the principal Gd{sup 3+} ions Electron Spin Resonance (EPR) line. (authors) 12 refs.

  16. X-ray photo-emission studies of Cu1-xTlxBa2Ca3Cu4O12-y superconductor thin films

    International Nuclear Information System (INIS)

    Khan, Nawazish A.; Mumtaz, M.; Ahadian, M.M.; Iraji-zad, Azam

    2006-01-01

    X-ray photo-emission spectroscopy (XPS) studies of Cu 1-x Tl x Ba 2 Ca 3 Cu 4 O 12-y superconductor thin films have been carried out for understanding the mechanism of superconductivity and to find out the reasons for the increase of zero resistivity critical temperature T c (R = 0) with post-annealing in a nitrogen atmosphere. It is observed from these studies that reduction of charge state of thallium is a source of doping of carriers to the CuO 2 planes. The reduced charge state of thallium (i.e. Tl 1+ ) promotes lower oxygen concentration in the charge reservoir layer, which possibly results in movement of electrons to the conducting CuO 2 planes. The higher density of electrons in the CuO 2 planes optimizes the hole concentration 'n p ' in these planes. The reduced charge state of thallium in the Cu 1-x Tl x Ba 2 O 4-δ charge reservoir layer is also supported by a shift of the Ba 3d 5/2 and Ba 3d 3/2 XPS lines to lower binding energies with post-annealing in nitrogen atmosphere. Moreover, the movement of the valance band spectrum to lower binding energies suggested that the electronic density of states changes in the valance band with the post-annealing in nitrogen, which possibly becomes a source of doping of carriers to the CuO 2 planes. The increased doping of electrons to the CuO 2 planes optimizes the Fermi-vector K F and Fermi-velocity V F of the carriers and increases the T c (R = 0) of final compound

  17. Accurate determination of the composition of Y-Ba-Cu-O superconductor by spectrophotometry, gravimetry and flame AAS

    International Nuclear Information System (INIS)

    Bruneel, E; Verbauwhede, D; Vyver, D Van de; Schaubroeck, J; Hoste, S; Driessche, I Van

    2005-01-01

    A procedure for the accurate analytical determination of yttrium, barium and copper in an YBa 2 Cu 3 O x superconductor is described. After dissolution of the material the concentration of Y and Cu was spectrophotometrically determined as an Y-Arsenazo III and a Cu-Nitroso-R-salt complex, respectively. Ba was determined either gravimetrically as BaCrO 4 , after precipitation using a K 2 CrO 4 solution or using flame atomic absorption spectroscopy (AAS). An accuracy better than 0.7% and a coefficient of variation better then 1.2% are obtained. It is illustrated that this analytical procedure can be used to determine the composition of a bulk superconducting YBa 2 Cu 3 O x sample. For determination of Ba in thin films we suggest the use of flame AAS, with an accuracy of 0.03% and a coefficient of variation of 1.7%

  18. Nanostructural characterization of artificial pinning centers in PLD-processed REBa{sub 2}Cu{sub 3}O{sub 7-δ} films

    Energy Technology Data Exchange (ETDEWEB)

    Maeda, T. [Department of Materials Science and Engineering, Kyushu University, 744, Motooka, Nishi, Fukuoka 819-0395 (Japan); Kaneko, K., E-mail: kaneko@zaiko.kyushu-u.ac.jp [Department of Materials Science and Engineering, Kyushu University, 744, Motooka, Nishi, Fukuoka 819-0395 (Japan); Yamada, K.; Roy, A.; Sato, Y.; Teranishi, R. [Department of Materials Science and Engineering, Kyushu University, 744, Motooka, Nishi, Fukuoka 819-0395 (Japan); Kato, T. [Japan Fine Ceramics Center, 2-4-1, Mutsuno, Atsuta, Nagoya 456-8587 (Japan); Izumi, T. [Research Institute for Energy Conservation, Department of Energy and Environment, National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba East, 1-2-1 Namiki, Tsukuba, Ibaraki 305-8564 (Japan); Shiohara, Y. [Industrial Superconductivity Technology Research Association, KSP R& D Wing A-9F, 3-2-1 Sakado, Takatsu, Kawasaki, Kanagawa 213-0012 (Japan)

    2017-05-15

    In the context of high temperature superconductors, pulsed laser deposition derived GdBa{sub 2}Cu{sub 3}O{sub 7-δ} sample with BaHfO{sub 3} nanoparticles has been reported to achieve high current density and good I{sub C}-B-θ characteristics at high temperatures. Herein, we have carried out a thorough nanostrucural characterization of BaHfO{sub 3} nanoparticles embedded in GdBCO matrix using scanning transmission electron microscopy, with an emphasis on the dispersion behavior, morphologies and nanostrain, to understand the role of BaHfO{sub 3} nanoparticles. - Highlights: • There were two distinct regions available of the way nanoparticles being dispersed within the matrix. • Tilted nanoparticle were found inclined slightly towards opposite direction. • The morphological studies suggested that they were slightly distorted octagonal prism. • Local strains were present at the interface between small BHO nanorod and GdBCO matrix. • The amount of the local strain in the matrix was decreased gradually from the interface.

  19. Method of depositing thin films of high temperature Bi-Sr-Ca-Cu-O-based ceramic oxide superconductors

    International Nuclear Information System (INIS)

    Budd, K.D.

    1991-01-01

    This patent describes a method. It comprises preparing a liquid precursor of a Bi-Sr-Ca-Cu-O- based ceramic oxide superconductor phase, wherein the liquid precursor comprises an alkoxyalkanol, copper acrylate, strontium acrylate, bismuth nitrate, and calcium nitrate, wherein the liquid precursor has a cation ratio sufficient to form the desired stoichiometry in the ceramic oxide superconductor phase when the liquid precursor is heated to a temperature and for a time sufficient to provide the desired ceramic oxide superconductor phase, and wherein the copper acrylate, strontium acrylate, bismuth nitrate, and calcium nitrate are mutually soluble in the alkoxyalkanol; applying the liquid precursor to a substrate, wherein the substrate is one of an oxide ceramic, a metal selected from the group consisting of Ag and Ni, and Si; and heating the substrate in an oxygen-containing atmosphere with the liquid precursor applied thereon to a temperature and for a time sufficient to form a thin film comprising at least one Bi-Sr- Ca-Cu-O-based high temperature ceramic oxide superconductor phase

  20. Accurate determination of the composition of Y-Ba-Cu-O superconductor by spectrophotometry, gravimetry and flame AAS

    Energy Technology Data Exchange (ETDEWEB)

    Bruneel, E [Department of Inorganic and Physical Chemistry, Ghent University, Krijgslaan 281(S3), 9000 Ghent (Belgium); Verbauwhede, D [Department of Inorganic and Physical Chemistry, Ghent University, Krijgslaan 281(S3), 9000 Ghent (Belgium); Vyver, D Van de [Department of Inorganic and Physical Chemistry, Ghent University, Krijgslaan 281(S3), 9000 Ghent (Belgium); Schaubroeck, J [Departement Industriele Wetenschappen, Hogeschool Gent, Schoonmeerstraat 52 9000 Ghent (Belgium); Hoste, S [Department of Inorganic and Physical Chemistry, Ghent University, Krijgslaan 281(S3), 9000 Ghent (Belgium); Driessche, I Van [Department of Inorganic and Physical Chemistry, Ghent University, Krijgslaan 281(S3), 9000 Ghent (Belgium)

    2005-06-01

    A procedure for the accurate analytical determination of yttrium, barium and copper in an YBa{sub 2}Cu{sub 3}O{sub x} superconductor is described. After dissolution of the material the concentration of Y and Cu was spectrophotometrically determined as an Y-Arsenazo III and a Cu-Nitroso-R-salt complex, respectively. Ba was determined either gravimetrically as BaCrO{sub 4}, after precipitation using a K{sub 2}CrO{sub 4} solution or using flame atomic absorption spectroscopy (AAS). An accuracy better than 0.7% and a coefficient of variation better then 1.2% are obtained. It is illustrated that this analytical procedure can be used to determine the composition of a bulk superconducting YBa{sub 2}Cu{sub 3}O{sub x} sample. For determination of Ba in thin films we suggest the use of flame AAS, with an accuracy of 0.03% and a coefficient of variation of 1.7%.

  1. Thickness-dependent radiative properties of Y-Ba-Cu-O thin films

    International Nuclear Information System (INIS)

    Phelan, P.E.; Chen, G.; Tien, C.L.

    1991-01-01

    Some applications of high-temperature superconductors where their thermal radiative behavior is important, such as bolometers, optically-triggered switches and gates, and space-cooled electronics, required the superconductor to be in the form of a very thin film whose radiative behavior cannot be adequately represented by a semi-infinite analysis. Two properties of particular importance are the film absorptance and the combined film/substrate absorptance, which are crucial to the operation of many devices. This paper reports on calculations of the absorptance of superconducting-state Y-Ba-Cu-O films on MgO substrates which suggest that for film thicknesses less than about 50 nm, a decrease in the film thickness leads to an increase in both the film absorptance and the film/substrate absorptance. Furthermore, the film absorptance is maximum at some optimal value of film thickness. Assuming the film to be a smooth, continuous slab with a refractive index equal to that of the bulk Y-Ba-Cu-O is verified, at least in the normal state and for films as thin as 35 nm, by room-temperature reflectance and transmittance measurements

  2. Anisotropy of the irreversibility field for Zr-doped $(Y,Gd)Ba_2Cu_3O_{7-x}$ thin films up to 45T

    OpenAIRE

    Tarantini, C.; Jaroszynski, J.; Kametani, F.; Zuev, Y. L.; Gurevich, A.; Chen, Y.; Selvamanickam, V.; Larbalestier, D. C.; Christen, D. K.

    2012-01-01

    The anisotropic irreversibility field B$_{Irr}$ of two $YBa_2Cu_3O_{7-x}$ thin films doped with additional rare earth (RE)=(Gd,Y) and Zr and containing strong correlated pins (splayed BaZrO$_{3}$ nanorods, and $RE_2O_3$ nanoprecipitates), has been measured over a very broad range up to 45T at temperatures 56 K

  3. Intermediate phases in the formation of the Cu-Ba-Y high-Tc superconductor from xerogel

    International Nuclear Information System (INIS)

    Arcon, I.; Bele, M.; Hribar, M.; Kodre, A.; Stuhec, M.; Pejovnik, S.; Frahm, R.

    1995-01-01

    In the synthesis of YBa 2 Cu 3 O 7-x superconductor ceramics by the sol-gel method, yttrium K EXAFS spectra of the intermediate products give evidence of the dynamics of the Y ion in the reaction. Together with previous data on Cu K and Ba L 3 EXAFS, the results give information on the processes in the amorphous phase, complementing the diffraction data on crystallite growth. ((orig.))

  4. Critical currents and thermally activated flux motion in high-temperature superconductors

    NARCIS (Netherlands)

    Palstra, T.T.M.; Batlogg, B.; Dover, R.B. van; Schneemeyer, L.F.; Waszczak, J.V.

    1989-01-01

    We have measured the resistance below Tc of single crystals of the high-temperature superconductors Ba2YCu3O7 and Bi2.2Sr2Ca0.8Cu2O8+δ in magnetic fields up to 12 T. The resistive transition of both compounds is dominated by intrinsic dissipation which is thermally activated, resulting in an

  5. Epataxial growth of the high-temperature superconductors YBa2Cu3O7-x on silicon single crystals with buffer layers

    International Nuclear Information System (INIS)

    Lubig, A.

    1991-09-01

    In this work the growth of thin films of the high-temperature superconductor YBa 2 Cu 3 O 7-x on Si(001) substrates has been investigated by Rutherford backscattering, channeling, X-ray diffraction, high resolution transmission electron microscopy, and electrical measurements. Epitaxial buffer layers of electrically insulating, pure and yttria-stabilized ZrO 2 ([Y 2 O 3 ] 0.06 [ZrO 2 ] 0.94 = YSZ) as well as of metallic CoSi 2 were employed to largely prevent the interdiffusion and chemical reaction between the superconductor film and the substrate in spite of the high deposition temperatures of the YBa 2 Cu 3 O 7-x in the range of 600 to 800deg C. (orig.)

  6. The improvement of the superconducting Y-Ba-Cu-O magnet characteristics through shape recovery strain of Fe-Mn-Si alloys

    International Nuclear Information System (INIS)

    Shimpo, Y.; Seki, H.; Wongsatanawarid, A.; Taniguchi, S.; Maruyama, T.; Kurita, T.; Murakami, M.

    2010-01-01

    Since bulk Y-Ba-Cu-O superconductors are brittle ceramics, reinforcement of mechanical properties is important for practical applications. It has been reported that bulk Y-Ba-Cu-O can be reinforced with Al or Fe based alloy ring, in that compression force acts on bulk Y-Ba-Cu-O due to a difference in thermal expansion coefficients. However, the shrinkage of the metal ring was not so large, and therefore careful adjustment of the circumference of the bulk and the metal rings was necessary. In this study, we employed Fe-Mn-Si shape memory alloy rings to reinforce bulk Y-Ba-Cu-O. The advantage of the shape memory alloy is that the shrinkage can take place on heating, and furthermore, the alloy shrinks and compresses the bulk body on cooling. Bulk Y-Ba-Cu-O superconductor 22.8 mm in diameter was inserted in a Fe-Mn-Si ring 23.0 mm in inner diameter at room temperature. Beforehand, the Fe-Mn-Si ring was expanded by 12% strain at room temperature. Then the composite was heated to 673 K. At room temperature, the Fe-Mn-Si ring firmly gripped the bulk superconductor. We then measured trapped fields before and after the ring reinforcement, and found that the trapped field was improved through the treatment.

  7. Magnetic tri-axial orientation in (Y1-xErx)2Ba4Cu7O15-y superconductors

    International Nuclear Information System (INIS)

    Horii, S.; Okuhira, S.; Yamaki, M.; Haruta, M.; Maeda, T.; Shimoyama, J.

    2011-01-01

    (Y 1-x Er x ) 2 Ba 4 Cu 7 O 15-y [(Y,Er)247] was synthesized for clarifying a magnetic role of Er ion. The three magnetization axes of (Y,Er)247 were obtained from tri-axial orientation using a modulated rotation magnetic field. Magnetic anisotropy of Er ion is roughly ten times higher than that for Y247 at room temperature. Importance of rare-earth ions was shown for reduction of required magnetic fields in the tri-axial magnetic orientation. We report the tri-axial grain-orientation effects under a modulated rotation magnetic field for (Y 1-x Er x ) 2 Ba 4 Cu 7 O y [(Y, Er)247]. The magnetic easy axis at room temperature was drastically changed around x ∼ 0.1; however, the Er-doping levels for the conversion of magnetic easy axes from the c-axis to the ab-direction and from the a- to b-axes were quite different. Tri-axial single-ion magnetic anisotropy of Er 3+ was roughly 10 times greater than tri-axial magnetic anisotropy generated by both the superconducting CuO 2 plane and the blocking Cu-O chain layer. An appropriate choice of rare-earth (RE) ions in RE-based cuprate superconductors enables the reduction of the required magnetic field for the production of bulks and thick films based on the magnetic orientation technique.

  8. Field-induced interplanar magnetic correlations in the high-temperature superconductor La1.88Sr0.12CuO4

    DEFF Research Database (Denmark)

    Rømer, A. T.; Jensen, P.; Jacobsen, H.

    2015-01-01

    We present neutron-scattering studies of the interplanar magnetic correlations in the high-temperature superconductor La1.88Sr0.12CuO4 (Tc=27 K). The correlations are studied both in a magnetic field applied perpendicular to the CuO2 planes, and in zero field under different cooling conditions. We...

  9. A superconducting conveyer system using multiple bulk Y-Ba-Cu-O superconductors and permanent magnets

    Science.gov (United States)

    Kinoshita, T.; Koshizuka, N.; Nagashima, K.; Murakami, M.

    Developments of non-contact superconducting devices like superconducting magnetic levitation transfer and superconducting flywheel energy storage system have been performed based on the interactions between bulk Y-Ba-Cu-O superconductors and permanent magnets, in that the superconductors can stably be levitated without any active control. The performances of noncontact superconducting devices are dependent on the interaction forces like attractive forces and stiffness. In the present study, we constructed a non-contact conveyer for which the guide rails were prepared by attaching many Fe-Nd-B magnets onto an iron base plate. Along the translational direction, all the magnets were arranged as to face the same pole, and furthermore their inter-distance was made as small as possible. The guide rail has three magnet rows, for which the magnets were glued on the iron plate such that adjacent magnet rows have opposite poles like NSN. At the center row, the magnetic field at zero gap reached 0.61T, while the field strengths of two rows on the side edges were only 0.48T due to magnetic interactions among permanent magnets. We then prepared a cryogenic box made with FRP that can store several bulk Y-Ba-Cu-O superconductors 25 mm in diameter cooled by liquid nitrogen. It was found that the levitation forces and stiffness increased with increasing the number of bulk superconductors installed in the box, although the levitation force per unit bulk were almost the same. We also confirmed that these forces are dependent on the configuration of bulk superconductors.

  10. The Effect of Oxygen Flow on the Transition Temperature of Hg0.75Pb0.25Sr2-yBayCa2Cu3O8+ δ Superconductors

    Science.gov (United States)

    Jasim, Kareem A.; Al-Khafaji, Raghad S.

    2018-05-01

    In this paper, there are three different high temperature superconductors which are Hg0.75Pb0.25Sr2-y BayCa2Cu3O8+δ with deferent weight fractions y = 0.10, 0.20 and 0.25 that have been prepared successfully by solid state reaction and the samples have been equipped with/without O2 flow. The optimum calcinations is 1073 K and the sintering process that has been achieved within 1128-1133 K. Transition temperature Tc has been found by using four probe technique through electrical resistivity measurements. The greatest Tc that has been found for Hg0.75Pb0.25Sr1.75 Ba0.25Ca2Cu3O8.31 is 115 oK. Oxygen content (O2) flow exhibits high-phased superconductors that is similar to the samples prepared without O2. Investigation of X-ray diffraction (XRD) is revealed (tetragonal structure) by the c-axis lattice parameter increasing of the samples substituted with Ba. It has been established, from the calculated results, that the Ba variation concentrations of all samples products a modification in the density (ρm), (c/a) and volume fraction (VPh(2223)).

  11. Trapped magnetic field of a superconducting bulk magnet in high- T sub c RE-Ba-Cu-O

    CERN Document Server

    Fujimoto, H; Higuchi, T; Nakamura, Y; Kamijo, H; Nagashima, K; Murakami, M

    1999-01-01

    Superconducting magnets made of high-T sub c superconductors are promising for industrial applications. It is well known that REBa sub 2 Cu sub 3 O sub 7 sub - sub x and LRE (light rare-earth) Ba sub 2 Cu sub 3 O sub 7 sub - sub x superconductors prepared by melt processes have a high critical current density, J sub c , at 77 K and high magnetic fields. Therefore, the materials are very prospective for high magnetic field application as a superconducting permanent/bulk magnet with liquid-nitrogen refrigeration. LREBaCuO bulks, compared with REBaCuO bulks, exhibit a larger J sub c in high magnetic fields and a much improved irreversibility field, H sub i sub r sub r , at 77 K. In this study, we discuss the possibility and trapped field properties of a superconducting bulk magnet, as well as the melt processing for bulk superconductors and their characteristic superconducting properties. One of the applications is a superconducting magnet for the future magnetically levitated (Maglev) train.

  12. Oxide glass to high temperature ceramic superconductors - a novel route

    International Nuclear Information System (INIS)

    Chaudhuri, B.K.; Som, K.K.

    1992-01-01

    Recently it has been discovered that many of transition metal oxide (TMO) glasses like Bi-Sr-Ca-Cu-O, Y-Ba-Cu-O, Bi-Pb-Sr-Ca-Cu-O etc. can be directly converted to the corresponding high temperature superconducting phases by properly annealing the respective glasses. In this review recent developements in this field are summarised. The structural, electrical, dielectrical, magnetic, optical, and other properties of these new type of (TMO) glass systems have been elucidated comparing them with the corresponding results of already known (TMO) glasses which do not become superconductors on annealing above their glass transition temperatures (T g ). The electrical properties of this novel glass system have been analysed with reference to the various existing theoretical models based on polaron hopping conduction mechanism. The electrical, magnetic, and other properties of the respective superconductors obtained from their corresponding glass phases by annealing above (T g ) and the possibility of drawing wires, ribbons etc. from these glass matrices and then converting them to their high T c superconducting phases have also been discussed. (author). 107 refs., 32 figs., 5 tabs

  13. Studies of superconductors using a low-temperature, high-field scanning tunneling microscope

    International Nuclear Information System (INIS)

    Kirtley, J.R.; Feenstra, R.M.; Fein, A.P.

    1988-01-01

    We have developed a scanning tunneling microscope (STM) capable of operating at temperatures as low as 0.4 K and fields as high as 8 T. We have used this STM to study the energy gap of the high-T/sub c/ superconductors La--Sr--Cu--O and Y--Ba--Cu--O. We find that the reduced gap for these oxide superconductors falls in the range 3<2Δ/k/sub B/T/sub c/<7, for polycrystalline, single-crystal, and thin-film samples. We have also simultaneously imaged the surface topography and superconducting energy gap for thin films of the granular superconductor NbN. We occasionally see regions with smaller best-fit gaps that correlate with surface topographical features, but have been unable so far to image flux vortices

  14. Electronic structure of the gold/Bi2Sr2CaCu2O8 and gold/EuBa2Cu3O7-δ interfaces as studied by photoemission spectroscopy

    International Nuclear Information System (INIS)

    Dessau, D.S.; Shen, Z.; Wells, B.O.; Spicer, W.E.; List, R.S.; Arko, A.J.; Bartlett, R.J.; Fisk, Z.; Cheong, S.; Mitzi, D.B.; Kapitulnik, A.; Schirber, J.E.

    1990-01-01

    High-resolution photoemission has been used to probe the electronic structure of the gold/Bi 2 Sr 2 CaCu 2 O 8 and gold/EuBa 2 Cu 3 O 7-δ interface formed by a low-temperature (20 K) gold evaporation on cleaved high quality single crystals. We find that the metallicity of the EuBa 2 Cu 3 O 7-δ substrate in the near surface region (∼5 A) is essentially destroyed by the gold deposition, while the near surface region of Bi 2 Sr 2 CaCu 2 O 8 remains metallic. This has potentially wide ranging consequences for the applicability of the different types of superconductors in real devices

  15. Superconducting properties of GdBa{sub 2}Cu{sub 3}O{sub y} films by metal-organic deposition using new fluorine-free complex solutions

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, T. [Department of Electrical and Electronic Engineering, Faculty of Engineering, Shizuoka University, Johoku 3-5-1, Hamamatsu, Shizuoka 432-8561 (Japan); Kita, R. [Department of Electrical and Electronic Engineering, Faculty of Engineering, Shizuoka University, Johoku 3-5-1, Hamamatsu, Shizuoka 432-8561 (Japan); CREST-JST, Honcho 4-1-8, Kawaguchi, Saitama 332-0012 (Japan)], E-mail: terkita@ipc.shizuoka.ac.jp; Miura, O. [Tokyo Metropolitan University, Minamiosawa 1-1, Hachioji, Tokyo 192-0364 (Japan); CREST-JST, Honcho 4-1-8, Kawaguchi, Saitama 332-0012 (Japan); Ichinose, A. [CRIEPI, Nagasaka 2-6-1, Yokosuka, Kanagawa 240-0916 (Japan); CREST-JST, Honcho 4-1-8, Kawaguchi, Saitama 332-0012 (Japan); Matsumoto, K. [Kyushu Institute of Techonology, Sensui-cho, Tobata-ku, Kitakyushu, Hukuoka 804-8550 (Japan); CREST-JST, Honcho 4-1-8, Kawaguchi, Saitama 332-0012 (Japan); Yoshida, Y. [Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); CREST-JST, Honcho 4-1-8, Kawaguchi, Saitama 332-0012 (Japan); Mukaida, M. [Kyushu University, Hakozaki 6-10-1, Higashi-ku 4-3-16, Fukuoka 992-8510 (Japan); CREST-JST, Honcho 4-1-8, Kawaguchi, Saitama 332-0012 (Japan); Horii, S. [University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8586 (Japan); CREST-JST, Honcho 4-1-8, Kawaguchi, Saitama 332-0012 (Japan)

    2008-09-15

    GdBa{sub 2}Cu{sub 3}O{sub y} (GdBCO) films have been prepared on LaAlO{sub 3} single-crystal substrates by metal-organic deposition (MOD) using new fluorine-free complex solutions consisting of metal 2-ethylhexanates (2-EH) and metal naphthenates. The dispersion of T{sub c} values for GdBCO films improved by using a complex solution, rather than only a solution of metal naphthenates. c-axis oriented GdBCO films with flat surfaces were grown under lower calcining temperatures and higher firing temperatures than in the process using only metal naphthenates. The T{sub c} and J{sub c} of the GdBCO films were 91.2 K and 0.61 MA/cm{sup 2}, respectively, at 77 K at self-field.

  16. Influence of Y2BaCuO5 precipitates on the current density of melt processed YBa2Cu3Ox superconductor

    International Nuclear Information System (INIS)

    Salama, K.; Selvamanickam, V.

    1992-01-01

    YBa 2 Cu 3 O x superconductors fabricated by melt processing methods have been shown to exhibit current density around 10 5 A/cm 2 at 77 K. Since YBa 2 Cu 3 O x decomposes peritectically above 1000 C, more than 50 vol. % of Y 2 BaCuO 5 (211) precipitates are formed during the incongruent melting. Even under stringent slow cooling conditions, a significant amount of these precipitates remain unreacted with the liquid and are left embedded in the long 123 grains. The potential of these precipitates as flux pinning sites has been investigated extensively, but remains controversial. In this study, we have performed transport current density measurements on melt processed YBa 2 Cu 3 O x superconductor prepared with varying amount of 211 precipitates. The current density measurements were performed in magnetic fields up to 1.5 T at 77 K with the field aligned at different angles to the a-b plane. The results provided in this paper show that Jc decreases monotonically with increasing amount of 211, irrespective of the angle between the field and the a-b plane indicating the absence of significant pinning by 211 precipitates in melt processed YBa 2 Cu 3 O x superconductor

  17. Electron paramagnetic resonance and AC susceptibility studies of Mn and Gd doped 1:2:3 superconductors

    International Nuclear Information System (INIS)

    La Robina, M.A.

    1997-01-01

    For many years superconductivity was considered to be a low temperature phenomenon occurring below ∼ 25K. All this changed in April 1986 when J. G. Bednorz and K. A. Muller showed that the oxide La 2-x Ba x CuO 4 becomes a superconductor at ∼ 30K. Later in December 1986 the oxides La 2-x Sr x CuO 4 and La 2-x Ba x CuO 4 synthesised under high pressure, were shown to superconduct at ∼ 40K and ∼ 50K, respectively. Finally in February 1987, Chu synthesised the classic superconductor YBa 2 Cu 3 O 6.8 , the so-called 1:2:3 material, which has a critical temperature circa 92K. In this thesis, electron paramagnetic resonance (EPR) and susceptibility measurements are reported on various superconductors. In 1987 Bowden et al., showed that pure phase 1:2:3 samples are characterised by an absence of Cu EPR signals. This contrasts sharply with the Green phase material, Y 2 Ba 1 Cu 1 O 5 , which shows a very large EPR signal with a g eff of 2.08. In an attempt to induce EPR signals, Mn doped 1:2:3 samples have been synthesised and characterised with EPR , AC susceptibility, XRD and SEM measurements. It is shown that Mn EPR signals are not evident in the Mn doped samples with a g eff of 2.09. Also, below T c the EPR signals of the lightly doped Mn samples vanish. It is argued that this is due to fluxoids motion within the superconductor, which gives rise to very large non-reproducible signals. It is suggested that the signals originate from Cu, impurity contaminants and multiple phases produced when the 1:2:3 superconductor is doped with Manganese (author)

  18. The effect of nano-size ZrO2 powder addition on the microstructure and superconducting properties of single-domain Y-Ba-Cu-O bulk superconductors

    International Nuclear Information System (INIS)

    Iida, K; Babu, N H; Reddy, E S; Shi, Y-H; Cardwell, D A

    2005-01-01

    The effect of nano-size ZrO 2 powder addition on the microstructure and superconducting properties of Y-Ba-Cu-O single grain bulk superconductors has been investigated. Significant pushing phenomena of Y 2 BaCuO 5 (Y-211) particles, particularly in the c growth sector, were observed even with a small amount of ZrO 2 added to the precursor powder. An increase in Y-211 particle pushing was observed with increasing ZrO 2 content, leading to an inhomogeneous bulk microstructure. In addition, a growth cycle consisting of a Y-211 free layer-porous narrow layer-Y-211 high concentration layer was observed for samples prepared with 0.25 wt% ZrO 2 in both the a and c growth sectors. The extent of the growth of single grain Y-Ba-Cu-O (YBCO) decreased with increasing ZrO 2 content due to increased pushing of Y-211 particles towards molten liquid. The superconducting transition temperature, T c , of the ZrO 2 containing YBCO samples was sharp but depressed slightly (by up to 1 K) compared with an undoped YBCO grain, indicating a relative insensitivity of T c to ZrO 2 content. Finally, the sensitivity of critical current density, J c , to applied magnetic field in large grain bulk YBCO containing ZrO 2 was observed to depend critically on position due to the inhomogeneous sample microstructure

  19. Preparation and characterization of Y-Ba-Cu-O-F superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Yokoyama, Yuko; Okumura, Tomoyuki; Sugise, Ryoji; Matsubara, Toshiya; Koshizuka, Naoki; Hirabayashi, Masayuki; Terada, Norio; Ihara, Hideo

    1988-04-01

    Samples were prepared by powder composition method which uses fluoride for annealing and by the method which anneals YBa/sub 2/Cu/sub 3/O/sub x/ in fluorine to elucidate fluorine substitution effects on the superconducting properties of YBa/sub 2/Cu/sub 3/O/sub/x/F/sub/y/. Their structures, magnetic properties and electrical conductivities were investigated. The samples were prepared with the appropriate mixture of BaCO/sub 3/, Y/sub 2/O/sub 3/, CuO, and fluoride such as CuF/sub 2/. Since the samples had strong peaks of BaF/sub 2/ phase together with the perovskite phase in the X-ray diffraction patterns, it was difficult to obtain information on the fluorine substitution effects on the physical properties. Next, the samples were prepared by annealing YBa/sub 2/CuO/sub/x/ sintred pellets and CoF/sub 3/ powder in a sealed quartz tube. In this case, the diffraction patterns showed that the crystalline state of the samples was a single phase of the orthorohombic perovskite structure. The behaviors against the changes in magnetic field and temperature can be considered to be substantially identical. It is hard to consider that the fluorine substitution will play a direct role in attaining higher Tc. (6 figs, 2 refs)

  20. Paramagnetism and magnetic relaxation in melt-textured grown GdBa2Cu3O6+y

    International Nuclear Information System (INIS)

    Qin, M.J.; Fu, X.K.; Ren, H.T.

    1996-01-01

    Magnetic measurements have been performed on a melt-textured grown (MTG) GdBa 2 Cu 3 O 6+y sample. Because of the paramagnetism of the Gd 3+ ions, the magnetization relaxation rate is increased by a factor of 4πχ. The effect of paramagnetism on the U(J) relationship of the sample has also been discussed. At the end, we extraxted the U(J) relationship based on the field sweep rate H, which is in agreement with the one after corrections for paramagnetism. (orig.)

  1. Formation of YxNd1-xBa2Cu3O7-δ (0≤x≤0.9) superconductors from an undercooled melt via aero-acoustic levitation

    International Nuclear Information System (INIS)

    Gustafson, D.E.; Hofmeister, W.H.; Bayuzick, R.J.; Nagashio, K.; Kuribayashi, K.

    2003-01-01

    This paper presents the results of rapid solidification experiments performed on the copper oxide superconductors Y x Nd 1-x Ba 2 Cu 3 O 7-δ (0≤x≤0.9). Spherical rare earth (RE) 123 specimens were levitated in O 2 using aero-acoustic levitation (AAL), melted with a laser, undercooled, and solidified. The peritectic transformation temperature for the reaction RE 2 BaCuO 5 +liquid→REBa 2 Cu 3 O 7-δ corresponding to the maximum recalescence temperature during solidification was determined. RE123 was formed directly from the melt for Y-Nd binary alloy compositions with Nd concentration greater than 20% (Y concentration less than 80%). A minimum in the peritectic transformation temperature for the Nd/Y123 system corresponding to a composition Y 0.3 Nd 0.7 123 was determined at 66 deg. C below the peritectic of pure Nd123

  2. μSR investigations of the high temperature superconductors La1.85Sr0.15CuO4 and YBa2Cu3O7-δ

    International Nuclear Information System (INIS)

    Birrer, P.; Gygax, F.N.; Hitti, B.

    1987-01-01

    μSR studies of La 1.85 Sr 0.15 CuO 4 and YBa 2 Cu 3 O 7-δ high temperature superconductors are carried out. The interval magnetic properties of these systems are studied on a microscopic level in the 4 kOe magnetic field and in the temperature range 10 K - 120 K. The magnetic penetration depth λ in this system did not show any significant differences from the two temperature scans (10 K and 120 K) and it destroys a field independence above 1 kOe. For T=OK the authers obtain λ(OK)≅2650 A

  3. Behavior of the irreversibility line in the new superconductor La{sub 1.5+x}Ba{sub 1.5+x-y}Ca{sub y}Cu{sub 3}O{sub z}

    Energy Technology Data Exchange (ETDEWEB)

    Parra Vargas, C.A. [Grupo de Fisica de Materiales, Escuela de Fisica, Universidad Pedagogica y Tecnologica de Colombia, Tunja (Colombia); Pimentel, J.L.; Pureur, P. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, 91501-970 Porto Alegre, RS (Brazil); Landinez Tellez, D.A. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 5997, Bogota DC (Colombia); Roa-Rojas, J., E-mail: carlos.parra@uptc.edu.co [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 5997, Bogota DC (Colombia)

    2012-08-15

    The irreversibility properties of high-T{sub c} superconductors are of major importance for technological applications. For example, a high irreversibility magnetic field is a more desirable quality for a superconductor . The irreversibility line in the H-T plane is constituted by experimental points, which divides the irreversible and reversible behavior of the magnetization. The irreversibility lines for series of La{sub 1.5+x}Ba{sub 1.5+x-y}Ca{sub y}Cu{sub 3}O{sub z} polycrystalline samples with different doping were investigated. The samples were synthesized using the usual solid estate reaction method. Rietveld-type refinement of x-ray diffraction patterns permitted to determine the crystallization of material in a tetragonal structure. Curves of magnetization ZFC-FC for the system La{sub 1.5+x}Ba{sub 1.5+x-y}Ca{sub y}Cu{sub 3}O{sub z}, were measured in magnetic fields of the 10-20,000 Oe, and allowed to obtain the values for the irreversibility and critical temperatures. The data of irreversibility temperature allowed demarcating the irreversibility line, T{sub irr}(H). Two main lines are used for the interpretation of the irreversibility line: one of those which suppose that the vortexes are activated thermally and the other proposes that associated to T{sub irr} a phase transition occurs. The irreversibility line is described by a power law. The obtained results allow concluding that in the system La{sub 1.5+x}Ba{sub 1.5+x-y}Ca{sub y}Cu{sub 3}O{sub z} a characteristic bend of the Almeida-Thouless (AT) tendency is dominant for low fields and a bend Gabay-Toulouse (GT) behavior for high magnetic fields. This feature of the irreversibility line has been reported as a characteristic of granular superconductors and it corroborates the topological effects of vortexes mentioned by several authors .

  4. Investigation of (Y,Gd)Ba2Cu3O7-x grown by MOCVD on a simplified IBAD MgO template

    International Nuclear Information System (INIS)

    Stan, L; Holesinger, T G; Maiorov, B; Civale, L; DePaula, R F; Jia, Q X; Chen, Y; Xiong, X; Selvamanickam, V

    2010-01-01

    We have used an ion beam sputtered Y 2 O 3 -Al 2 O 3 (YALO) composite to simplify the architecture of high temperature superconducting (HTS) coated conductors (CCs) based on a IBAD MgO template. By implementing YALO, we have reduced the total non-superconducting layers between the polycrystalline metal substrate and the superconducting film from five (the standard architecture) to four. Well textured (Y,Gd)Ba 2 Cu 3 O 7-x ((Y, Gd)BCO) films have been successfully grown by MOCVD on this simplified template. The microstructural characterization revealed that all layers are continuous and uniform with sharp and clean interfaces. Additionally, the YALO maintained its amorphous nature after the deposition of the superconductive layer, which is a plus in terms of its efficiency as a diffusion barrier. The achievement of a self-field critical current of 230 A cm -1 at 75.5 K is another proof of the effectiveness of YALO as a diffusion barrier and nucleation seed for the MgO. The transport properties under an applied magnetic field of MOCVD grown (Y, Gd)BCO on LMO buffered MgO/YALO/Ni-alloy are comparable with those of (Y, Gd)BCO on a standard architecture, thus demonstrating good compatibility between the simplified template with the MOCVD grown (Y, Gd)BCO. The use of a single composite YALO layer instead of individual layers of Y 2 O 3 and Al 2 O 3 for the large scale fabrication of HTS CCs based on IBAD MgO provides advantages such as potentially reduced cost due to the reduced number of fabrication steps.

  5. Microstructural analyses and critical current densities in the high-Tc superconductor system ReBa2Cu3OX, with RE = Y, Sm, Eu, Gd, Dy, Ho

    International Nuclear Information System (INIS)

    Schindler, G.; Seebacher, B.

    1989-01-01

    The authors report on investigations into the impact of the rare earths (RE) as given in the title on the ceramic microstructure and the critical current density j c in the superconductor system REBa 2 Cu 3 O x . With RE = Sm, Eu, or Gd, the material is homogeneous in phase and crystallizes in platelets with maximum sizes of up to 350 μm. Material with RE = Y, Dy, or Ho exhibits grain sizes up to 500 μm, and a low amount of phase inhomogeneities. The critical currents measured are between 25 Acm -2 and 290 Acm -2 at 77 K, without external field. The highest values are found in systems with RE = Eu or Gd. (orig.) [de

  6. SmBa2NbO6 Nanopowders, an Effective Percolation Network Medium for YBCO Superconductors

    Directory of Open Access Journals (Sweden)

    S. Vidya

    2013-01-01

    Full Text Available The percolation behavior of superconductor-insulator composite, YBa2Cu3O7–δ, and nano SmBa2NbO2 synthesized by modified combustion technique was studied. Particle size of nano SmBa2NBO6 was determined using transmission electron microscopy. The chemical nonreactivity of nano SmBa2NbO6 with YBCO is evident from the X-Ray diffraction study which makes it a suitable nanoceramic substrate material for high temperature superconducting films. A systematic increase in the sintered density, approaching the optimum value of the insulating nanophase is clearly observed, as the vol.% of YBCO in the composite decreases. SEM micrograph showed uniform distribution of nanopowder among the large clusters of YBCO. The obtained percolation threshold is ~26 vol% of YBCO in the composite. All the composites below the threshold value showed TC(0~92 K even though the room resistivity increases with increase in vol.% of nano SmBa2NbO6. The values of critical exponents obtained matches well with the theoretically expected ones for an ideal superconductor-insulator system.

  7. Conductivity fluctuation in the high temperature superconductor with planar weight disparity Y0.5Sm0.5Ba2Cu3O7-δ

    International Nuclear Information System (INIS)

    Barrera, E.W.; Rojas Sarmiento, M.P.; Rincon, L.F.; Landinez Tellez, D.A.; Roa-Rojas, J.

    2007-01-01

    The synthesis of the Y 0.5 Sm 0.5 Ba 2 Cu 3 O 7-δ superconducting material by the standard solid state reaction is reported. DC resistivity measurements reveal the improvement of the critical temperature (T c ) when substitution of exact 50-50 mix of Yttrium and Samarium is performed. A bulk T c = 101 K was determined by the criterion of the maximum in the temperature derivative of electrical resistivity. Structure characterization by means the x-ray diffraction technique shows the crystalline appropriated distribution of Yttrium and Samarium to create substantial planar weight disparity (PWD) in alternating layers. This PWD increases T c in copper-oxide superconductors. In order to examine the effect of PWD on the pairing mechanism close to T c , conductivity fluctuation analysis was performed by the method of logarithmic temperature derivative of the conductivity excess. We found the occurrence of Gaussian and genuinely critical fluctuations. Our results are in agreement with reports on YBa 2 Cu 3 O 7-δ , but an enhancement of the Gaussian fluctuation regimes was experimentally detected as a result of the PWD. The correlations of the critical exponents with the dimensionality of the fluctuation system for each Gaussian regime were performed by using the Aslamazov-Larkin theory. The genuinely critical exponent is interpreted by the 3D-XY model as corresponding with the dynamical universality class of the E-model. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Low-temperature specific heat of single-crystal Bi2CaSr2Cu2O8 and Tl2Ca2Ba2Cu3O10

    Science.gov (United States)

    Urbach, J. S.; Mitzi, D. B.; Kapitulnik, A.; Wei, J. Y. T.; Morris, D. E.

    1989-06-01

    We report specific-heat measurements from 2 to 15 K on single crystals of Bi2CaSr2Cu2O8 and Tl2Ca2Ba2Cu3O10 We find low-temperature deviations from the Debye law that can be attributed to spin-glass behavior of a small concentration of isolated impurity copper moments. At higher temperatures, we observe contributions to the specific heat that can be attributed to a soft-phonon mode, possibly associated with the superstructure in the Bi-O and Tl-O layers. From our single-crystal data, we conclude that the thallium- and bismuth-based copper oxide superconductors show no measurable linear term in the specific heat [γ(0)<=1 mJ/mole K2].

  9. Grain alignment in bulk YBa2Cu3Ox superconductor by a low temperature phase transformation method

    International Nuclear Information System (INIS)

    Selvamanickam, V.; Goyal, A.; Kroeger, D.M.

    1994-01-01

    A quench and directional phase transformation process has been developed to achieve grain alignment in bulk YBa 2 Cu 3 O x superconductors at temperatures about 100 degree C below the peritectic temperature. Isothermal phase transformation of quenched precursors at 890 degree C for 3 min is found to result in the formation of more than 75% of YBa 2 Cu 3 O x phase without any formation of Y 2 BaCuO 5 . Phase transformation at higher temperatures leads to rapid formation of Y 2 BaCuO 5 in addition to YBa 2 Cu 3 O x . A well-aligned microstructure is achieved by directional phase transformation of the quenched compacts as a rate of 10 mm/h. The magnetic field dependence of the critical current density at 77 K of the directionally phase transformed material compares well with that of melt-textured YBCO and is superior to that of magnetically aligned and sintered YBCO

  10. Structural and superconducting properties of (Y,Gd)Ba2Cu3O7-δ grown by MOCVD on samarium zirconate buffered IBAD-MgO

    International Nuclear Information System (INIS)

    Stan, L; Holesinger, T G; Maiorov, B; Feldmann, D M; Usov, I O; DePaula, R F; Civale, L; Foltyn, S R; Jia, Q X; Chen, Y; Selvamanickam, V

    2008-01-01

    Textured samarium zirconate (SZO) films have been grown by reactive cosputtering directly on an ion beam assisted deposited (IBAD) MgO template, without an intermediate homoepitaxial MgO layer. The subsequent growth of 0.9 μm thick (Y,Gd)Ba 2 Cu 3 O 7-δ ((Y, Gd)BCO) films by metal organic chemical vapor deposition (MOCVD) yielded well textured films with a full width at half maximum of 1.9 0 and 3.4 0 for the out-of-plane and in-plane texture, respectively. Microstructural characterizations of the SZO buffered samples revealed clean interfaces. This indicates that the SZO not only provides a diffusion barrier, but also functions as a buffer for (Y, Gd)BCO grown by MOCVD. The achievement of self-field critical current densities (J c ) of over 2 MA cm -2 at 75.5 K is another proof of the effectiveness of SZO as a buffer on the IBAD-MgO template. The in-field measurements revealed an asymmetric angular dependence of J c and a shift of the ab-plane maxima due to the tilted nature of the template and (Y,Gd) 2 O 3 particles existing in the (Y, Gd)BCO matrix. The present results are especially important because they demonstrate that high temperature superconducting coated conductors with simpler architecture can be fabricated using commercially viable processes

  11. Electronic structure of the Y Ba{sub 2} Cu{sub 3} O{sub 7-x} high temperature superconductor ceramic; Estrutura eletronica da ceramica supercondutora de alta temperatura Y Ba{sub 2} Cu{sub 3} O{sub 7-x}

    Energy Technology Data Exchange (ETDEWEB)

    Lima, G A.R. [UNESP, Guaratingueta, SP (Brazil). Faculdade de Engenharia. Dept. de Fisica e Quimica

    1991-12-31

    We investigate the electronic structure of superconductor Y Ba{sub 2} Cu{sub 3} O{sub 7-x} through a molecular cluster approach. The calculations are performed self consistently through a semi empirical L.C.A.O. technique, where different charge states are considered. The correlation effects are taken into account by configuration interaction procedure (INDO/CI). The results for the larger cluster yield a density of states showing a strong p-d covalency resulting in a width of around 8,0 eV for the valence band. The optical excitations is analyzed in detail and compared with the experimental data. (author) 18 refs., 2 figs., 1 tab.

  12. Effect of Zn on the structural and electrical properties of high temperature HgBa2Ca2Cu3O8+δ superconductor

    Science.gov (United States)

    Omar, Bilal A.; Fathi, Sabah J.; Jassim, Kareem A.

    2018-05-01

    Bulk polycrystalline HgBa2Ca2-yZnyCu3O8+δ compound samples with y =0.0, 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3, are synthesized by a solid state reaction process. Study identifies Zinc partial substitution on superconductivity behavior. Structural properties are studied by using X-ray powder pattern, the high temperature phase superconductor (Hg-1223) of the tetragonal structure didn't change with the partial substitution of Zn ions in Ca site, lattice parameters c, c/a are established to vary Zn-substitution. The surface morphology has been studied by using atomic force microscopes (AFM), showed that all specimens have good crystalline and homogeneous surface. Also give a best nano size value is 83.29 nm at y=0.05. Four probe technique is used to measure Tc. The highest Tc and oxygen content were found to be Tc=132 K for y=0.05 after that, Tc decreases from 132 K to 115 K with increasing Zn. In addition, dielectric properties (dielectric constant, dielectric loss factor, and the alternating electrical conductivity) are characterized directly by relating with Zn concentration.

  13. Theoretical study of cathode surfaces and high-temperature superconductors

    Science.gov (United States)

    Mueller, Wolfgang

    1995-01-01

    Calculations are presented for the work functions of BaO on W, Os, Pt, and alloys of Re-W, Os-W, and Ir-W that are in excellent agreement with experiment. The observed emission enhancement for alloy relative to tungsten dispenser cathodes is attributed to properties of the substrate crystal structure and explained by the smaller depolarization of the surface dipole on hexagonal as compared to cubic substrates. For Ba and BaO on W(100), the geometry of the adsorbates has been determined by a comparison of inverse photoemission spectra with calculated densities of unoccupied states based on the fully relativistic embedded cluster approach. Results are also discussed for models of scandate cathodes and the electronic structure of oxygen on W(100) at room and elevated temperatures. A detailed comparison is made for the surface electronic structure of the high-temperature superconductor YBa2Cu3O7 as obtained with non-, quasi-, and fully relativistic cluster calculations.

  14. Behavior of the irreversibility line in the new superconductor La1.5+xBa1.5+x-yCayCu3Oz

    International Nuclear Information System (INIS)

    Parra Vargas, C.A.; Pimentel, J.L.; Pureur, P.; Landínez Téllez, D.A.; Roa-Rojas, J.

    2012-01-01

    The irreversibility properties of high-T c superconductors are of major importance for technological applications. For example, a high irreversibility magnetic field is a more desirable quality for a superconductor . The irreversibility line in the H-T plane is constituted by experimental points, which divides the irreversible and reversible behavior of the magnetization. The irreversibility lines for series of La 1.5+x Ba 1.5+x-y Ca y Cu 3 O z polycrystalline samples with different doping were investigated. The samples were synthesized using the usual solid estate reaction method. Rietveld-type refinement of x-ray diffraction patterns permitted to determine the crystallization of material in a tetragonal structure. Curves of magnetization ZFC-FC for the system La 1.5+x Ba 1.5+x-y Ca y Cu 3 O z , were measured in magnetic fields of the 10-20,000 Oe, and allowed to obtain the values for the irreversibility and critical temperatures. The data of irreversibility temperature allowed demarcating the irreversibility line, T irr (H). Two main lines are used for the interpretation of the irreversibility line: one of those which suppose that the vortexes are activated thermally and the other proposes that associated to T irr a phase transition occurs. The irreversibility line is described by a power law. The obtained results allow concluding that in the system La 1.5+x Ba 1.5+x-y Ca y Cu 3 O z a characteristic bend of the Almeida-Thouless (AT) tendency is dominant for low fields and a bend Gabay-Toulouse (GT) behavior for high magnetic fields. This feature of the irreversibility line has been reported as a characteristic of granular superconductors and it corroborates the topological effects of vortexes mentioned by several authors .

  15. Mechanical properties of polycrystalline RuSr2GdCu2O8 superconductor

    International Nuclear Information System (INIS)

    Brum Leite Gusmao Pinheiro, Lincoln; Serbena, Francisco Carlos; Foerster, Carlos Eugenio; Rodrigues, Pedro Junior; Jurelo, Alcione Roberto; Chinelatto, Adilson Luiz; Junior, Jorge Luiz Pimentel

    2011-01-01

    Research highlights: → Hardness and elastic modulus of Ru-1212 phase measured by instrumented indentation are reported. → Polycrystalline samples were produced by a solid state reaction technique. → Samples were also characterized by SEM, XRD and electrical resistivity measurements. → Hardness and elastic modulus were 8.6 GPa and 145 GPa, respectively. → These values are comparable with those of Y-123. - Abstract: The main objective of this paper is to report the room temperature hardness and elastic modulus of the RuSr 2 GdCu 2 O 8 superconductor phase by instrumented indentation. Polycrystalline samples were produced by a solid state reaction technique. The samples were also characterized by scanning electron microscopy, X-ray diffraction and electrical resistivity measurements. The influence of porosity on the mechanical properties was avoided by considering only those indentations inside the grains. The hardness and elastic modulus were 8.6 GPa and 145 GPa, respectively. These values are comparable with those of Y-123. The indentation fracture toughness evaluated after conventional Vickers indentation was 1.9 MPa m 1/2 .

  16. Magnetic-Field-Enhanced Incommensurate Magnetic Order in the Underdoped High-Temperature Superconductor YBa2Cu3O6.45

    DEFF Research Database (Denmark)

    Haug, D.; Hinkov, V.; Suchaneck, A.

    2009-01-01

    We present a neutron-scattering study of the static and dynamic spin correlations in the underdoped high-temperature superconductor YBa2Cu3O6.45 in magnetic fields up to 15 T. The field strongly enhances static incommensurate magnetic order at low temperatures and induces a spectral-weight shift...

  17. Advanced technologies related to a high temperature superconductor for small laboratory experiments

    International Nuclear Information System (INIS)

    Ogawa, Yuichi; Mito, Toshiyuki; Yanagi, Nagato

    2006-01-01

    Advanced technologies related to a high temperature superconductor materials and small refrigerator are reviewed. Mini-RT/RT-1 is designed and constructed as a plasma examination device. The element technology of low temperature apparatus, the results of performance tests and application examples are explained. The superconductors such as Bi 2 Sr 2 CaCu 2 O 8 (Bi-2212) for the low temperature phase, Bi 2 Sr 2 Ca 2 Cu 3 O 10 (Bi-2223) for the high temperature phase, and YBa 2 Cu 3 O y (YBCO or Y123) are described. Advanced 4K-Giford-Mcmahon (GM) refrigerator on the market put superconductor coil made of low temperature superconductor metals to practical use and extends its application field. Small laboratory is able to experiment on the high temperature superconductor materials. (S.Y.)

  18. Positron annihilation in a high-temperature superconductor YBa2Cu3O7-δ

    International Nuclear Information System (INIS)

    Vavryshchuk, Ya.; Levandovski, M.; Rybakov, V.N.; Yutlandov, I.A.

    1988-01-01

    Positron annihilation as a function of temperature in high-temperature superconductors YBa 2 Cu 3 O 7-δ has been investigated. It is shown that a change in the annihilation capacity at the transition into superconducting state is relatively small. The change of r 1 and r 2 positron lifetimes as well as of the intensity of the component with r 2 -J 2 and Doppler broadening S parameter allows one to assume that transition into superconducting state is accompanied with a certain decrease in electron density and with decreasing number of defects or increasing size of crystalline net

  19. Magnetic-Field-Induced Soft-Mode Quantum Phase Transition in the High-Temperature Superconductor La1.855Sr0.145CuO4

    DEFF Research Database (Denmark)

    Chang, J.; Christensen, Niels Bech; Niedermayer, C.

    2009-01-01

    Inelastic neutron-scattering experiments on the high-temperature superconductor La1.855Sr0.145CuO4 reveal a magnetic excitation gap Delta that decreases continuously upon application of a magnetic field perpendicular to the CuO2 planes. The gap vanishes at the critical field required to induce long...

  20. Praseodymium valency from crystal structure in Pr-Ba-Cu-O and (Y-Pr)-Ba-Cu-O single crystals

    International Nuclear Information System (INIS)

    Collin, G.; Albouy, P.A.; Monod, P.; Ribault, M.

    1990-01-01

    The substitution of Pr to Y leads to materials with a general formula (Y 1-v Pr v ) (Ba 2-x Pr x ) (Cu 3-y vac y ) O 6+x/2-y+z and with a structural transition around v + x' ∼ 0.5. For v + x 0.5 the crystals are tetragonal, La 1.5 Ba 1.5 Cu 3 O 7±z type, with the characteristic tri-twinning of this phase. The Pr valency, in the range 3-3.2 + depending on preparation conditions, is determined from interatomic distances. Orthorhombic crystals of Pr Ba Cu O prepared at high temperatures exhibit a high amount of defects, y ∼ 0.25 on the Cu(1) site and are semiconductors with a T -1/4 activation law attributed to the praseodymium valence fluctuation

  1. O vacancy formation in (Pr/Gd)BaCo2O5.5 and the role of antisite defects

    KAUST Repository

    Omotayo Akande, Salawu

    2017-04-20

    In search for materials for intermediate temperature solid oxide fuel cells, (Pr/Gd)BaCo2O5.5 is investigated by first principles calculations. Antisite defects are considered as they may modify the electronic and O diffusion properties but are rarely studied in double perovskite oxides. Octahedrally coordinated Co atoms are shown to realize intermediate and high spin states for PrBaCo2O5.5 and GdBaCo2O5.5, respectively, while pyramidally coordinated Co atoms always have high spin. It turns out that O vacancy formation is significantly easier in PrBaCo2O5.5 than in GdBaCo2O5.5, the difference in formation energy being hardly modified by antisite defects. While pyramidally coordinated Co atoms are not affected, we show that the presence of antisite defects causes parts of the octahedrally coordinated Co atoms to switch from intermediate to high spin.

  2. Stability of Tl-Ba-Ca-Cu-O superconducting thin films

    International Nuclear Information System (INIS)

    Siegal, M. P.; Overmyer, D. L.; Venturini, E. L.; Padilla, R. R.; Provencio, P. N.

    1999-01-01

    We report the stability of TlBa 2 CaCu 2 O 7 and Tl 2 Ba 2 CaCu 2 O 8 on LaAlO 3 (100) epitaxial thin films, under a variety of conditions. All films are stable in acetone and methanol and with repeated thermal cycling to cryogenic temperatures. Moisture, especially vapor, degrades film quality rapidly. These materials are stable to high temperatures in either N 2 or O 2 ambients. While total degradation, resulting from Tl depletion, occurs at the same temperatures for both phases, 600 degree sign C in N 2 and 700 degree sign C in O 2 , the onset of degradation occurs at somewhat lower temperatures for TlBa 2 CaCu 2 O 7 than for Tl 2 Ba 2 CaCu 2 O 8 . (c) 1999 Materials Research Society

  3. Magnetic, electrical and structural properties of the Re-doped ruthenocuprate Ru{sub 1−x}Re{sub x}Sr{sub 2}GdCu{sub 2}O{sub y}

    Energy Technology Data Exchange (ETDEWEB)

    Corredor, L.T. [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil); Programa de Pós-Graduação em Ciências de Materiais-CCEN, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil); Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, Bogotá D.C. (Colombia); Albino Aguiar, J. [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil); Programa de Pós-Graduação em Ciências de Materiais-CCEN, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil); Landínez Téllez, D.A. [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, Bogotá D.C. (Colombia); Pureur, P.; Mesquita, F. [Instituto de Física, Universidade Federal do Rio Grande do Sul, 91501-970 Porto Alegre, RS (Brazil); Roa-Rojas, J. [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, Bogotá D.C. (Colombia)

    2015-06-15

    Highlights: • We investigated the effect of the dilution of magnetic Ru sub-lattice of RuSr{sub 2}GdCu{sub 2}O{sub 8}. • We synthesized the doped compound Rui{sub x}Re{sub x}Sr{sub 2}GdCu{sub 2}O{sub y}, for 3%, 6%, 9% and 12% Re. • Re would affect the electron coupling: just 3 and 6% samples were superconductor. • Superconductivity emergence strongly affects magnetic properties of 3 and 6% samples. • A weak ferromagnetic component is consistent with a globally antiferromagnetic system. - Abstract: Despite the discovery of new superconductors classes, high-Tc oxides continue to be a current topic, because of their complex phase diagrams and doping-dependant effects (allowing one to investigate the interaction between orbitals), as well as structural properties such as lattice distortion and charge ordering, among many others. Ruthenocuprates are magnetic superconductors in which the magnetic transition temperature is much higher than the critical superconducting temperature, making them unique compounds. With the aim of investigating the dilution of the magnetic Ru sub-lattice, we proposed the synthesis of the Ru{sub 1−x}Re{sub x}Sr{sub 2}GdCu{sub 2}O{sub y} ruthenocuprate-type family, adapting the known two-step process (double perovskite + CuO) by directly doping the double perovskite, thus obtaining the perovskite compound Sr{sub 2}GdRu{sub 1−x}Re{sub x}O{sub y}, which represents a new synthesis process to the best of our knowledge. Our samples were structurally characterized through X-ray diffraction, and the patterns were analysed via Rietveld refinement. A complete magnetic characterization as a function of temperature and applied field, as well as transport measurements were carried out. We discuss our results in the light of the two-lattice model for ruthenocuprates, and a relation between RuO{sub 2} (magnetic) and CuO{sub 2} (superconductor) sub-lattices can clearly be observed.

  4. Low-temperature specific heat of single-crystal Bi2CaSr2Cu2O8 and Tl2Ca2Ba2Cu3O10

    International Nuclear Information System (INIS)

    Urbach, J.S.; Mitzi, D.B.; Kapitulnik, A.; Wei, J.Y.T.; Morris, D.E.; Physics Division, Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720)

    1989-01-01

    We report specific-heat measurements from 2 to 15 K on single crystals of Bi 2 CaSr 2 Cu 2 O 8 and Tl 2 Ca 2 Ba 2 Cu 3 O 10 We find low-temperature deviations from the Debye law that can be attributed to spin-glass behavior of a small concentration of isolated impurity copper moments. At higher temperatures, we observe contributions to the specific heat that can be attributed to a soft-phonon mode, possibly associated with the superstructure in the Bi-O and Tl-O layers. From our single-crystal data, we conclude that the thallium- and bismuth-based copper oxide superconductors show no measurable linear term in the specific heat [γ(0) less than or equal to 1 mJ/mole K 2

  5. BaO-Nd2O3-CuOx subsolidus equilibria under carbonate-free conditions at pO2=100 Pa and at pO2=21 kPa

    International Nuclear Information System (INIS)

    Wong-Ng, W.; Cook, L.P.; Suh, J.; Coutts, R.; Stalick, J.K.; Levin, I.; Huang, Q.

    2003-01-01

    Subsolidus phase equilibria of the BaO-Nd 2 O 3 -CuO x system at pO 2 =100 Pa (0.1% O 2 volume fraction, 810 deg. C) and at pO 2 =21 kPa (21% O 2 volume fraction, 930 deg. C) have been investigated by applying controlled-atmosphere methods to minimize the presence of carbonate and CO 2 and H 2 O contamination. Under carbonate-free conditions, the BaO-Nd 2 O 3 -CuO x phase diagrams at pO 2 =100 Pa and at pO 2 =21 kPa are similar to one another except for differences in the extent of the solid solutions. Apart from the limiting binary phases, the ternary system consists of three solid solutions and one stoichiometric ternary compound. The first solid solution is the high T c series, Ba 2-x Nd 1+x Cu 3 O 6+z (0.3≥x≥0 at pO 2 =100 Pa; 0.95≥x≥ 0 at pO 2 =21 kPa). At pO 2 =21 kPa, a compositionally dependent phase change was detected, from tetragonal (0.7>x≥0) to orthorhombic (0.95≥x≥0.7). The second solid solution series, the 'brown-phase' Ba 1+x Nd 2-x CuO z , has a narrow homogeneity region (0.10>x≥0 at pO 2 =100 Pa; 0.15>x≥0 at pO 2 =21 kPa). In the high BaO part of the phase diagram, a third solid solution (Ba 2-x Nd x )CuO 3+z (x=0 to ∼ 0.3 at pO 2 =100 Pa; x=0-0.45 at pO 2 =21 kPa) was confirmed, as well as a nominally stoichiometric phase, Ba 4 Nd 2 Cu 2 O z . The latter phase is an insulator, with a structure comprised of unusual CuO 5 linear chains. A significant difference in tie line distribution involving the Ba 2-x Nd 1+x Cu 3 O 6+z superconductor was found under carbonate-free conditions relative to literature studies completed in air. Instead of the BaCuO 2+x -Ba 2+x Nd 4-x Cu 2 O z tie line normally encountered in air, a Ba 2-x Nd 1+x Cu 3 O 6+z -(Ba,Nd) 2 CuO 3+x tie line was established. This tie line substantially expands the field of stability of the Ba 2-x Nd 1+x Cu 3 O 6+z superconductor phase into the BaO-rich region of the phase diagram. Implications for the processing of materials based on the Ba 2-x Nd 1+x Cu 3 O 6+z

  6. Band spectrum transformation and temperature dependences of thermoelectric power of Hg1-xRxBa2Ca2Cu3O8+δ system

    Directory of Open Access Journals (Sweden)

    M. Vasyuk

    2011-03-01

    Full Text Available Temperature dependences of thermoelectric power S(T at T>Tc of the Hg-based high temperature superconductors Hg1-xRxBa2Ca2Cu3O8+δ (R=Re, Pb have been analyzed with accounting for strong scattering of charge carriers. Transformation of parameters of a narrow conducting band in the region of the Fermi level was studied. The existence of correlation between the effective bandwidth and the temperature of a superconductive transition Tc is shown.

  7. Critical current density and wire fabrication of high-TC superconductors

    International Nuclear Information System (INIS)

    Schlabach, T.D.; Jin, S.; Sherwood, R.C.; Tiefel, T.H.

    1989-01-01

    In this paper, some of the recent investigations of wire fabrication techniques and critical current behavior in high T c superconductors will be reviewed. In spite of the tremendous interest and research effort, the progress toward major applications of the bulk high-temperature superconductors has been impeded by, among other thins, the low critical currents and their severe deterioration in weak magnetic fields. Significant advances, however, have been made in understanding the causes of the problem as well as in improving the current-carrying capacity through proper microstructural control such as the melt-textured-growth in Y-Ba-Cu-O. The low density of effective flux-pinning sites in bulk Y-Ba-Cu-O limits J c at 77K in high magnetic fields to about 10 4 A/cm 2 even in the absence of weak links. Magnetization measurements on Bi-Sr-Ca-Cu-O and Tl-Ba-Ca-Cu-O at 77K by various researchers indicate even weaker flux pinning capabilities in these materials than in Y-Ba-Cu-O. The challenge in the future is to obtain suitable flux-pinning defects by choosing the right processing and chemistry changes

  8. Josephson magnetization of Y--Ba--Cu--O superconductors near the critical temperature

    International Nuclear Information System (INIS)

    Ivanchenko, Y.M.; Lisyansky, A.A.; Tsindlekht, M.I.

    1991-01-01

    Experimental and theoretical data for the rectifying properties in a ceramic Y--Ba--Cu--O cylindrical sample are presented. A sample is subjected to the influence of a very small perturbation just to have the linear rectifying regime. Theoretical analysis using the Josephson medium concept gives qualitative agreement with the observed experimental results

  9. Formation pathways in the synthesis and properties of (Tl0.5Pb0.5)(Sr0.9Ba0.1)2Ca2Cu3Oz and (Tl0.5Pb0.5)(Sr0.8Ba0.2)2Ca2Cu3Oz-1223 superconductors

    International Nuclear Information System (INIS)

    Auinger, M; Gritzner, G; Bertrand, Ch; Galez, Ph; Soubeyroux, J-L

    2007-01-01

    The formation pathway of (Tl 0.5 Pb 0.5 )(Sr 0.9 Ba 0.1 ) 2 Ca 2 Cu 3 O z and (Tl 0.5 Pb 0.5 )(Sr 0.8 Ba 0.2 ) 2 Ca 2 Cu 3 O z was studied by neutron and x-ray diffraction. The following reaction pathway was proposed: thallium oxide and lead oxide react with Sr-rich (Sr 1-x Ca x )CuO 2 and Ca-rich (Ca x Sr 1-x )O to form Sr 4 Tl 2 O 7 and (Ca x Sr 1-x )PbO 3 , respectively. The thallate and the plumbate compounds then form the (Tl 0.5 Pb 0.5 )-1212 phase starting at a temperature of 600 deg. C. Finally, between 850 and 900 deg. C, the 1223 phase is formed from (Tl 0.5 Pb 0.5 )-1212 (Ca x Sr 1-x ) 2 CuO 3 and CuO. Parallel experiments to fabricate the (Tl, Pb)-1223 superconductor resulted in specimens with critical temperatures of 117.5 K and 116 K, respectively, and transition widths of 2 K. Differences between the pathways for the formation of Pb-doped, Sr-rich and Pb-free, Ba-rich Tl-1223 superconductors are discussed

  10. Magnetic, electrical and structural properties of the Re-doped ruthenocuprate Ru1−xRexSr2GdCu2Oy

    International Nuclear Information System (INIS)

    Corredor, L.T.; Albino Aguiar, J.; Landínez Téllez, D.A.; Pureur, P.; Mesquita, F.; Roa-Rojas, J.

    2015-01-01

    Highlights: • We investigated the effect of the dilution of magnetic Ru sub-lattice of RuSr 2 GdCu 2 O 8 . • We synthesized the doped compound Rui x Re x Sr 2 GdCu 2 O y , for 3%, 6%, 9% and 12% Re. • Re would affect the electron coupling: just 3 and 6% samples were superconductor. • Superconductivity emergence strongly affects magnetic properties of 3 and 6% samples. • A weak ferromagnetic component is consistent with a globally antiferromagnetic system. - Abstract: Despite the discovery of new superconductors classes, high-Tc oxides continue to be a current topic, because of their complex phase diagrams and doping-dependant effects (allowing one to investigate the interaction between orbitals), as well as structural properties such as lattice distortion and charge ordering, among many others. Ruthenocuprates are magnetic superconductors in which the magnetic transition temperature is much higher than the critical superconducting temperature, making them unique compounds. With the aim of investigating the dilution of the magnetic Ru sub-lattice, we proposed the synthesis of the Ru 1−x Re x Sr 2 GdCu 2 O y ruthenocuprate-type family, adapting the known two-step process (double perovskite + CuO) by directly doping the double perovskite, thus obtaining the perovskite compound Sr 2 GdRu 1−x Re x O y , which represents a new synthesis process to the best of our knowledge. Our samples were structurally characterized through X-ray diffraction, and the patterns were analysed via Rietveld refinement. A complete magnetic characterization as a function of temperature and applied field, as well as transport measurements were carried out. We discuss our results in the light of the two-lattice model for ruthenocuprates, and a relation between RuO 2 (magnetic) and CuO 2 (superconductor) sub-lattices can clearly be observed

  11. Magneto-optical Signatures of a Cascade of Transitions in La 1.875Ba 0.125CuO 4

    Energy Technology Data Exchange (ETDEWEB)

    Karapetyan, Hovnatan; Hucker, M.; Gu, G.D.; Tranquada, J.M.; Fejer, M.M.; Xia, Jing; Kapitulnik, A.

    2012-09-14

    Recent experiments on the original cuprate high temperature superconductor, La{sub 2-x}Ba{sub x}CuO{sub 4}, revealed a remarkable sequence of phase transitions. Here we investigate such crystals with polar Kerr effect which is sensitive to time-reversal-symmetry breaking. Concurrent birefringence measurements accurately locate the structural phase transitions from high-temperature tetragonal to low temperature orthorhombic, and then to lower temperature tetragonal, at which temperature a strong Kerr signal onsets. Hysteretic behavior of the Kerr signal suggests that time-reversal symmetry is already broken well above room temperature, an effect that was previously observed in high quality YBa{sub 2}Cu{sub 3}O{sub 6+x} crystals.

  12. Hall effect in high- Tc Y 1Ba 2Cu 3O 7-δ superconductor

    Science.gov (United States)

    Vezzoli, G. C.; Burke, T.; Moon, B. M.; Lalevic, B.; Safari, A.; Sundar, H. G. K.; Bonometti, R.; Alexander, C.; Rau, C.; Waters, K.

    1989-04-01

    We have performed point-by-point and continuous Hall effect experiments as a function of temperature in polycrystalline Y 1Ba 2Cu 3O 7-δ. We have shown that the positive Hall constant shows an abrupt increase upon decreasing temperature at a value just above Tc. This temperature corresponds to where the resistance versus temperature data deviates from linearity. At very high fields of 6.8 and 15 T we observe a subsequent decrease in RH. We interpret these data as supportive of a contribution toward the superconductivity mechanism arising from internal excitions or change transfer excitations such that the bound exciton concentration increases near Tc at the expense of positive carries which are reflected in both bound and free holes.

  13. Microstructure and Properties of High-Temperature Superconductors

    CERN Document Server

    Parinov, Ivan A

    2007-01-01

    The main features of high-temperature superconductors (HTSC) that define their properties are intrinsic brittleness of oxide cuprates, the layered anisotropic structure and the supershort coherence length. Taking into account these features, this treatise presents research into HTSC microstructure and properties, and also explores the possibilities of optimization of the preparation techniques and superconducting compositions. The "composition-technique-experiment-theory-model," employed here, assumes considerable HTSC defectiveness and structure heterogeneity and helps to draw a comprehensive picture of modern representations of the microstructure, strength and the related structure-sensitive properties of the materials considered. Special attention is devoted to the Bi-Sr-Ca-Cu-O and Y-Ba-Cu-O families, which currently offer the most promising applications. Including a great number of illustrations and references, this monograph addresses students, post-graduate students and specialists, taking part in the ...

  14. Microstructure and Properties of High-Temperature Superconductors

    CERN Document Server

    Parinov, I A

    2012-01-01

    The main features of high-temperature superconductors (HTSC) that define their properties are intrinsic brittleness of oxide cuprates, the layered anisotropic structure and the supershort coherence length. Taking into account these features, this treatise presents research into HTSC microstructure and properties, and also explores the possibilities of optimization of the preparation techniques and superconducting compositions. The "composition-technique-experiment-theory-model," employed here, assumes considerable HTSC defectiveness and structure heterogeneity and helps to draw a comprehensive picture of modern representations of the microstructure, strength and the related structure-sensitive properties of the materials considered. Special attention is devoted to the Bi-Sr-Ca-Cu-O and Y-Ba-Cu-O families, which currently offer the most promising applications. Including a great number of illustrations and references, this monograph addresses students, post-graduate students and specialists, taking part in the ...

  15. Solubility and superconductivity in RE(Ba2-xREx)Cu3O7+δ (RE = Nd, Sm, Eu, Gd, Dy)

    International Nuclear Information System (INIS)

    Zhang, K.; Dabrowski, B.; Segre, C.U.; Hinks, D.G.; Schuller, I.K.; Jorgensen, J.D.; Slaski, M.

    1987-10-01

    Solid solutions of RE(Ba 2-x RE x )Cu 3 O 7- δ (RE=Nd,Sm,Eu,Gd,Dy) for x=0 to x=0.5 have been investigated. X-ray and resistivity measurements show that there exists a solid solution region, through which, the structure changes from orthorhombic to tetragonal and the superconducting properties are depressed. The solubility limits depend strongly on the size of the rare-earth ion, with the smallest (Dy) showing no appreciable solubility. The superconducting transition temperature versus x for all of the rare-earth ion substitutions falls on a universal curve, indicating that the Ba sites are extremely ionic and magnetically isolated. 20 refs., 4 figs

  16. The Structural Evolution of (Gd, Y)Ba2Cu3Ox Tapes With Zr Addition Made by Metal Organic Chemical Vapor Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lei, CH; Galstyan, E; Chen, YM; Shi, T; Liu, YH; Khatri, N; Liu, JF; Xiong, XM; Majkic, G; Selvamanickam, V

    2013-06-01

    Structural analysis of (Gd, Y) Ba2Cu3Ox tapes with Zr addition made by metal organic chemical vapor deposition has been conducted with transmission electron microscopy and X-ray diffraction. Zr content in the films was varied from 0 to 25% in the precursor. In all Zr-doped films, self-assembled nanocolumnar structures of BaZrO3 (BZO) were observed along the c-axis. The amount of BaZrO3 was found to increase steadily with Zr content. Additionally, planar BZO plates were found on the (001) plane of (Gd, Y) Ba2Cu3Ox film. The size and thickness of BZO plates were seen to increase with Zr doping level. Rare-earth copper oxide phases were observed to begin to emerge in the 20% Zr-doped film. Cross-sectional study of the interface between (Gd, Y)Ba2Cu3Ox and LaMnO3 cap layer revealed a thin discrete BZO layer on the LaMnO3 in the 20% Zr doped film.

  17. High-temperature superconductors induced by ion implantation. Final report

    International Nuclear Information System (INIS)

    Greenwald, A.C.; Johnson, E.

    1988-08-01

    High dose oxygen ion implantation (10 to the 17th power ions per sq. cm.) at elevated temperatures (300 C) has been shown to adjust the critical temperature of gamma-Y-Ba-Cu-O and Bi-Ca-Sr-Cu-O materials. These results are in marked contrast to earlier work which showed complete destruction of superconducting properties for similar radiation doses, and marked reduction in superconducting properties at one-tenth this dose in the 1-2-3- compound only. Experiments also showed that the superconducting materials can be patterned into conducting and nonconducting areas without etching by ion implantation, allowing maintenance of planar geometries required for microcircuit fabrication. Experiments on deposition of thin films of high temperature superconductors for use with the ion implantation experiments showed that ion beam sputtering from a single target could achieve the correct stoichiometry. Variations of composition with ion beam energy and angle of sputtered ions were studied

  18. Stability of Tl-Ba-Ca-Cu-O superconducting thin films

    Energy Technology Data Exchange (ETDEWEB)

    Siegal, M. P. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Overmyer, D. L. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Venturini, E. L. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Padilla, R. R. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Provencio, P. N. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States)

    1999-12-01

    We report the stability of TlBa{sub 2}CaCu{sub 2}O{sub 7} and Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8} on LaAlO{sub 3}(100) epitaxial thin films, under a variety of conditions. All films are stable in acetone and methanol and with repeated thermal cycling to cryogenic temperatures. Moisture, especially vapor, degrades film quality rapidly. These materials are stable to high temperatures in either N{sub 2} or O{sub 2} ambients. While total degradation, resulting from Tl depletion, occurs at the same temperatures for both phases, 600 degree sign C in N{sub 2} and 700 degree sign C in O{sub 2}, the onset of degradation occurs at somewhat lower temperatures for TlBa{sub 2}CaCu{sub 2}O{sub 7} than for Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8}. (c) 1999 Materials Research Society.

  19. The microscopic twins and their crystal phase in the high Tc Y-Ba-Cu-O and Dy-Ba-Cu-O superconductive ceramics

    International Nuclear Information System (INIS)

    Zu, Z.J.; Chen, Y.L.

    1988-01-01

    Most consider that the structure of Y-Ba- Cu-O and Dy-Ba-Cu-O stable superconductive crystals with high Tc is associated with the right-angled phase. The superconductivity is closely connected with the right-angled character of the crystalline texture; the better the right- angled character, the better the superconductivity. From statistical investigations of examples the authors have discovered that most of the Y-Ba-Cu-O and Dy-Ba-Cu-O superconductivity with high Tc ceramic crystals is in the monoclinic phase, which, consists of microscopic, lamellar, single twins. The long-columnar grains consisting of lamellar twin slabs show the optical characteristics of right-angled phase. The microscopic twinning and grain morphologies are summarized in this paper

  20. Stress-strain behavior under static loading in Gd123 high-temperature superconductors at 77 K

    Science.gov (United States)

    Fujimoto, Hiroyuki; Murakami, Akira; Teshima, Hidekazu; Morita, Mitsuru

    2013-10-01

    Mechanical properties of melt-growth GdBa2Cu3Ox (Gd123) superconducting samples with 10 wt.% Ag2O and 0.5 wt.% Pt were evaluated at 77 K through flexural tests for specimens cut from the samples in order to estimate the mechanical properties of the Gd123 material without metal substrates, buffer layers or stabilization layers. We discuss the mechanical properties; the Young's modulus and flexural strength with stress-strain behavior at 77 K. The results show that the flexural strength and fracture strain of Gd123 at 77 K are approximately 100 MPa and 0.1%, respectively, and that the origin of the fracture is defects such as pores, impurities and non-superconducting compounds. We also show that the Young's modulus of Gd123 is estimated to be 160-165 GPa.

  1. Thermal conductivity of ferrimagnet GdBaMn2O5.0 single crystals

    Directory of Open Access Journals (Sweden)

    J. C. Wu

    2017-05-01

    Full Text Available GdBaMn2O5.0 is a double-perovskite ferrimagnet consisting of pyramidal manganese layers. In this work, we study the in-plane and the c-axis thermal conductivities of GdBaMn2O5.0 single crystals at low temperatures down to 0.3 K and in high magnetic fields up to 14 T. The κc(T curve shows a broad hump below the Néel temperature (TN = 144 K, which indicates the magnon heat transport along the c axis. Whereas, the κa(T shows a kink at TN, caused by a magnon-phonon scattering effect. This anisotropic behavior is caused by the anisotropy of spin interactions along different directions. At very low temperatures, magnetic-field-induced changes of κa and κc, which is likely due to phonon scattering by free Gd3+ spins, is rather weak. This indicates that the spin coupling between Gd3+ and Mn2+/Mn3+ is rather strong at low temperatures.

  2. Properties of Y Ba2 Cu3 O7-x-Ag prepared by the citrate technique

    International Nuclear Information System (INIS)

    Fonseca, Fabio Coral

    1996-01-01

    Y Ba 2 Cu 3 O 7-x (Y123) ceramic superconductor and YBa 2 Cu 3 O 7-x- Ag composite superconductors have been prepared by the citrate technique. Microstructural analysis has been done by X-ray diffractometry and optical ceramography. The superconducting behavior has been studied by 4 probe dc electrical resistivity in the 77 K - 140 K temperature range. Silver percolation in the ceramic matrix was studied by electrical resistivity measurements at room temperature; the percolation threshold was found to be approximately 25 vol. % (35.5 wt. %) Ag. Specimens with silver addition showed improvement in the flexural strength of the Y123 compound. The main results show that the critical temperatures does not depend on the silver content in the composite specimens, the normal state electrical behavior of the superconductor is affected by silver addition and approximately 3 wt. % (1.8 vol. %) Ag doping yields and optimized composite superconductor from the electrical, mechanical and microstructural pont of view, with platelet-like grain shapes. (author)

  3. Dielectric relaxations in non-metallic materials related to Y-Ba-Cu-O superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bennani, H.; Pilet, J.C. (Lab. Instrumentation, Rennes-1 Univ., 35 (France)); Guilloux-Viry, M.; Perrin, C.; Perrin, A.; Sergent, M. (Lab. de Chimie Minerale B, C.N.R.S., 35 - Rennes (France))

    1990-10-15

    In relation with high Tc superconducting material studies, dielectric measurements have been carried out, in the frequency range 10 Hz - 100 kHz, on two powdered compounds belonging to the Y-Ba-Cu-O system. The non-metallic tetragonal phases YBa{sub 2}Cu{sub 3}O{sub 6+x} exhibit dielectric relaxations: for the studied samples (x<0.4) the activation energy U is observed in the range 0.5Cu-O chains. The insulating green phase Y{sub 2}BaCuO{sub 5} has a lower activation energy U {approx equal} 0.4 eV and an entropy factor A {approx equal} 10{sup 10} Hz. A second dielectric relaxation has been detected at higher temperature, near 400 K. Additional measurements to 77 K at 1 MHz give a value of dielectric constant {epsilon}'=3 and a low loss factor tg{delta}=10{sup -3}: this latter value is comparable to the one of lanthanum gallate recently proposed as a substrate for high frequency uses. This result enhances the previously reported potential interest of this material as substrate or buffer layer for preparation of superconducting thin films for high frequency applications. (orig.).

  4. Giant Tc shift in HgBa2CaCu2O6+δ and TlBa2CaCu2O7-δ superconductors due to Hg-Tl exchange

    International Nuclear Information System (INIS)

    Gapud, A.A.; Wu, J.Z.; Kang, B.W.; Yan, S.L.; Xie, Y.Y.; Siegal, M.P.

    1999-01-01

    The irreversibility lines of epitaxial thin films of HgBa 2 CaCu 2 O 6+δ and TlBa 2 CaCu 2 O 7-δ , whether deduced from field-induced magnetoresistive broadening or onset of nonhysteretic magnetization, were found to coincide when plotted against reduced temperature, showing the same exponential-decay temperature behavior for T/T c c >0.8 (where T c is zero-field, zero-resistivity critical temperature). These results indicate that replacing Tl with Hg has no noticeable effect on the anisotropy and suggests that T c is not determined by anisotropy. copyright 1999 The American Physical Society

  5. Investigation of (Y,Gd)Ba{sub 2}Cu{sub 3}O{sub 7-x} grown by MOCVD on a simplified IBAD MgO template

    Energy Technology Data Exchange (ETDEWEB)

    Stan, L; Holesinger, T G; Maiorov, B; Civale, L; DePaula, R F; Jia, Q X [Los Alamos National Laboratory, PO Box 1663, Los Alamos, NM 87545 (United States); Chen, Y [SuperPower, Incorporated, 450 Duane Avenue, Schenectady, NY 12304 (United States); Xiong, X; Selvamanickam, V [Mechanical Engineering Department, University of Houston, Houston, TX 77204-4006 (United States)

    2010-01-15

    We have used an ion beam sputtered Y{sub 2}O{sub 3}-Al{sub 2}O{sub 3} (YALO) composite to simplify the architecture of high temperature superconducting (HTS) coated conductors (CCs) based on a IBAD MgO template. By implementing YALO, we have reduced the total non-superconducting layers between the polycrystalline metal substrate and the superconducting film from five (the standard architecture) to four. Well textured (Y,Gd)Ba{sub 2}Cu{sub 3}O{sub 7-x} ((Y, Gd)BCO) films have been successfully grown by MOCVD on this simplified template. The microstructural characterization revealed that all layers are continuous and uniform with sharp and clean interfaces. Additionally, the YALO maintained its amorphous nature after the deposition of the superconductive layer, which is a plus in terms of its efficiency as a diffusion barrier. The achievement of a self-field critical current of 230 A cm{sup -1} at 75.5 K is another proof of the effectiveness of YALO as a diffusion barrier and nucleation seed for the MgO. The transport properties under an applied magnetic field of MOCVD grown (Y, Gd)BCO on LMO buffered MgO/YALO/Ni-alloy are comparable with those of (Y, Gd)BCO on a standard architecture, thus demonstrating good compatibility between the simplified template with the MOCVD grown (Y, Gd)BCO. The use of a single composite YALO layer instead of individual layers of Y{sub 2}O{sub 3} and Al{sub 2}O{sub 3} for the large scale fabrication of HTS CCs based on IBAD MgO provides advantages such as potentially reduced cost due to the reduced number of fabrication steps.

  6. Magnetic field orientation dependence of flux pinning in (Gd,Y)Ba2Cu3O7-x coated conductor with tilted lattice and nanostructures

    International Nuclear Information System (INIS)

    Zhang, Y.; Specht, E.D.; Cantoni, C.; Christen, D.K.; Thompson, J.R.; Sinclair, J.W.; Goyal, A.; Zuev, Y.L.; Aytug, T.; Paranthaman, M.P.; Chen, Y.; Selvamanickam, V.

    2009-01-01

    The dependence of the critical current density (J c ) on the orientation of an applied magnetic field was studied for a prototype (Gd,Y)Ba 2 Cu 3 O 7-x (GdYBCO) coated conductor fabricated by MOCVD on an IBAD-MgO template. Additional rare-earth cations (Y and Gd) and Zr were incorporated into the superconducting film to form (Y,Gd) 2 O 3 and BaZrO 3 nanoparticles extended nearly parallel to the a-b planes and to the c-axis, respectively, to enhance the flux pinning. In-field measurement of J c was carried out with electrical current flowing either along or perpendicular to the longitudinal axis of the tape, while a maximum Lorentz force configuration was always maintained. Details in the angular dependence of J c were related to the unique structure of the film, specifically the tilt in the GdYBCO lattice and the tilts in the extended (Y,Gd) 2 O 3 and BaZrO3 nanoparticles. XRD and TEM were used to study the structure of the coated conductor. The effect of the misalignment between the external field H and the internal field B on the angular dependence of J c is discussed.

  7. Creation of the best performance high-$T_{c}$ superconductor based on Cu-1234

    CERN Document Server

    Ihara, H; Iyo, A; Kito, H; Terada, N; Tokumoto, M; Ishida, K; Sekita, Y; Yamamoto, H; Hayashi, H; Khan, N A; Sundaresan, A; Nie, J; Harashima, E; Ishiura, Y; Tateai, F; Kawamura, M

    1999-01-01

    The purpose of this project is to create the best performance superconductor on the basis of our original Cu-1234 (CuBa/sub 2/Ca /sub 3/Cu/sub 4/O/sub 12-y/) superconductor. Its best performance superconductor will be realized by the modification of superconducting wave function (MSWF) and application of new preparation techniques of thin films. The MSWF leads to the enhancement of coherence length along the c-axis and transformation from d-wave to (d+is)-wave, and then low superconducting anisotropy. The thin film techniques are APE (amorphous phase epitaxy) method and SAE (self assembling epitaxy) method by using a structure stabilizer such as Tl. The best superconductor with long coherence length, low anisotropy, high T/sub c/, high J/sub c/ and high H/sub irr/ will be realized for wire and Josephson junctions and microwave device application at 77 K. (16 refs).

  8. Optimization in the preparation of the YBa2Cu3O7-δ compound using BaCO3 and BaO2 reagents

    International Nuclear Information System (INIS)

    Bustamante D, A.; Flores S, J.

    2004-01-01

    The traditional superconductor YBa 2 Cu 3 O 7-δ (Y123) has an orthorhombic crystalline structure with spatial group Pmmm and its critical temperature is 90K. The literature reports the use of reagent BaCO 3 for the preparation by the solid state reaction which requires one calcination and two thermal treatments in oxygen flow at 950 o C. In this work we report the comparison in the preparation of Y123 using the BaO 2 reagent as another possibility for preparation; in this case we have used only two thermal treatments in oxygen flow at 950 o C; therefore reducing the costs in preparation. The powder XRD pattern of samples prepared with BaO 2 confirm a well crystallized phase an the diffraction lines of the main phase can be indexed with an orthorhombic unit cell. The ac susceptibility measurement in the range 5-100 K using a Quantum Design (SQUID) magnetometer for two samples confirms the superconductor behavior with critical temperature Tc ≅ 91 K. The critical temperatures for these systems were found taken account the derivatives of the susceptibility curves. Scanning Electron Microscopy (SEM) confirms the good behavior of the grains corresponding to both methods. (orig.)

  9. Photoemission study of absorption mechanisms in Bi2.0Sr1.8Ca0.8La0.3Cu2.1O8+δ, BaBiO3, and Nd1.85Ce0.15CuO4

    International Nuclear Information System (INIS)

    Lindberg, P.A.P.; Shen, Z.; Wells, B.O.; Dessau, D.S.; Ellis, W.P.; Borg, A.; Kang, J.; Mitzi, D.B.; Lindau, I.

    1989-01-01

    Photoemission measurements in the constant-final-state (absorption) mode were performed on three different classes of high-temperature superconductors Bi 2.0 Sr 1.8 Ca 0.8 La 0.3 Cu 2.1 O 8+δ , BaBiO 3 , and Nd 1.85 Ce 0.15 CuO 4 using synchrotron radiation from 20 to 200 eV. Absorption signals from all elements but Ce are identified. The results firmly show that the Bi 6s electrons are more delocalized in BaBiO 3 than in Bi 2.0 Sr 1.8 Ca 0.8 La 0.3 Cu 2.1 O 8+δ , in agreement with the results of band-structure calculations. Differences in the absorption signals due to O and Bi excitations between BaBiO 3 and Bi 2.0 Sr 1.8 Ca 0.8 La 0.3 Cu 2.1 O 8+δ are discussed. Delayed absorption onsets attributed to giant resonances (Ba 4d→4f, La 4d→4f, and Nd 4d→4f transitions) are also reported

  10. Production of high temperature superconductors and characteristics by infrared and Raman spectroscopy

    International Nuclear Information System (INIS)

    Thomsen, C.

    1991-01-01

    This final report, which is partly kept short, is concerned with electron/phonon interaction and the determination of the band gap in high temperature superconductors (YBa 2 Cu 3 O 7 ). The final report is divided into four parts, which reflect the individual working groups: 1. Raman spectroscopy, 2. IR spectroscopy (reflection measurements, isotope effect, superconducting energy gap, behaviour of infrared active phonons), 3. Magnetic field measurements, and 4. Theory (initial calculation of the metal/isolator transfer in BaBiO 3 ). (MM) [de

  11. Thermal properties of GdSr{sub 2}RuCu{sub 2}O{sub 8-{delta}} based mixtures in the GdSr{sub 2}RuO{sub 6}-CuO pseudo-binary system

    Energy Technology Data Exchange (ETDEWEB)

    Gombos, Marcello [Laboratorio Regionale Supermat CNR-INFM Via Salvador Allende, I-84081 Baronissi (Italy); Dipartimento di Fisica ' E.R.Caianiello' , Universita di Salerno, Via Salvador Allende, I-84081 Baronissi (Italy)], E-mail: gombos@sa.infn.it; Ciancio, Regina; Vecchione, Antonio; Pace, Sandro [Laboratorio Regionale Supermat CNR-INFM Via Salvador Allende, I-84081 Baronissi (Italy); Dipartimento di Fisica ' E.R.Caianiello' , Universita di Salerno, Via Salvador Allende, I-84081 Baronissi (Italy)

    2007-09-01

    GdSr{sub 2}RuCu{sub 2}O{sub 8-{delta}} (Gd1212) rutheno-cuprate compound is widely studied because it shows the coexistence of superconductivity and highly anisotropic magnetic ordering in the same cell. Anyway the nature of the magnetic ordering is still debated and the fabrication of macroscopic samples oriented along a crystallographic axis, that could help to clarify its details, appears to be quite difficult. For this reason, accurate investigation on Gd1212 incongruent melting reaction, producing liquid copper oxide and the solid GdSr{sub 2}RuO{sub 6} (Gd1210), appears to be necessary to improve the fabrication of crystallographically oriented bulk superconducting samples. Thermo-gravimetric and differential thermal measurements were performed to analyse the thermal behaviour up to 1200 deg. C and the melting temperatures of different mixtures of Gd1212 with Gd1210 or CuO, in view to perform a scan of the whole CuO-Gd1212-Gd1210 coexistence line of the Gd-Sr-Ru-Cu-O phase diagram. Dependence on the atmosphere and the formation of different spurious phases was also studied.

  12. High-speed photography of laser ablation plasmas from the high temperature superconductor YBa2Cu3O7-δ

    International Nuclear Information System (INIS)

    Scott, K.; Huntley, J.M.; Phillips, W.A.

    1993-01-01

    The luminous plume formed by laser ablation of the high-temperature superconductor YBa 2 Cu 3 O 7-δ has been investigated using high-speed framing photography. Variation of the background oxygen pressure was found to significantly influence the velocity distribution of the ablated species, leading in particular to shock wave formation and instabilities on the shock front at higher pressures. Spectral characteristics of the plume were studied using optical interference filters, and two distinct regions of emission were identified. (orig.)

  13. Multilayered cuprate superconductor Ba2Ca5Cu6O12(O1-x,Fx) 2 studied by temperature-dependent scanning tunneling microscopy and spectroscopy

    Science.gov (United States)

    Sugimoto, Akira; Ekino, Toshikazu; Gabovich, Alexander M.; Sekine, Ryotaro; Tanabe, Kenji; Tokiwa, Kazuyasu

    2017-05-01

    Scanning tunneling microscopy/spectroscopy (STM/STS) measurements were carried out on a multilayered cuprate superconductor Ba2Ca5Cu6O12 (O1 -x,Fx )2. STM topography revealed random spot structures with the characteristic length ≤0.5 nm. The conductance spectra d I /d V (V ) show the coexistence of smaller gaps ΔS and large gaps (pseudogaps) ΔL. The pseudogap-related features in the superconducting state were traced with the spatial resolution of ˜0.07 nm. Here, I and V are the tunnel current and bias voltage, respectively. The temperature, T , dependence of ΔS follows the reduced Bardeen-Cooper-Schrieffer (BCS) dependence. The hallmark ratio 2 ΔS(T =0 ) /kBTc equals to 4.9, which is smaller than those of other cuprate superconductors. Here, Tc is the superconducting critical temperature and kB is the Boltzmann constant. The larger gap ΔL survives in the normal state and even increases with T above Tc. The T dependencies of the spatial distributions for both relevant gaps (Δ map), as well as for each gap separately (ΔS and ΔL), were obtained. From the histogram of Δ map, the averaged gap values were found to be Δ¯S=˜24 meV and Δ¯L=˜79 meV. The smaller gap ΔS shows a spatially homogeneous distribution while the larger gap ΔL is quite inhomogeneous, indicating that rather homogeneous superconductivity coexists with the patchy distributed pseudogap. The spatial variation length ξΔ L of ΔL correlates with the scale of the topography spot structures, being approximately 0.4 nm. This value is considerably smaller than the coherence length of this class of superconductors, suggesting that ΔL is strongly affected by the disorder of the apical O/F.

  14. A new series of oxycarbonate superconductors (Cu{sub 0.5}C{sub 0.5}){sub m}Ba{sub m+1}Ca{sub n-1}Cu{sub n}O{sub 2}({sub m+n})+1

    Energy Technology Data Exchange (ETDEWEB)

    Takayama-Muromachi, E.; Kawashima, T.; Matsui, Y. [National Institute for Research in Inorganic Materials, Ibaraki (Japan)

    1994-12-31

    We found a new series of oxycarbonate superconductors in the Ba-Ca-Cu-C-O system under high pressure of 5 GPa. Their ideal formula is (Cu{sub 0.5}C{sub 0.5}){sub m}Ba{sub m+1}Ca{sub n-1}Cu{sub n}O{sub 2}({sub m+n})+1 ((Cu,C)-m(m+1)(n-1)n). Thus far, n=3, 4 members of the m=1 series, (Cu,C)-1223 and (Cu,C)-1234, have been prepared in bulk while n=4, 5 members, (Cu,C)-2334 and (Cu,C)-2345, have been prepared for the m=2 series. (Cu,C)-1223 shows superconductivity below 67 K while T{sub c}`s of other compounds are above 110 K. In particular, (Cu,C)=1234 has the highest T{sub c} of 117 K.

  15. Magnetotransport study of in situ magnetic field textured Dy1Ba2Cu3O7-δ superconductors

    International Nuclear Information System (INIS)

    Pekala, M.; Liege Univ.; Cloots, R.; Liege Univ.; Bougrine, H.; Liege Univ.; Maka, E.; Ausloos, M.

    1995-01-01

    The electrical resistivity, thermoelectric power and the Nernst effect have been studied as a function of temperature and magnetic field for a typical superconductor DyBa 2 Cu 3 O 7-δ magnetically textured in situ at 1035 C. The three transport coefficients show hybrid microscopic features. In particular, we show the anisotropy with respect to the field direction (H // a, H // c) in all transport coefficients. We verify that Tinkham's law is obeyed for the broadening of the resistive transition in a magnetic field. Similarly we obtain anisotropic broadening exponents for each integrated excess property. From Arrhenius plots we obtain orders of magnitude for the activation energies characterizing each property. They are markedly different from each other. (orig.)

  16. Properties of the (Sm sub 0 sub . sub 3 sub 3 Eu sub 0 sub . sub 3 sub 3 Gd sub 0 sub . sub 3 sub 3)Ba sub 2 Cu sub 3 O sub y superconductor prepared by different processes in air

    CERN Document Server

    Giovannelli, F; Monot-Laffez, I

    2003-01-01

    Bars and pellets of the (Sm sub 0 sub . sub 3 sub 3 Eu sub 0 sub . sub 3 sub 3 Gd sub 0 sub . sub 3 sub 3)Ba sub 2 Cu sub 3 O sub x superconductor were processed in air, using the floating zone method and the top-seeded melt-textured growth method, respectively. The samples were prepared using different experimental conditions, i.e. maximal processing temperature, translation rate or cooling rate. Their physical properties and their microstructure were studied. All the samples exhibit a satisfying superconducting transition whereas the critical current density greatly depends on the processing parameters. The sample prepared by the floating zone method at 1070 deg C with a translation rate of 2 mm h sup - sup 1 exhibits a very high J sub c value of 70000 A cm sup - sup 2 in the self-field and more than 30000 A cm sup - sup 2 at 1.7 T. The pellet processed at 1080 deg C with a cooling rate of 2 deg C h sup - sup 1 has a high J sub c reaching about 56000 A cm sup - sup 2 in the self-field and more than 32000 A ...

  17. Reduced flux motion via flux creep annealing in high- Jc single-crystal Y1Ba2Cu3O7

    International Nuclear Information System (INIS)

    Thompson, J.R.; Sun, Y.R.; Malozemoff, A.P.; Christen, D.K.; Kerchner, H.R.; Ossandon, J.G.; Marwick, A.D.; Holtzberg, F.

    1991-01-01

    We investigated the stabilization of magnetic flux in a high-temperature superconductor (a proton-irradiated Y 1 Ba 2 Cu 3 O 7 crystal), by operating with subcritical current density J. Using the thermal history to obtain an induced current density J≤J c , we observed a drastically reduced relaxation rate dM/dt (M=magnetization), after ''flux creep annealing.'' The results show that the field gradient ∼J∼M determined the relaxation rate, independent of the sample's H-T history, in agreement with recent theory

  18. Preparation of silver doped high temperature superconductors

    International Nuclear Information System (INIS)

    Stavek, Jiri; Zapletal, Vladimir

    1989-01-01

    High temperature superconductors were prepared by the controlled double-jet precipitation to manipulate the chemical composition, composition gradients, average grain size, grain size distribution, and other factors which contribute to the actual properties and performance of HTSC. The cations (Y-Ba-Cu or Bi-Pb-Ca-Sr-Cu) and oxalic anions solutions were simultaneously separately introduced to the crystallizer with a stirred solution of gelatin under conditions where the temperature, excess of oxalic anions in solution, pH, reactant addition rate, and other reaction conditions were tightly controlled to prepare the high sinterability powder. To increase the sinterability of submicron particles of produced precursor, the silver ions were introduced at the end of the controlled double-jet precipitation. This approach improves the electrical and mechanical properties of produced HTSC specimens. The controlled double jet precipitation provides a viable technique for preparation of oxide superconductors and the process is amenable for scaling up

  19. Epitaxial heterojunctions of oxide semiconductors and metals on high temperature superconductors

    Science.gov (United States)

    Vasquez, Richard P. (Inventor); Hunt, Brian D. (Inventor); Foote, Marc C. (Inventor)

    1994-01-01

    Epitaxial heterojunctions formed between high temperature superconductors and metallic or semiconducting oxide barrier layers are provided. Metallic perovskites such as LaTiO3, CaVO3, and SrVO3 are grown on electron-type high temperature superconductors such as Nd(1.85)Ce(0.15)CuO(4-x). Alternatively, transition metal bronzes of the form A(x)MO(3) are epitaxially grown on electron-type high temperature superconductors. Also, semiconducting oxides of perovskite-related crystal structures such as WO3 are grown on either hole-type or electron-type high temperature superconductors.

  20. PR IN HIGH-TEMPERATURE SUPERCONDUCTORS - INSULATING PLANES, METALLIC CHAINS

    NARCIS (Netherlands)

    KHOMSKII, D

    Critical discussion is given of the properties of Pr-containing high-T(c) superconductors, especially Y1-xPrxBa2Cu3O7. It is argued that the models proposed to explain suppression of T(c) and other properties of this system (pairbreaking; hole filling; strong p-f hybridization) are inadequate and

  1. Reduced thermal budget processing of Y--Ba--Cu--O high temperature superconducting thin films by metalorganic chemical vapor deposition

    International Nuclear Information System (INIS)

    Singh, R.; Sinha, S.; Hsu, N.J.; Ng, J.T.C.; Chou, P.; Thakur, R.P.S.; Narayan, J.

    1991-01-01

    Metalorganic chemical vapor deposition (MOCVD) has the potential of emerging as a viable technique to fabricate ribbons, tapes, coated wires, and the deposition of films of high temperature superconductors, and related materials. As a reduced thermal budget processing technique, rapid isothermal processing (RIP) based on incoherent radiation as the source of energy can be usefully coupled to conventional MOCVD. In this paper we report on the deposition and characterization of high quality superconducting thin films of Y--Ba--Cu--O (YBCO) on MgO and SrTiO 3 substrates by RIP assisted MOCVD. By using a mixture of N 2 O and O 2 as the oxygen source films deposited initially at 600 degree C for 1 min and then at 740 degree C for 30 min are primarily c-axis oriented and with zero resistance being observed at 84 and 89 K for MgO and SrTiO 3 substrates, respectively. The zero magnetic field current densities at 77 K for MgO and SrTiO 3 substrates are 1.2x10 6 and 1.5x10 6 A/cm 2 , respectively. It is envisaged that high energy photons from the incoherent light source and the use of a mixture of N 2 O and O 2 as the oxygen source, assist chemical reactions and lower overall thermal budget for processing of these films

  2. The Born-Mayer-Huggins potential in high temperature superconductors

    Science.gov (United States)

    Singh, Hempal; Singh, Anu; Indu, B. D.

    2016-07-01

    The Born-Mayer-Huggins potential which has been found the best suitable potential to study the YBa2Cu3O7-δ type high temperature superconductors is revisited in a new framework. A deeper insight in it reveals that the Born-Mayer parameters for different interactions in high temperature superconductor are not simple quantities but several thermodynamic and spatial functions enter the problem. Based on the new theory, the expressions for pressure, bulk modulus and Born-Mayer parameters have been derived and it is established that these quantities depend upon Gruneisen parameter which is the measure of the strength of anharmonic effects in high temperature superconductors. This theory has been applied to a specific model YBa2Cu3O7-δ crystal for the purpose of numerical estimates to justify the new results.

  3. Synthesis, structural characterization and fluctuation conductivity of HoBa2Cu3O7-δ-SrTiO3 composites

    International Nuclear Information System (INIS)

    Uribe Laverde, M.A.; Landinez Tellez, D.A.; Roa-Rojas, J.

    2010-01-01

    Single-phase polycrystalline samples of HoBa 2 Cu 3 O 7-δ superconductor and SrTiO 3 isolator were produced by means of the solid state reaction technique. After structural characterization of both materials, superconductor-isolator composites were produced with nominal isolator volume percentages between 0% and 10%. Resistivity measurements for the composites and the HoBa 2 Cu 3 O 7-δ sample with different currents evidenced a superconducting transition with critical temperature T C = 92 K, with wider transitions with increasing either isolator content or measurement current. Fluctuation conductivity analyses were carried out to obtain the exponents characterizing the conductivity divergence. Above T C , apart from the typical Gaussian and critical fluctuations an atypical regime with critical exponent about 0.14 is observed as a precursor of the transition. Below T C , it is observed that the coherence transition characteristic exponent increases rapidly with increasing isolator percentage in the composites and does not show important changes when modifying the current in the pure superconductor sample.

  4. Magnetic field orientation dependence of flux pinning in (Gd,Y)Ba2Cu3O7-x coated conductor with tilted lattice and nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yifei [ORNL; Specht, Eliot D [ORNL; Cantoni, Claudia [ORNL; Christen, David K [ORNL; Zuev, Yuri L [ORNL; Goyal, Amit [ORNL; Sinclair, J. [University of Tennessee, Knoxville (UTK); Thompson, James R [ORNL; Aytug, Tolga [ORNL; Paranthaman, Mariappan Parans [ORNL; Chen, Y [SuperPower Incorporated, Schenectady, New York; Selvamanickam, V. [SuperPower Incorporated, Schenectady, New York

    2009-01-01

    The dependence of the critical current density (J{sub c}) on the orientation of an applied magnetic field was studied for a prototype (Gd,Y)Ba{sub 2}Cu{sub 3}O{sub 7?x} (GdYBCO) coated conductor fabricated by MOCVD on an IBAD-MgO template. Additional rare-earth cations (Y and Gd) and Zr were incorporated into the superconducting film to form (Y,Gd){sub 2}O{sub 3} and BaZrO{sub 3} nanoparticles extended nearly parallel to the a-b planes and to the c-axis, respectively, to enhance the flux pinning. In-field measurement of J{sub c} was carried out with electrical current flowing either along or perpendicular to the longitudinal axis of the tape, while a maximum Lorentz force configuration was always maintained. Details in the angular dependence of J{sub c} were related to the unique structure of the film, specifically the tilt in the GdYBCO lattice and the tilts in the extended (Y,Gd){sub 2}O{sub 3} and BaZrO{sub 3} nanoparticles. XRD and TEM were used to study the structure of the coated conductor. The effect of the misalignment between the external field H and the internal field B on the angular dependence of J{sub c} is discussed.

  5. Formation of Y{sub x}Nd{sub 1-x}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} (0{<=}x{<=}0.9) superconductors from an undercooled melt via aero-acoustic levitation

    Energy Technology Data Exchange (ETDEWEB)

    Gustafson, D.E.; Hofmeister, W.H.; Bayuzick, R.J.; Nagashio, K.; Kuribayashi, K

    2003-01-20

    This paper presents the results of rapid solidification experiments performed on the copper oxide superconductors Y{sub x}Nd{sub 1-x}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} (0{<=}x{<=}0.9). Spherical rare earth (RE) 123 specimens were levitated in O{sub 2} using aero-acoustic levitation (AAL), melted with a laser, undercooled, and solidified. The peritectic transformation temperature for the reaction RE{sub 2}BaCuO{sub 5}+liquid{yields}REBa{sub 2}Cu{sub 3}O{sub 7-{delta}} corresponding to the maximum recalescence temperature during solidification was determined. RE123 was formed directly from the melt for Y-Nd binary alloy compositions with Nd concentration greater than 20% (Y concentration less than 80%). A minimum in the peritectic transformation temperature for the Nd/Y123 system corresponding to a composition Y{sub 0.3}Nd{sub 0.7}123 was determined at 66 deg. C below the peritectic of pure Nd123.

  6. Magnetization and critical currents of Bi-Sr-Ca-Cu-O and Ba2YCu3O7 superconductors

    International Nuclear Information System (INIS)

    Gyorgy, E.M.; van Dover, R.B.; Jin, S.; Sherwood, R.C.; Schneemeyer, L.F.; Tiefel, T.H.; Waszczak, J.V.

    1988-01-01

    We have measured the critical currrent density J/sub c/ as a function of temperature for a Bi-Sr-Ca-Cu-O sample containing a substantial fraction of a phase with T/sub c/≅110 K and for a Ba 2 YCu 3 O 7 sample (TT/sub c/≅92 K). The behavior of J/sub c/ was deduced from magnetization measurements. For both samples the magnetization at fixed temperature and field decayed logarithmically with time. The values of J/sub c/ so derived, allowing for the decay to occur, went to zero for temperatures above 35 K for the Bi-Sr-Ca-Cu-O ceramic and to zero above 70 K for the Ba 2 YCu 3 O 7 sample. These values are substantially lower than those deduced from dynamic M-H loops

  7. Broad Temperature Pinning Study of 15 mol.% Zr-Added (Gd, Y)-Ba-Cu-O MOCVD Coated Conductors

    Energy Technology Data Exchange (ETDEWEB)

    Xu, AX; Khatri, N; Liu, YH; Majkic, G; Galstyan, E; Selvamanickam, V; Chen, YM; Lei, CH; Abraimov, D; Hu, XB; Jaroszynski, J; Larbalestier, D

    2015-06-01

    BaZrO3 (BZO) nanocolumns have long been shown to be very effective for raising the pinning force F-p of REBa2Cu3Ox (REBCO, where RE = rare earth) films at high temperatures and recently at low temperatures too. We have successfully incorporated a high density of BZO nanorods into metal organic chemical vapor deposited (MOCVD) REBCO coated conductors via Zr addition. We found that, compared to the 7.5% Zr-added coated conductor, dense BZO nanorod arrays in the 15% Zr-added conductor are effective over the whole temperature range from 77 K down to 4.2 K. We attribute the substantially enhanced J(c) at 30 K to the weak uncorrelated pinning as well as the strong correlated pinning. Meanwhile, by tripling the REBCO layer thickness to similar to 2.8 mu m, the engineering critical current density J(e) at 30 K exceeds J(e) of optimized Nb-Ti wires at 4.2 K.

  8. Oriented grained Y-Ba-Cu-O superconductors having high critical currents and method for producing same

    International Nuclear Information System (INIS)

    Salama, K.; Selvamanickam, V.

    1990-01-01

    This patent describes a process for preparing a superconducting metal oxide complex. It comprises: mixing solid compounds containing Y, Ba, Cu and O in amounts appropriate to yield the formula Y 1 Ba 2 Cu 3 O 6 + δ wherein δ has a number value of from about 0.1 to about 1.0; heating the solid compounds in air to a temperature between about 920 degrees C. to about 960 degrees C. for a time sufficient to react the compounds in the solid state quenching the solid state reaction product to ambient temperature in air; compacting the mixture into a solid mass; sintering the solid mass; heating the solid mass; rapidly cooling the mass to a temperature between about 1,020 degrees to about 1,040 degrees C. and then cooling the mass to a steady temperature between about 20 degrees C. to 40 degrees C. below its melting point at a rate of approximately 1 degrees C./hour; maintaining the mass at the steady temperature for a time sufficient for the entire mass to resolidify; cooling the resolidified mass in air from the steady temperature to approximately 550 degrees C. to 650 degrees C. at the rate of approximately 60 degrees C. per hour; additionally cooling the resolidified mass to about 380 degrees C. to about 420 degrees C. at the rate of approximately 30 degrees C. per hour in air; and annealing the resolidified mass

  9. Effects of calcium doping on the superconducting properties of top-seeded melt growth processed Y1.5Ba2-xCaxCu3Oy superconductors

    International Nuclear Information System (INIS)

    Park, S.D.; Kim, H.J.; Park, B.J.; Han, Y.H.; Jun, B.-H.; Lee, J.S.; Kim, C.-J.

    2011-01-01

    We study effects of calcium doping in melt processed Y123 superconductors. We examine a superconducting transition temperature and current density. A transition temperature and current density decreases by calcium doping. Calcium doping leads to coarseing of Y211 particles. Y211 refining effect by CeO 2 is disappreared by calcium doping. The effect of calcium doping on the superconducting properties of top seeded melt growth (TSMG) processed Y 1.5 Ba 2-x Ca x Cu 3 O y superconductors was studied in terms of calcium content (X ca ). YBa 2-x Ca x Cu 3 O 7-δ (X ca = 0, 0.005, 0.01, 0.02, 0.04, 0.1, 0.3) powders were synthesized by the powder calcination method. YBa 2-x Ca x Cu 3 O 7-δ powders were mixed with 0.25 mole Y 2 O 3 powder and 1 wt.% CeO 2 as Y 2 BaCuO 5 (Y211) refiner, and finally made into Y 1 . 5 Ba 2-x Ca x Cu 3 O y (Y1.5) + 1 wt.% CeO 2 composition. The single Y123 growth on the top surface was observed up to X ca = 0.1, while the multiple Y123 growth was observed at X ca ≥ 0.1. The superconducting transition temperature (T c ) and critical current density (J c ) of TSMG processed Y1.5 samples were inversely proportional to X ca . The Y211 size increased with increasing X ca due to the enhancement of Y211 coarsening by calcium doping. No Y211 refining effect by CeO 2 was observed in the calcium doped samples. The T c and J c decrease by calcium doping are likely to be due to the calcium incorporation with the Y123 lattice and formation of coarse Y211 particles.

  10. SmBaCoCuO5+x as cathode material based on GDC electrolyte for intermediate-temperature solid oxide fuel cells

    International Nuclear Information System (INIS)

    Lue Shiquan; Long, Guohui; Ji Yuan; Meng Xiangwei; Zhao Hongyuan; Sun Cuicui

    2011-01-01

    Research highlights: → We synthesize a new kind of layered perovskite SmBaCoCuO 5+x (SBCCO) as a cathode material of a solid oxide fuel cell. → There are some reports on the performance of cathodes in proton-conducting SOFCs based on BaCe 0.8 Sm 0.2 O 3-δ electrolyte. → However, to the best of our knowledge, the performance of SBCCO cathodes in oxygen-ion conducting SOFCs has not been reported to date. → In this work, the ceramic powder SBCCO is examined as a cathode for IT-SOFCs based on Ce 0.9 Gd 0.1 O 1.95 (GDC) electrolyte. - Abstract: The performance of SmBaCoCuO 5+x (SBCCO) cathode has been investigated for their potential utilization in intermediate-temperature solid oxide fuel cells (IT-SOFCs). The powder X-ray diffraction (XRD), thermal expansion and electrochemical performance on Ce 0.9 Gd 0.1 O 1.95 (GDC) electrolyte are evaluated. XRD results show that there is no chemical reaction between SBCCO cathode and GDC electrolyte when the temperature is below 950 o C. The thermal expansion coefficient (TEC) value of SBCCO is 15.53 x 10 -6 K -1 , which is ∼23% lower than the TEC of the SmBaCo 2 O 5+x (SBCO) sample. The electrochemical impedance spectra reveals that SBCCO symmetrical half-cells by sintering at 950 deg. C has the best electrochemical performance and the area specific resistance (ASR) of SBCCO cathode is as low as 0.086 Ω cm 2 at 800 o C. An electrolyte-supported fuel cell generates good performance with the maximum power density of 517 mW cm -2 at 800 deg. C in H 2 . Preliminary results indicate that SBCCO is promising as a cathode for IT-SOFCs.

  11. Effects of magnetic field on the cuprate high-Tc superconductor La2-xSrxCuO4

    DEFF Research Database (Denmark)

    Lake, B.; Aeppli, G.; Christensen, N.B.

    2004-01-01

    This article discusses neutron scattering measurements on the cuprate, high transition temperature superconductor La2-xSrxCuO4 (LSCO) in an applied magnetic field. LSCO is a type-II superconductor and magnetic flux can penetrate the material via the formation of vorticies. Phase coherent...

  12. Dopant structural distortions in high-temperature superconductors: an active or a passive role?

    International Nuclear Information System (INIS)

    Haskel, D.; Stern, E.A.; Dogan, F.; Moodenbaugh, A.R.

    2001-01-01

    The parent compounds of high-temperature superconductors, such as YBa 2 Cu 3 O 6 and La 2 CuO 4 , are strongly interacting electron systems, rendering them insulators with Mott-Hubbard gaps of a few electron volts. Charge carriers (holes) are introduced by chemical doping, causing an insulator-metal (IM) transition and, at low temperatures, superconductivity. The role of dopants is widely seen as limited to the introduction of holes into the CuO 2 planes (i.e. occupying electronic states derived from Cu 3d x2-y2 and O 2p x,y atomic orbitals). Most theories of high-T c superconductivity deal with pairing interactions between these planar holes. Local distortions around dopants are poorly understood, because of the experimental difficulty in obtaining such information, particularly at low doping. This has resulted in the neglect, in most theories, of the effect of such distortions on the chemical and electronic structure of high-T c superconductors. Angular-resolved X-ray absorption fine structure (XAFS) spectroscopy on oriented samples is an ideal technique to elucidate the dopant distortions. Element specificity, together with a large orientation dependence of the XAFS signal in these layered structures, allows the local structure around dopants to be resolved. Results are presented here on (Sr, Ba) and Ni dopants, which substitute at the La and Cu sites, respectively, of insulating La 2 CuO 4 . The relevance of the measured local distortions for a complete understanding of the normal and superconducting properties of cuprates is discussed. (au)

  13. Structural and superconducting properties of (Y,Gd)Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} grown by MOCVD on samarium zirconate buffered IBAD-MgO

    Energy Technology Data Exchange (ETDEWEB)

    Stan, L; Holesinger, T G; Maiorov, B; Feldmann, D M; Usov, I O; DePaula, R F; Civale, L; Foltyn, S R; Jia, Q X [Los Alamos National Laboratory, PO Box 1663, Los Alamos, NM 87545 (United States); Chen, Y; Selvamanickam, V [SuperPower, Incorporated, 450 Duane Avenue, Schenectady, NY 12304 (United States)

    2008-10-01

    Textured samarium zirconate (SZO) films have been grown by reactive cosputtering directly on an ion beam assisted deposited (IBAD) MgO template, without an intermediate homoepitaxial MgO layer. The subsequent growth of 0.9 {mu}m thick (Y,Gd)Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} ((Y, Gd)BCO) films by metal organic chemical vapor deposition (MOCVD) yielded well textured films with a full width at half maximum of 1.9{sup 0} and 3.4{sup 0} for the out-of-plane and in-plane texture, respectively. Microstructural characterizations of the SZO buffered samples revealed clean interfaces. This indicates that the SZO not only provides a diffusion barrier, but also functions as a buffer for (Y, Gd)BCO grown by MOCVD. The achievement of self-field critical current densities (J{sub c}) of over 2 MA cm{sup -2} at 75.5 K is another proof of the effectiveness of SZO as a buffer on the IBAD-MgO template. The in-field measurements revealed an asymmetric angular dependence of J{sub c} and a shift of the ab-plane maxima due to the tilted nature of the template and (Y,Gd){sub 2}O{sub 3} particles existing in the (Y, Gd)BCO matrix. The present results are especially important because they demonstrate that high temperature superconducting coated conductors with simpler architecture can be fabricated using commercially viable processes.

  14. Q factor of megahertz LC circuits based on thin films of YBaCuO high-temperature superconductor

    Science.gov (United States)

    Masterov, D. V.; Pavlov, S. A.; Parafin, A. E.

    2008-05-01

    High-frequency properties of resonant structures based on thin films of YBa2Cu3O7 δ high-temperature superconductor are studied experimentally in the frequency range 30 100 MHz. The structures planar induction coils with a self-capacitance fabricated on neodymium gallate and lanthanum aluminate substrates. The unloaded Q factor of the circuits exceeds 2 × 105 at 77 K and 40 MHz. Possible loss mechanisms that determine the Q factor of the superconducting resonant structures in the megahertz range are considered.

  15. High critical currents in Y-Ba-Cu-O superconductors

    International Nuclear Information System (INIS)

    Jin, S.; Tiefel, T.H.; Sherwood, R.C.; Davis, M.E.; van Dover, R.B.; Kammlott, G.W.; Fastnacht, R.A.; Keith, H.D.

    1988-01-01

    Melt-textured growth of polycrystalline YBa 2 Cu 3 O 7 √/sub δ/ superconductor using directional solidification created an essentially 100% dense structure consisting of long, needle- or plate-shaped crystals preferentially aligned parallel to the a-b conduction plane. The new microstructure, which completely replaces the previous granular and random structure in the sintered precursor, exhibits dramatically improved transport J/sub c/ values at 77 K of ∼17 000 Acm 2 in zero field and ∼4000 Acm 2 at H = 1 T (as compared to ∼500 and ∼1 Acm 2 , respectively, for the as-sintered structure), with the severe field dependence of J/sub c/ (''weak-link'' problem) no longer evident in the new melt-textured material. The improvement in J/sub c/ is attributed to the combined effects of densification, alignment of crystals, and formation of cleaner grain boundaries. Microstructure and distribution of various phases present in the melt-textured material are discussed in relation to the superconducting properties

  16. The high temperature resistivity of Ba2YCu3O7-chi

    International Nuclear Information System (INIS)

    Xingkui, Z.; Shining, Z.; Hao, W.; Shiyuan, Z.; Ningshen, Z.; Ziran, X.

    1988-01-01

    The high temperature resistivity (rho), thermogravimetry (TG) and derivative thermogravimetric (DTG) have been used to characterize superconductor Ba 2 YCu 3 O 7-chi (BYCO) in O 2 , air and N 2 . The resistivity is linear from room temperature at 350 0 C and then deviate from linearity with oxygen evolution, the derivative of resistivity drho/dT increases abruptly near orthorhombic to tetragonal phase transition. These phenomena can give good explanations for a two-band Drude model

  17. The High Temperature Resistivity of Ba2YCu3O7-x

    Science.gov (United States)

    Xingkui, Zhang; Shining, Zhu; Hao, Wang; Shiyuan, Zhang; Su, Ye; Ningshen, Zhou; Ziran, Xu

    The high temperature resistivity (ρ), thermogravimetry (TG) and derivative thermogravimetry (DTG) have been used to characterize superconductor Ba2YCu3O7-x (BYCO) in O2, air and N2. The resistivity is linear from room temperature to 350°C and then deviate from linearity with oxygen evolution, the derivative of resistivity dρ/dT increases abruptly near orthorhombic to tetragonal phase transition. These phenomena can give good explanations for a two-band Drude model.

  18. Transition conductivity study of high temperature superconductor compounds: the role of fluctuations

    International Nuclear Information System (INIS)

    Pagnon, V.

    1991-04-01

    This memory subject is the transition conductivity study of high temperature superconductors in corelation with their anisotropy. Systematic conductivity measurements were made on YBaCuO and BaSrCaCuO in relation with temperature from 4.2 K to 1200 K, and with a magnetic field up to 8 T in several directions. Oxygen order has an effect on the characteristics at YBaCuO transition conductivity. The activation energy for oxygen absorption is about 0.5eV. One method of analysis of the conductivity fluctuations about the transition temperature is proposed. Two separate rates are noticeable in YBaCuO compound. The 3 D fluctuations rate in the immediate neighbourghood of the transition lets place to the 2 D fluctuations rate at high temperature. Transitions temperatures governing each rate are different, that's incompatible with the formula proposed by Lawrence and Doniach. On the other hand, the analogy with quasi-2 D magnetic systems seems more relevant. A magnetic field application or a lowering of oxygen concentration removes the 3 D fluctuations rate. Non ohmic effects observed at the transition conductivity foot are analysis as a non-linear 2 D excitation manifestation of the supraconductive phase. Finally, by measurements on strontium doped YBaCuO crystals, we confirm a metal-insulator transition along the C-Axe when oxygen concentration reduces. This is connected with the specific heat jump. All these results uplighten the fundamental bidimensional character of high transition temperature superconductivity [fr

  19. Superconducting Dy1-x(Gd,Yb)xBa2Cu3O7-δ thin films made by Chemical Solution Deposition

    DEFF Research Database (Denmark)

    Opata, Yuri Aparecido; Wulff, Anders Christian; Hansen, Jørn Otto Bindslev

    2016-01-01

    Dy1-x(Gd or Yb)xBa2Cu3O7-δ samples were prepared using chemical solution deposition (CSD), based on trifluoroacetate metal-organic decomposition (MOD) methods. X-ray diffraction results demonstrated the formation of the RE123 superconducting phase with a strong in-plane and out-of-plane texture. c...

  20. Flux motion and dissipation in high-temperature superconductors

    International Nuclear Information System (INIS)

    Gray, K.E.; Kim, D.H.

    1991-08-01

    The effects on flux motion and dissipation of interlayer coupling of the Cu-O planes along the c-axis are considered for the high- temperature superconductors (HTS). It is argued that for the highly-anisotropic HTS, the weak interlayer coupling plays a dominant role that can be described by incoherent Josephson tunneling between superconducting Cu-O bi- or tri-layers. In YBa 2 Cu 3 O 7 , the layers are strongly coupled, presumably because the conducting Cu-O chains short circuit the Josephson tunneling, so that these effects are weak or missing

  1. Microstructural investigation of RBa/sub 2/Cu/sub 3/O/sub 7-delta/ (R=Y, Gd, Nd)

    Energy Technology Data Exchange (ETDEWEB)

    Parent, L; Moreau, C; Noel, D; Dallaire, S; Champagne, B

    1989-02-01

    RBa/sub 2/Cu/sub 3/O/sub 7-delta/ perovskites, where R is Y, Gd and Nd, were synthesized using the same experimental conditions. The resistivity curves of the three compounds were similar but their microstructures were different. Secondary phases (CuO, BaCuO/sub 2/) were formed in the compounds containing Y and Gd while no such phases were detected in the Nd perovskite material. 7 refs.; 4 figs.; 1 table.

  2. Flux pinning enhancement in thin films of Y3 Ba5 Cu8O18.5 + d

    Science.gov (United States)

    Aghabagheri, S.; Mohammadizadeh, M. R.; Kameli, P.; Salamati, H.

    2018-06-01

    YBa2Cu3O7 (Y123) and Y3Ba5Cu8O18 (Y358) thin films were deposited by pulsed laser deposition method. XRD analysis shows both films grow in c axis orientation. Resistivity versus temperature analysis shows superconducting transition temperature was about 91.2 K and 91.5 K and transition width for Y358 and Y123 films was about 0.6 K and 1.6 K, respectively. Analysis of the temperature dependence of the AC susceptibility near the transition temperature, employing Bean's critical state model, indicates that intergranular critical current density for Y358 films is more than twice of intergranular critical current density of Y123 films. Thus, flux pining is stronger in Y358 films. Weak links in the both samples is of superconductor-normal-superconductor (SNS) type irrespective of stoichiometry.

  3. Thermochemical properties of oxides in Y-Ba-Cu-O, Sr-Bi-O, Cu-Nb-O, Sr-Cu-O, Ca-Cu-O, Cu-O and Hg-Ba-Ca-Cu-O systems

    International Nuclear Information System (INIS)

    Moiseev, G.K.; Vatolin, N.A.; Il'inykh, N.I.

    2000-01-01

    Thermochemical properties (ΔH 0 298 , S 0 298 , H 0 298 -H 0 0 , C p (T), C p at T>T melt ) of complex oxides in Y-Ba-Cu-O, Sr-Bi-O, Cu-Nb-O, Sr-Cu-O, Ca-Cu-O, Cu-O and Hg-Ba-Ca-Cu-O systems obtained with application of calculation methods are presented. Nonexperimental methods of estimation, revision and correction of standard formation enthalpies of inorganic compounds are described [ru

  4. Contact spectroscopy of high-temperature superconductors (Review). I - Physical and methodological principles of the contact spectroscopy of high-temperature superconductors. Experimental results for La(2-x)Sr(x)CuO4 and their discussion

    Science.gov (United States)

    Ianson, I. K.

    1991-03-01

    Research in the field of high-temperature superconductors based on methods of tunneling and microcontact spectroscopy is reviewed in a systematic manner. The theoretical principles of the methods are presented, and various types of contacts are described and classified. Attention is given to deviations of the measured volt-ampere characteristics from those predicted by simple theoretical models and those observed for conventional superconductors. Results of measurements of the energy gap and fine structure of volt ampere characteristic derivatives are presented for La(2-x)Sr(x)CuO4.

  5. Effect of Barium-Precursors on Reaction Kinetics in Y-Ba-Cu-O System

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The reactions of stoichiometric Y2O3, CuO, and different Ba salts or oxides (BaCO3, Ba(NO3)2, BaO2, BaCuO2) for forming various compounds in the Y-Ba-Cu-O system (i.e., YBa2Cu3O7-δ, BaCuO2, Y2BaCuO5 and Y2Cu2O5) were systematically investigated by thermal analysis and X-ray diffractometry. The relevant activation energies were calculated from thermogravimetric data. It is found that the reaction pathway significantly depends on the thermal stability of the Ba precursors. Binary BaO-CuO phases form at low temperature (650~700 ℃) when in presence of easy-to-decompose Ba precursors, and then slowly transform to ternary compounds. On the contrary, when Ba ions are released at temperature higher than 900 ℃, ternary phases form directly from the components.

  6. Reversible axial-strain effect in Y-Ba-Cu-O coated conductors

    Energy Technology Data Exchange (ETDEWEB)

    Cheggour, N [National Institute of Standards and Technology, Boulder, CO 80305 (United States); Ekin, J W [National Institute of Standards and Technology, Boulder, CO 80305 (United States); Thieme, C L H [American Superconductor Corporation, Westborough, MA 01581 (United States); Xie, Y-Y [SuperPower Incorporated, Schenectady, NY 12304 (United States); Selvamanickam, V [SuperPower Incorporated, Schenectady, NY 12304 (United States); Feenstra, R [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

    2005-12-15

    The recently discovered reversible strain effect in Y-Ba-Cu-O (YBCO) coated conductors contrasts with the general understanding that the effect of strain on the critical-current density J{sub c} in practical high-temperature superconductors is determined only by crack formation in the ceramic component. Instead of having a constant J{sub c} as a function of strain before an irreversible drop when cracks form in the superconductor, J{sub c} in YBCO coated conductors can decrease or increase reversibly with strain over a significant strain range up to an irreversible strain limit. This reversible effect is present in samples fabricated either with rolling-assisted biaxially textured Ni-W substrates or with ion-beam-assisted deposition on Hastalloy substrates. The reversibility of J{sub c} with strain is observed for thin as well as thick YBCO films, and at two very different temperatures (76 and 4 K). The reversible effect is dependent on temperature and magnetic field, thus indicating its intrinsic nature. We also report an enhancement of the irreversible strain limit {epsilon}{sub irr} where the reversible strain effect ends and YBCO cracking starts. The value of {epsilon}{sub irr} increases from about 0.4% to more than 0.5% when YBCO coated conductors are fabricated with an additional Cu protection layer.

  7. Reversible axial-strain effect in Y-Ba-Cu-O coated conductors

    International Nuclear Information System (INIS)

    Cheggour, N; Ekin, J W; Thieme, C L H; Xie, Y-Y; Selvamanickam, V; Feenstra, R

    2005-01-01

    The recently discovered reversible strain effect in Y-Ba-Cu-O (YBCO) coated conductors contrasts with the general understanding that the effect of strain on the critical-current density J c in practical high-temperature superconductors is determined only by crack formation in the ceramic component. Instead of having a constant J c as a function of strain before an irreversible drop when cracks form in the superconductor, J c in YBCO coated conductors can decrease or increase reversibly with strain over a significant strain range up to an irreversible strain limit. This reversible effect is present in samples fabricated either with rolling-assisted biaxially textured Ni-W substrates or with ion-beam-assisted deposition on Hastalloy substrates. The reversibility of J c with strain is observed for thin as well as thick YBCO films, and at two very different temperatures (76 and 4 K). The reversible effect is dependent on temperature and magnetic field, thus indicating its intrinsic nature. We also report an enhancement of the irreversible strain limit ε irr where the reversible strain effect ends and YBCO cracking starts. The value of ε irr increases from about 0.4% to more than 0.5% when YBCO coated conductors are fabricated with an additional Cu protection layer

  8. Flux motion and dissipation in high-temperature superconductors

    International Nuclear Information System (INIS)

    Gray, K.E.; Kim, D.H.

    1991-01-01

    The effects on flux motion and dissipation of interlayer coupling of the Cu-O planes along the c-axis are considered for the high-temperature superconductors (HTS). It is argued that for the highly-anisotropic HTS, the weak interlayer coupling plays a dominant role that can be described by incoherent Josephson tunneling between superconducting Cu-O bi- or tri-layers. In YBa 2 Cu 3 O 7 , the layers are strongly coupled, presumably because the conducting Cu-O chains short circuit the Josephson tunneling, so that these effects are weak or missing. Recently, the effects of anisotropy and fluctuations on critical current densities, J c (T,H) and the field-induced broadening of resistivity transitions, ρ(T,H), have been studied in high-temperature superconductors (HTS). Although the broadening looks similar for the applied field, H, oriented either parallel to the superconducting Cu-O layers (H parallel ab) or parallel to the c-axis (H parallel c), its width and the detailed shape of ρ(T,H) are different. The explanations given in this paper for the highly anisotropic HTS differ in detail for the two cases, but have a crucial feature in common: they result from fluctuations affecting the Josephson coupling across the interlayer junctions

  9. Positron studies in as received and electron irradiated YBa2Cu3O6.9, DyBa2Cu3O6.9 and CaSr2Bi2Cu2O8-δ

    International Nuclear Information System (INIS)

    Moser, P.; Henry, J.Y.

    1988-01-01

    The temperature dependence of the positron annihilation parameters is measured between 77K and 300K in different oxide superconductors before and after electron irradiation. Before irradiation a reproducible behaviour is observed in YBa 2 Cu 3 O 6.9 and DyBa 2 Cu 3 O 6.9 : a maximum of the positron lifetime and Doppler broadening is found at 150K suggesting that positrons are trapped in a well defined charged defect identified as the [Cu(1),nO] polyvacancy, with n=1 or 2. After electron irradiation, an increase in positron lifetime is found, which disappears by annealing between 100K and 500K

  10. Syntheses and crystal structures of BaAgTbS{sub 3}, BaCuGdTe{sub 3}, BaCuTbTe{sub 3}, BaAgTbTe{sub 3}, and CsAgUTe{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Prakash, Jai; Beard, Jessica C.; Ibers, James A. [Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3113 (United States); Mesbah, Adel [Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3113 (United States); ICSM-UMR 5257 CNRS/CEA/UM2/ENSCM, Bat 426, BP 17171, 30207 Bagnols/Ceze (France)

    2015-06-15

    Five new quaternary chalcogenides of the 1113 family, namely BaAgTbS{sub 3}, BaCuGdTe{sub 3}, BaCuTbTe{sub 3}, BaAgTbTe{sub 3}, and CsAgUTe{sub 3}, were synthesized by the reactions of the elements at 1173-1273 K. For CsAgUTe{sub 3} CsCl flux was used. Their crystal structures were determined by single-crystal X-ray diffraction studies. The sulfide BaAgTbS{sub 3} crystallizes in the BaAgErS{sub 3} structure type in the monoclinic space group C{sup 3},{sub 2h}-C2/m, whereas the tellurides BaCuGdTe{sub 3}, BaCuTbTe{sub 3}, BaAgTbTe{sub 3}, and CsAgUTe{sub 3} crystallize in the KCuZrS{sub 3} structure type in the orthorhombic space group D{sup 1},{sub 2}{sup 7},{sub h}-Cmcm. The BaAgTbS{sub 3} structure consists of edge-sharing [TbS{sub 6}{sup 9-}] octahedra and [AgS{sub 5}{sup 9-}] trigonal pyramids. The connectivity of these polyhedra creates channels that are occupied by Ba atoms. The telluride structure features {sup 2}{sub ∞}[MLnTe{sub 3}{sup 2-}] layers for BaCuGdTe{sub 3}, BaCuTbTe{sub 3}, BaAgTbTe{sub 3}, and {sup 2}{sub ∞}[AgUTe{sub 3}{sup 1-}] layers for CsAgUTe{sub 3}. These layers comprise [MTe{sub 4}] tetrahedra and [LnTe{sub 6}] or [UTe{sub 6}] octahedra. Ba or Cs atoms separate these layers. As there are no short Q..Q (Q = S or Te) interactions these compounds achieve charge balance as Ba{sup 2+}M{sup +}Ln{sup 3+}(Q{sup 2-}){sub 3} (Q = S and Te) and Cs{sup +}Ag{sup +}U{sup 4+}(Te{sup 2-}){sub 3}. (Copyright copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Critical state in the Y-Ba-Cu-O ceramics

    International Nuclear Information System (INIS)

    Artemov, A.N.; Grishin, A.M.; Korenivskii, V.N.; Ulyanov, A.N.; Khokhlov, V.A.

    1990-01-01

    This paper reports on the temperature and field dependences of the Y-Ba-Cu-O ceramics susceptibility studied both experimentally and theoretically. These dependence have been used to reconstruct the temperature dependence of the critical current (j c (T) = j c (O)(1 - T/T c1 ) 3/2 , J c (O) = 340 A/cm 2 , T c1 = 94.6 K) and the distribution of the granules with respect to the superconducting transition temperature (with the maximum at T c2 = 95.3 K and ΔT = 1.1 K). Within the critical state concept diamagnetic response of the granular superconductors at fundamental and multiple frequencies has been calculated. The calculation results are in good agreement with the experimentally obtained susceptibility dependences and explain the different dependences of the diamagnetic response on the magnitude of the d.c. field and the amplitude of a.c. field

  12. Layered perovskite PrBa0.5Sr0.5CoCuO5+δ as a cathode for intermediate-temperature solid oxide fuel cells

    International Nuclear Information System (INIS)

    Wang, Biao; Long, Guohui; Ji, Yuan; Pang, Mingjun; Meng, Xiangwei

    2014-01-01

    Highlights: • A single-phase layered-perovskite PrBa 0.5 Sr 0.5 CoCuO 5+δ (PBSCCu) is prepared by the EDTA–citrate complexing method. • PBSCCu cathode has a good chemical compatible with GDC electrolyte. • Partial substitution of Cu for Co can efficiently lower the thermal expansion coefficient. • Performances of PrBa 0.5 Sr 0.5 CoCuO 5+δ cathode based on Gd 0.1 Ce 0.9 O 1.95 electrolyte is reported firstly. - Abstract: Layered perovskite PrBa 0.5 Sr 0.5 CoCuO 5+δ (PBSCCo) oxide is synthesized by EDTA–citrate complexing method and investigated as a novel cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs). X-ray diffraction results show that PBSCCo is chemical compatible with Gd 0.1 Ce 0.9 O 1.95 (GDC) electrolyte below 950 °C. The thermal expansion coefficient of PBSCCo is 17.58 × 10 −6 K −1 between 30 °C and 900 °C. The maximum electrical conductivity of PBSCCo is 483 S cm −1 at 325 °C. The polarization resistance of PBSCCo cathode on GDC electrolyte is as low as 0.06 Ω cm 2 at 800 °C. The maximum power density of the electrolyte-supported single cell with PBSCCo cathode achieves 521 mW cm −2 at 800 °C. Preliminary results indicate that PBSCCo is a potential cathode material for application in IT-SOFCs

  13. Defect chemistry of ''BaCuO2''. Pt. 1. Oxygen non-stoichiometry, cation molecularity and X-ray diffraction determinations

    International Nuclear Information System (INIS)

    Spinolo, G.; Consiglio Nazionale delle Ricerche, Pavia; Anselmi-Tamburini, U.; Consiglio Nazionale delle Ricerche, Pavia; Arimondi, M.; Consiglio Nazionale delle Ricerche, Pavia; Ghigna, P.; Consiglio Nazionale delle Ricerche, Pavia; Flor, G.; Consiglio Nazionale delle Ricerche, Pavia

    1995-01-01

    ''BaCuO 2 '' is the key intermediate in the synthesis of the Ba 2 YCu 3 O 7-δ superconductor. Its very complex crystal structure is able to accommodate a large change in oxygen content. Oxygen non-stoichiometry of ''BaCuO 2 '' materials with 1:1 and 88:90 (Ba:Cu) molecularity has been investigated by polythermal X-ray powder diffraction coupled with isobaric-isothermal gravimetry determinations under different temperature and oxygen partial pressure conditions [300 ≤ T ≤ 820 C, 1 ≥ P(O 2 ) ≥3 . 10 -3 atm]. The 1:1 composition does not give well reproducible results, thus suggesting its polyphasic nature, at least in part of the investigated range. The results for the 88:90 ≅ 0.98 (Ba:Cu) composition are well reproducible and show that the material is single phase. Ba 0.98 CuO 1.98 + δ is oxygen over-stoichiometric in the whole investigated [T, P(O 2 )] range, with a maximum value δ ∼ 0.21. A Rietveld X-ray profile fitting is in agreement with previous single-crystal data. The trend of δ vs. P(O 2 ) is consistent with the presence of oxygen interstitial defects on (possibly different) crystallographic sites. (orig.)

  14. Ferro-paramagnetic coupled resonant modes in GdEuCuO4

    International Nuclear Information System (INIS)

    Fainstein, A.; Tovar, M.

    1990-01-01

    Two paramagnetic resonances were observed in compound GdEuCuO 4 : one was originated in trivalent gadolinium paramagnetism, while the other is associated to a weak ferromagnetic mode in Cu-O planes. In this work, experimental results are presented that show an anisotropy and a strongly anomalous temperature dependence of Gd 3+ . A theoretical model was introduced which explains the data in terms of coupled ferro-paramagnetic resonant modes originated in spin exchange coupling of Cu and Gd. (Author). 9 refs., 4 figs

  15. Reversible and irreversible magnetocaloric effect in the NdBa{sub 2}Cu{sub 3}O{sub 7} superconductor in relation to specific heat and magnetization

    Energy Technology Data Exchange (ETDEWEB)

    Plackowski, T [Departement de Physique de la Matiere Condensee, Universite de Geneve, CH-1211 Geneva 4 (Switzerland); Institute of Low Temperature and Structure Research, ulica Okolna 2, 50-422 Wroclaw (Poland); Wang, Y [Departement de Physique de la Matiere Condensee, Universite de Geneve, CH-1211 Geneva 4 (Switzerland); Lortz, R [Departement de Physique de la Matiere Condensee, Universite de Geneve, CH-1211 Geneva 4 (Switzerland); Junod, A [Departement de Physique de la Matiere Condensee, Universite de Geneve, CH-1211 Geneva 4 (Switzerland); Wolf, Th [Forschungszentrum Karlsruhe, Institut fuer Technische Physik, Postfach 3640, D-76021Karlsruhe (Germany)

    2005-11-02

    A recently developed technique for measuring the isothermal magnetocaloric coefficient (M{sub T}) is applied to the study of a superconducting NdBa{sub 2}Cu{sub 3}O{sub 7} single crystal. Results are compared with magnetization (M) and specific heat (C). In the reversible region both C and M{sub T} follow the scaling law of the 3D-xy universality class. The anomalies connected with flux-line lattice melting are visible on M{sub T}(B) curves as peaks and steps, similar to C(T) curves yet with much smaller background. At lower temperature, in the irreversible region the M{sub T}(B) behaviour resembles more that of M(B), exhibiting the 'fishtail' effect. Our results confirm that the peculiarities of the phase diagram known from the high-temperature superconductor YBa{sub 2}Cu{sub 3}O{sub 7}, e.g. vortex melting, dominance of critical fluctuations and absence of a B{sub c2} critical field line, are a common property of RE-123 systems.

  16. Oxygen potentials and phase equilibria of the quaternary Y-Ba-Cu-O system in the region involving the YBa2Cu3O7-x phase

    International Nuclear Information System (INIS)

    Fitzner, K.; Musbah, O.; Hsieh Kerchang; Zhang Minxian; Chang, Y.A.

    1993-01-01

    The equilibrium oxygen potentials of four-phase equilibria (counting only the condensed phases) in the CuO-Cu 2 O-BaCuO 2 -Y 2 BaCuO 5 (211)-YBa 2 Cu 3 O 7-x (123) phase region were determined using the following solid-oxide electrolyte e.m.f. cell: Pt10Rh, air (psub(O 2 )=0.21 atm) vertical stroke ZrO 2 +Y 2 O 3 vertical stroke mixtures of oxides, Pt. The oxide mixtures whose oxygen potentials were measured were CuO-Cu 2 O-211-123, CuO-Cu 2 O-BaCuO 2 -123, Cu 2 O-BaCuO 2 -211-123 and CuO-BaCuO 2 -211-123. The phase in some of the mixtures were identified by X-ray diffraction. These data were analyzed and are presented using stability diagrams, i.e., oxygen potential as a function of the reciprocal of the temperature. Extrapolation of these data for the four four-phase equilibra to high temperatures yields a metastable five-phase equilibrium, i.e., 123=CuO+Cu 2 O+BaCuO 2 +211, at ∼1243 K (970 ) and log psub(O 2 ) ∼ -1.21 (psub(O 2 )∼0.062 atm). (orig.)

  17. Magnetic properties of Bi- and Tl- based new high-Tc superconductors

    International Nuclear Information System (INIS)

    Togano, K.; Kumakura, H.; Dietderich, D.H.

    1988-01-01

    Upper critical field H c2 and Magnetization curve were measured for new high-T c oxide superconductors of Bi-Sr-Ca-Cu-O and Tl-Ba-Ca-Cu-O systems. H c2 values at 77K for the high-T phase of Bi-Sr-Ca-Cu-O, low-T c (T c (ρ = 0) = 105K) phase of Tl-Ba-Ca-Cu-O, and high-T c (T c (ρ = 0)=115K) phase of Tl-Ba-Ca-Cu-O are 41T, 50T, and 100T, respectively. The magnetization curve of the Bi-Sr-Ca-Cu-O shows a relatively small hysterisis, suggesting a weak pinning force compared to Tl-Ba-Ca-Cu-O as well as Ba 2 YCU 3 O x . Critical current density J c of 600A/Cm 2 at 77K and zero-magnetiac field was attained for the high-T c sample of Tl-Ba-Ca-Cu-O

  18. Stability of Tl-Ba-Ca-Cu-O Superconducting Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Siegal, M.P.; Overmyer, D.L.; Venturini, E.L.; Padilla, R.R.; Provencio, P.N.

    1999-08-23

    We report the stability of TlBa{sub 2}CaCu{sub 2}O{sub 7} (Tl-1212) and Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8} (T1-2212) thin films and by inference, the stability of TlBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub 9} (Tl-1223) and Tl{sub 2}Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} (Tl-2223) thin films, under a variety of conditions. In general, we observe that the stability behavior of the single Tl-O layer materials (Tl-1212 and Tl-1223)are similar and the double Tl-O layer materials (Tl-2212 and Tl-2223) are similar. All films are stable with repeated thermal cycling to cryogenic temperatures. Films are also stable in acetone and methanol. Moisture degrades film quality rapidly, especially in the form of vapor. Tl-1212 is more sensitive to vapor than Tl-2212. These materials are stable to high temperatures in either N{sub 2}, similar to vacuum for the cuprates, and O{sub 2} ambients. While total degradation of properties (superconducting and structural) occur at the same temperatures for all phases, 600 C in N{sub 2} and 700 C in O{sub 2}, the onset of degradation occurs at somewhat lower temperatures for Tl-1212 than for Tl-2212 films. In all cases, sample degradation is associated with Tl depletion from the films.

  19. Contact spectroscopy of high-temperature superconductors. Review

    International Nuclear Information System (INIS)

    Yanson, I.K.

    1991-01-01

    We have attempted to systematize the research of high temperature superconductors by means of tunneling and point-contact spectroscopy. The theoretical grounds of the methods are briefly described. The deviations of current-voltage characteristics from ordinary superconductors are considered. The properties of point contacts with direct energy gap measurfements and the fine structure of derivatives of i(v) curves at the overlap energies are reviewed for the high-T c La 2-x Sr x CuO 4 materials

  20. New Phases of YBaCuGeO Superconductors Identified from X-ray Diffraction and Infra-red Absorption Measurements

    Science.gov (United States)

    Abo-Arais, Ahmed; Dawoud, Mohamad Ahmad Taher

    2005-01-01

    X-ray powder diffraction patterns and infra-red absorption spectra have been evaluated and analysed for the Y1 Ba2 Cu3 O7-d - Gex compound samples prepared by the solid state reaction with x values ranging from 0.0 to 1.13. All samples show bulk superconductivity above liquid nitrogen temperature using the levitation test (Meissner effect). Samples with Ge content up to x = 0.2 have offset Tc between 83K and 92K while the sample with x = 1.13 shows semiconducting behavior above 100K. As a result of the solid state interaction between YBCO and Ge, new phases are observed and determined, mainly three phases are concluded from X-ray powder diffraction analysis: (i) Ba2GeO4 (ii) Y2BaCuO5 (iii) BaCO3. The unit cell parameters a, b and c of the orthorhombic superconducting phase are calculated for all the prepared samples. The anisotropy factor is evaluated and related to the new structural phases in YBCO-Ge composite system. The I-R absorption spectra for the samples with orthorhombic symmetry have been determined. The phonon modes between ~ 400 cm-1 and 630 cm-1 are attributed to the Cu - O octahedron and pyramid vibrations for the CuO2 -planes and CuO-chains, while the peaks in the range from ~ 700 cm-1 to ~ 860 cm-1 may be due to defects such as the new phase Ba2GeO4 and the green phase Y2BaCuO5. The obtained results are discussed according to the superconductor - semi-conductor composite model and with the phonon-mediated charge transfer between CuO2 -planes and CuO- chains through apex oxygen (BaO).

  1. Synthesis, structural characterization and fluctuation conductivity of HoBa{sub 2}Cu{sub 3}O{sub 7-{delta}-}SrTiO{sub 3} composites

    Energy Technology Data Exchange (ETDEWEB)

    Uribe Laverde, M.A., E-mail: mauribel@bt.unal.edu.c [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, Bogota (Colombia); Landinez Tellez, D.A.; Roa-Rojas, J. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, Bogota (Colombia)

    2010-12-15

    Single-phase polycrystalline samples of HoBa{sub 2}Cu{sub 3}O{sub 7-{delta}} superconductor and SrTiO{sub 3} isolator were produced by means of the solid state reaction technique. After structural characterization of both materials, superconductor-isolator composites were produced with nominal isolator volume percentages between 0% and 10%. Resistivity measurements for the composites and the HoBa{sub 2}Cu{sub 3}O{sub 7-{delta}} sample with different currents evidenced a superconducting transition with critical temperature T{sub C} = 92 K, with wider transitions with increasing either isolator content or measurement current. Fluctuation conductivity analyses were carried out to obtain the exponents characterizing the conductivity divergence. Above T{sub C}, apart from the typical Gaussian and critical fluctuations an atypical regime with critical exponent about 0.14 is observed as a precursor of the transition. Below T{sub C}, it is observed that the coherence transition characteristic exponent increases rapidly with increasing isolator percentage in the composites and does not show important changes when modifying the current in the pure superconductor sample.

  2. Conductivity fluctuation in the high temperature superconductor with planar weight disparity Y{sub 0.5}Sm{sub 0.5}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Barrera, E.W.; Rojas Sarmiento, M.P.; Rincon, L.F.; Landinez Tellez, D.A.; Roa-Rojas, J. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, A.A. 14490, Bogota DC (Colombia)

    2007-07-01

    The synthesis of the Y{sub 0.5}Sm{sub 0.5}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} superconducting material by the standard solid state reaction is reported. DC resistivity measurements reveal the improvement of the critical temperature (T{sub c}) when substitution of exact 50-50 mix of Yttrium and Samarium is performed. A bulk T{sub c} = 101 K was determined by the criterion of the maximum in the temperature derivative of electrical resistivity. Structure characterization by means the x-ray diffraction technique shows the crystalline appropriated distribution of Yttrium and Samarium to create substantial planar weight disparity (PWD) in alternating layers. This PWD increases T{sub c} in copper-oxide superconductors. In order to examine the effect of PWD on the pairing mechanism close to T{sub c}, conductivity fluctuation analysis was performed by the method of logarithmic temperature derivative of the conductivity excess. We found the occurrence of Gaussian and genuinely critical fluctuations. Our results are in agreement with reports on YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}, but an enhancement of the Gaussian fluctuation regimes was experimentally detected as a result of the PWD. The correlations of the critical exponents with the dimensionality of the fluctuation system for each Gaussian regime were performed by using the Aslamazov-Larkin theory. The genuinely critical exponent is interpreted by the 3D-XY model as corresponding with the dynamical universality class of the E-model. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Deposition of superconducting (Cu, C)-Ba-O films by pulsed laser deposition at moderate temperature

    International Nuclear Information System (INIS)

    Yamamoto, Tetsuro; Kikunaga, Kazuya; Obara, Kozo; Terada, Norio; Kikuchi, Naoto; Tanaka, Yasumoto; Tokiwa, Kazuyasu; Watanabe, Tsuneo; Sundaresan, Athinarayanan; Shipra

    2007-01-01

    Superconducting (Cu, C)-Ba-O thin films have been epitaxially grown on (100) SrTiO 3 at a low growth temperature of 500-600 deg. C by pulsed laser deposition. The dependences of their crystallinity and transport properties on preparation conditions have been investigated in order to clarify the dominant parameters for carbon incorporation and the emergence of superconductivity. It has been revealed that the CO 3 content in the films increases with increasing both the parameters of partial pressure of CO 2 during film growth and those of growth rate and enhancement of superconducting properties. The present study has also revealed that the structural and superconducting properties of the (Cu, C)-Ba-O films are seriously deteriorated by the irradiation of energetic particles during deposition. Suppression of the radiation damage is another key for a high and uniform superconducting transition. By these optimizations, a superconducting onset temperature above 50 K and a zero-resistance temperature above 40 K have been realized

  4. High coercivity Gd-substituted Ba hexaferrites, prepared by chemical coprecipitation

    Science.gov (United States)

    Litsardakis, G.; Manolakis, I.; Serletis, C.; Efthimiadis, K. G.

    2008-04-01

    A series of Gd-substituted Ba hexaferrites with nominal formula (Ba1-xGdx)Oṡ5.25 Fe2O3 (x=0-0.30) were prepared by the chemical coprecipitation method from nitrate precursors and heating at T =800-1200°C for 2h. The samples have been examined by x-ray diffraction, vibrating-sample magnetometer, and scanning electron microscopy methods. Gd substituted samples form single phase materials with the M-type hexaferrite structure at all heating temperatures, in the range of x ⩽0.10-0.20. The saturation magnetization (at 1.8T) varies slightly with x in most cases and, for x =0.05-0.10, it increases up to 66.7Am2/kg, exceeding the value of the unsubstituted hexaferrite. A strong enhancement of the coercivity is observed for all substituted samples, with maximum values Hc=457kA/m for the single-phase x =0.10 sample annealed at 1000°C and Hc=477kA/m for the x =0.25 sample annealed at 1100°C which contains Fe2O3 and GdFeO3 impurities. As the variation of coercivity with either substitution rate (x ) or annealing temperature is not monotonic, three different factors may account for the high coercivities that are obtained: (a) an inhibition of grain growth due to the presence of Gd, (b) a possible inherent effect on magnetocrystalline anisotropy, especially for single phase samples, and (c) a microstructural effect of secondary phases.

  5. Junction structures based on the high-Tc superconductor YBa2Cu3O7-δ

    International Nuclear Information System (INIS)

    Gijs, M.A.M.

    1993-01-01

    An overview is given of the investigations of the Josephson effect in junction structures based on the high-T c superconductor YBa 2 Cu 3 O 7-δ , which were carried out at the Philips Research Laboratories in Eindhoven in the 1988-1990 period. The reported results are presented in their international scientific context, without attempting a complete review of the subject. However, the various junction types studied give a good idea of the scientific pursuits of high-T c junction researchers in this period. The following junctions are considered: in the category of 'weak link'-type junctions we have investigated YBa 2 Cu 3 O 7-δ -Ag-Nb point contact junctions, YBa 2 Cu 3 O 7-δ Dayem bridges and YBa 2 Cu 3 O 7-δ -Ag(-Al)-Pb proximity junctions. In these structures we combine a high-T c with a low-T c superconductor. We also fabricated planar 'all high-T c ' YBa 2 Cu 3 O 7-δ -Ag-YBa 2 Cu 3 O 7-δ junctions using a submicron structuring process. Next we have made tunnel junctions to study density of states effects of the high-T c superconductor : YBa 2 Cu 3 O 7-δ -Pb junctions using the degraded YBa 2 Cu 3 O 7-δ -Pb interface as a tunnel barrier, and YBa 2 Cu 3 O 7-δ -Ag-Al/Al 2 O 3 /Pb tunnel junctions based on the superconducting proximity effect. Our junction structures are electrically characterized and mostly studied in microwave and magnetic fields. Results are compared with current theoretical models. (orig.)

  6. XES studies of density of states of high temperature superconductors

    Science.gov (United States)

    Jasiolek, Gabriel

    1991-01-01

    X-ray emission spectroscopic studies concerning the superconducting crystals, thin films, and ceramics of the Y-Ba-Cu-O, Tm-Ba-Cu-O, Bi-Sr-Ca-Cu-O, Bi-Pb-Sr-Ca-Cu-O, and Tl-Ba-Ca-Cu-O types are presented. The contributions of the 13d(9)L, 13d(10)L, 13d(10)LL, and 13d(10)L(2) configurations, where L denotes a ligand hole at the oxygen orbitals in the spectroscopic pattern of these superconductors are discussed. An attempt to connect the x-ray 'as registered' Cu L(alpha) emission spectra with the density of states close to the Fermi level, considering an influence of the CuL3 absorption edge, is presented. The corrected intensity distributions below the Fermi level are found to correspond to the theoretical density of states. Furthermore, an approach to the average valence of copper basing on the account of the self-absorption and fluorescence effects and on the configurations listed above is shown. The average valence of copper in the materials investigated is estimated to lie in the range of +2.10 to 2.32 when the formal trivalent copper is considered as that characterized by the 13d(9)L configuration. The density of states at the Fermi level was estimated to be 2.4 states/eV-cell for a Bi-Sr-Ca-Cu-O crystal and 3.6 states/eV-cell for a Tl-Ba-Ca-CU-O ceramic.

  7. Transport properties of YBa2Cu3O7/PrBa2Cu3O7 superlattices

    International Nuclear Information System (INIS)

    Jakob, G.; Hahn, T.; Stoelzel, C.; Tome-Rosa, C.; Adrian, H.

    1992-01-01

    We investigated the transport properties of high-quality YBa 2 Cu 3 O 7 /PrBa 2 Cu 3 O 7 superlattices. The exceptional structural order of the superlattices resulted in satellite peaks up to the ninth order in X-ray diffraction diagrams and high Tc values. We find high superconducting critical transport current densities j c even for ultrafine modulated superlattices which proves the existence of nearly continuous YBa 2 Cu 3 O 7 layers. The activation energy U is found to be constant or to have a linear temperatures dependence over a wide temperature range. (orig.)

  8. Growth and structural characterization of single crystals of the magnetic superconductor Ru1-xSr2-yGd1+yCu2+xO8-δ (RuGd-1212) obtained by the partial melting technique

    Science.gov (United States)

    Yamaki, K.; Bamba, Y.; Mochiku, T.; Funahashi, S.; Matsushita, Y.; Irie, A.

    2018-05-01

    In this study, cubic single crystals of the magnetic superconductor Ru1-xSr2-yGd1+yCu2+xO8-δ (RuGd-1212) with typical dimensions of 100-150 μm in length were grown by the partial melting technique. Multiple 00l reflections were first observed by XRD measurements of the bulk RuGd-1212 single crystals. The resistivity of the obtained crystals was roughly estimated to be ∼24-80 mΩ cm and no superconducting transition was observed down to 4.2 K. From the XRD measurements and refinement of the crystal structure, it was apparent that the Ru and Sr sites of the single-crystal RuGd-1212 were partially substituted by Cu and Gd, respectively. Oxygen defects were found to be minor (δ ≈ 0.1). The lattice parameters a and c of the single crystals were found to be larger and smaller, respectively, than those of a polycrystalline sample.

  9. Tuning the electrical and optical properties of Gd_1_-_xCa_xBaCo_2O_5_+_δ (x = 0–0.5) using solar energy

    International Nuclear Information System (INIS)

    Lu, Yi; Zhang, Rong; Wei, Ling; Lu, Chunhua; Fang, Zhenggang; Ni, Yaru; Xu, Zhongzi; Tao, Shunyan

    2016-01-01

    This study reveals that the use of a Ca dopant can increase the solar absorption of GdBaCo_2O_5_+_δ, with an optimal composition of Gd_0_._8Ca_0_._2BaCo_2O_5 achieving 85% solar absorptance. Electrical conductivity measurements revealed that this composition allows for faster insulator-metal transition and higher conductivity, with the observed variation in conductivity with 0.8 W/cm"2 of solar illumination explained in terms of a first-order spin-state transition. Thermal radiation imaging confirmed that regions of different radiative temperature are related to a change in free carriers that promote scattering, and therefore, cause an increase in infrared reflection. This rapid electrical conductivity transition and the low infrared radiation properties at high temperatures strongly suggest that Gd_0_._8Ca_0_._2BaCo_2O_5 could be used in a variety of potential fields, such as high-temperature thermosensitive or thermal storage materials. - Highlights: • The solar absorption properties of GdBaCo_2O_5_+_δ can be improved by Ca doping. • Gd_0_._8Ca_0_._2BaCo_2O_5 shows ultrafast conductivity transition induced by solar energy. • Gd_0_._8Ca_0_._2BaCo_2O_5 exhibits low thermal radiative properties at high temperature.

  10. Investigation of the properties of carbon-base nanostructures doped YBa_2Cu_3O_7_−_δ high temperature superconductor

    International Nuclear Information System (INIS)

    Dadras, Sedigheh; Ghavamipour, Mahshid

    2016-01-01

    In this research, we have investigated the effects of three samples of carbon-base nanostructures (carbon nanoparticles, carbon nanotubes and silicon carbide nanoparticles) doping on the properties of Y_1Ba_2Cu_3O_7_−_δ (YBCO) high temperature superconductor. The pure and doped YBCO samples were synthesized by sol–gel method and characterized by resistivity versus temperature (ρ–T), current versus voltage (I–V), through X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis. The results confirmed that for all the samples, the orthorhombic phase of YBCO compound is formed. We found that the pinning energy and critical current density of samples increase by adding carbon nanostructures to YBCO compound. Also critical temperature is improved by adding carbon nanotubes to YBCO compound, while it does not change much for carbon and silicon carbide nanoparticles doped compounds. Furthermore, the samples were characterized by UV–vis spectroscopy in 300 K and the band gap of the samples was determined. We found that the carbon nanotubes doping decreases YBCO band gap in normal state from 1.90 eV to 1.68 eV, while carbon and SiC nanoparticles doping increases it to 2.20 and 3.37 eV respectively.

  11. Charge ordering transition in GdBaCo2O5: Evidence of reentrant behavior

    Science.gov (United States)

    Allieta, M.; Scavini, M.; Lo Presti, L.; Coduri, M.; Loconte, L.; Cappelli, S.; Oliva, C.; Ghigna, P.; Pattison, P.; Scagnoli, V.

    2013-12-01

    We present a detailed study on the charge ordering transition in a GdBaCo2O5.0 system by combining high-resolution synchrotron powder/single-crystal diffraction with electron paramagnetic resonance experiments as a function of temperature. We found a second-order structural phase transition at TCO = 247 K (Pmmm to Pmma) associated with the onset of long-range charge ordering. At Tmin ≈ 1.2TCO, the electron paramagnetic resonance linewidth rapidly broadens, providing evidence of antiferromagnetic spin fluctuations. This likely indicates that, analogously to manganites, the long-range antiferromagnetic order in GdBaCo2O5.0 sets in at ≈TCO. Pair distribution function analysis of diffraction data revealed signatures of structural inhomogeneities at low temperature. By comparing the average and local bond valences, we found that above TCO the local structure is consistent with a fully random occupation of Co2+ and Co3+ in a 1:1 ratio and with a complete charge ordering below TCO. Below T ≈ 100 K the charge localization is partially melted at the local scale, suggesting a reentrant behavior of charge ordering. This result is supported by the weakening of superstructure reflections and the temperature evolution of electron paramagnetic resonance linewidth that is consistent with paramagnetic reentrant behavior reported in the GdBaCo2O5.5 parent compound.

  12. Macroscopic phase separation in high-temperature superconductors

    Science.gov (United States)

    Wen, Hai-Hu

    2000-01-01

    High-temperature superconductivity is recovered by introducing extra holes to the Cu-O planes, which initially are insulating with antiferromagnetism. In this paper I present data to show the macroscopic electronic phase separation that is caused by either mobile doping or electronic instability in the overdoped region. My results clearly demonstrate that the electronic inhomogeneity is probably a general feature of high-temperature superconductors. PMID:11027323

  13. Evaluation of oxygenation time in SmBa2Cu3O7-δ superconductors ceramics in air and ozone atmospheres

    International Nuclear Information System (INIS)

    Viana, P.R.P; Cunha, A.G.

    2010-01-01

    High temperature superconductors (HTSC) represent a major milestone in science. During the preparation of superconductors, oxygenation plays a key role, because oxygenation determines the distribution of charge carriers in these plans through the superconducting Cu-O and hence superconductivity. This paper proposes the preparation of polycrystalline superconductors using the ceramic method, and the step of oxygenation made with ozone gas (O 3 ). Ozone exerts chemical pressure on the compound, which has oxygen vacancies in its structure after the step of synthesis. The work was performed by varying the time between oxygenation 20, 40, 80 and 160 hours, with samples going through a process of oxygenation at 350 deg C after the step of synthesis. This study evaluates the time effect as oxygen can improve the superconducting properties such as resistivity and magnetic susceptibility. (author)

  14. About the role of silver in high temperature reactions of Y1 Ba2 Cu3 O7-σ superconductor ceramic

    International Nuclear Information System (INIS)

    Fiscina, J.E.; Esparza, D.A.

    1995-01-01

    Superconducting properties vs. firing protocol was studied in Ag-Y 1 Ba 2 Cu 3 O 7-σ composite. We present, as a part of a more complete study, R vs. T characterization. DTA-TGA measurements and SEM-EDAX analysis

  15. XRD spectra of new YBaCuO superconductors

    Indian Academy of Sciences (India)

    superconductors of YBaCuO materials by solid state reac- tion. They used the ... The XRD spectra and critical temperatures are shown to be the same as that of ... samples were synthesized by solid state reaction using raw materials Y2O3 ...

  16. Proximity-coupled CuO2 planes in high-Tc superconductors: evidence from pressure experiments up to 34 GPa on Y2Ba4Cu7O15.32

    International Nuclear Information System (INIS)

    Eenige, E.N. van; Griessen, R.; Heeck, K.; Schnack, H.G.; Wijngaarden, R.J.; Genoud, J.Y.; Graf, T.; Junod, A.; Muller, J.

    1992-01-01

    The Tc of superconducting Y 2 Ba 4 Cu 7 O 15.32 is measured up to a pressure of 33.7 GPa. After an initial increase from 95 K to 101.7 K a decrease down to 26.6 K is found, with a clear kink at 22 GPa. We demonstrate that Y 2 Ba 4 Cu 7 O 15.32 behaves as a multilayer of YBa 2 Cu 3 O 7 and YBa 2 Cu 4 O 8 building blocks coupled via the proximity effect. These data are not consistent with the idea that the coupling of two adjacent CuO 2 planes is necessary for superconductivity. (orig.)

  17. Three-dimensionality of field-induced magnetism in a high-temperature superconductor

    DEFF Research Database (Denmark)

    Lake, B.; Lefmann, K.; Christensen, N.B.

    2005-01-01

    Many physical properties of high-temperature superconductors are two-dimensional phenomena derived from their square-planar CuO(2) building blocks. This is especially true of the magnetism from the copper ions. As mobile charge carriers enter the CuO(2) layers, the antiferromagnetism of the parent...

  18. Microstructural investigation of RBa/sub 2/Cu/sub 3/O/sub 7/-delta (R=Y, Gd, Nd)

    Energy Technology Data Exchange (ETDEWEB)

    Parent, L; Moreau, C; Noel, D; Dallaire, S; Champagne, B

    1989-01-01

    RBa/sub 2/Cu/sub 3/O/sub 7-delta/ perovskites, where R is Y, Gd and Nd, were synthetized using the same experimental conditions. The resistivity curves of the three compounds were similar but their microstructures were different. Secondary phases (CuO, BaCuO/sub 2/) were formed in the compounds containing Y and Gd while no such phases were detected in the Nd perovskite material. According to these preliminary results, the perovskite containing Nd is readily synthesized since the amount of secondary phases is much lower in that case. 7 refs., 4 figs., 1 tab.

  19. Temperature dependence of the phonon structure in the high-temperature superconductor Bi2Sr2CaCu2O8 studied by infrared reflectance spectroscopy

    International Nuclear Information System (INIS)

    Kamaras, K.; Herr, S.L.; Porter, C.D.; Tanner, D.B.; Etemad, S.; Tarascon, J.

    1991-01-01

    We have investigated a ceramic sample of the high-temperature superconductor Bi 2 Sr 2 CaCu 2 O 8 (T c =85 K) by infrared and visible reflectance spectroscopy at several temperatures both below and above the superconducting transition. We find that the temperature variation in the vibrational region is associated with minima or antiresonance features of the optical conductivity, instead of maxima, indicating strong Fano-type electron-phonon interaction and implying that the phonon structure in the infrared is strongly affected by the ab-plane response

  20. Positron Annihilation Studies of the Electronic Structure of Selected High-Temperature Cuprate and Organic Superconductors.

    Science.gov (United States)

    Chan, Lie Ping

    The understanding of the electronic structure of the high-T_{c} superconductors could be important for a full theoretical description of the mechanism behind superconductivity in these materials. In this thesis, we present our measurements of the positron -electron momentum distributions of the cuprate superconductors Bi_2Sr_2CaCu _2O_8, Tl _2Ba_2Ca _2Cu_3O_ {10}, and the organic superconductor kappa-(BEDT)_2Cu(NCS) _2. We use the positron Two-dimensional Angular Correlation of Annihilation Radiation technique to make the measurements on single crystals and compare our high-statistics data with band structure calculations to determine the existence and nature of the respective Fermi surfaces. The spectra from unannealed Bi _2Sr_2CaCu _2O_8 exhibit effects of the superlattice modulation in the BiO_2 layers, and a theoretical understanding of the modulation effects on the electronic band structure is required to interpret these spectra. Since the present theory does not consider the modulation, we have developed a technique to remove the modulation effects from our spectra, and the resultant data when compared with the positron -electron momentum distribution calculation, yield features consistent with the predicted CuO_2 and BiO_2 Fermi surfaces. In the data from unannealed Tl_2Ba _2Ca_2Cu_3 O_{10}, we only observe indications of the TlO Fermi surfaces, and attribute the absence of the predicted CuO_2 Fermi surfaces to the poor sample quality. In the absence of positron-electron momentum calculations for kappa-(BEDT)_2Cu(NCS) _2, we compare our data to electronic band structure calculations, and observed features suggestive of the predicted Fermi surface contributions from the BEDT cation layers. A complete positron-electron calculation for kappa-(BEDT)_2 Cu(NCS)_2 is required to understand the positron wavefunction effects in this material.

  1. Phase compatibilities of YBa2Cu3O(9-delta) type structure in quintenary systems Y-Ba-Cu-O-X (impurity)

    Science.gov (United States)

    Karen, P.; Fjellvag, H.; Kjekshus, A.

    1990-01-01

    Electrical transport properties of the oxidic high T(sub c) superconductors are significantly affected by the presence of minor amounts of various elements adventing as impurities, e.g., from the chemical environment during manufacturing. YBa2Cu3O(9-delta) is prone to an extinction of the superconductivity on (partial) substitution of all four elemental components. E.g., Pr (for Y), La (for Ba), Zn (for Cu) or peroxygroup (for O) substituents will alter some of the superconductivity preconditions, like mixed valence state in Cu3O7/O(9-delta) network or structural distortion of the network. Although various pseudoternary chemical equilibrium phase diagrams of the Y(O)-Ba(O)-Cu(O) system now are available, no consensus is generally shown, however, this is partly due to lack of compatible definitions of the equilibrium conditions. Less information is available about the phase compatibilities in the appropriate quaternary phase diagram (including oxygen) and virtually no information exists about any pentenary phase diagrams (including one impurity). Unfortunately, complexity of such systems, stemming both from number of quaternary or pentenary compounds and from visualizing the five-component phase system, limits this presentation to more or less close surroundings of the YBa2Cu3O(9-delta) type phase in appropriate pseudoquaternary or pseudopseudoternary diagrams, involving Y-Ba-Cu and O, O-CO2, alkaline metals, Mg and alkaline earths, and Sc and most of the 3-d and 4-f elements. The systems were investigated by means of x ray diffraction, neutron diffraction and chemical analytical methods on samples prepared by sol-gel technique from citrates. The superconductivity was characterized by measuring the diamagnetic susceptibility by SQUID.

  2. Synthesis and properties of Tl endash Ba endash Ca endash Cu endash O superconductors

    International Nuclear Information System (INIS)

    Siegal, M.P.; Venturini, E.L.; Morosin, B.; Aselage, T.L.

    1997-01-01

    We review the synthesis methods and properties of single crystal, powder and thin film TlBaCaCuO high-temperature superconducting (Tl-HTS) materials. With transition temperatures ≥100K for several compounds, Tl-HTS materials present real opportunities for applications above 77 K. Experiments using (1) single crystals: determined precise structural parameters and identified the complex Tl 1+ -Tl 3+ equilibrium model; (2) powders: studied the complex thermodynamic phase diagram; and (3) epitaxial films: have studied fundamental properties such as electron pair symmetry and the effect of controlled extrinsic defects on flux pinning strength, as well as providing the large-area surfaces required for device applications. copyright 1997 Materials Research Society

  3. Synthesis and Structural Study of Sr2CuO3+δ Superconductor under High Pressure

    International Nuclear Information System (INIS)

    Qing-Qing, Liu; Fu-Ren, Wang; Feng-Ying, Li; Liang-Chen, Chen; Ri-Cheng, Yu; Chang-Qing, Jin; Yan-Chun, Li; Jing, Liu

    2008-01-01

    A single-phase Sr 2 CuO 3+δ superconductor is synthesized under high temperature and high pressure, in which oxygen atoms only partially occupy the apical sites next to the CuO 2 planes and act as hole-dopants. The superconducting transition temperature with T c max = 75 K is achieved in the material. Structure analysis from x-ray powder diffraction data show that this material crystallizes into a K 2 NiF 4 structure with tetragonal unit cell of a = 3. 795(3) Å and c = 12. 507(1) Å. Energy-dispersive synchrotron x-ray-diffraction studies at ambient are performed on powder samples of Sr 2 CuO 3+δ in a diamond-anvil cell at pressure up to 35 GPa. Anisotropic compressibility is found. Pressure-induced isostructural phase transition might exist as revealed by the discontinuous change of crystal cell volume V with pressure. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  4. High pressure study of high-temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Souliou, Sofia-Michaela

    2014-09-29

    The current thesis studies experimentally the effect of high external pressure on high-T{sub c} superconductors. The structure and lattice dynamics of several members of the high-T{sub c} cuprate and Fe-based superconductors families were investigated by means of Raman spectroscopy and X-ray diffraction under well-controlled, hydrostatic high pressure and low temperature conditions. The lattice dynamics of the high-T{sub c} superconductor YBa{sub 2}Cu{sub 3}O{sub 6+x} have been investigated systematically by Raman spectroscopy as a function of doping (x = 0.95, 0.75, 0.60, 0.55, and 0.45) and external pressure. Under ambient pressure conditions, in addition to the Raman modes expected from group theory, we observe new Raman active phonons upon cooling the underdoped samples, at temperatures well above the superconducting transition temperature. The doping dependence and the onset temperatures of the new Raman features suggest that they are associated with the incommensurate charge density wave (CDW) state recently discovered in underdoped cuprates using synchrotron X-ray scattering techniques. Under high pressure conditions (from 2 to 12 GPa), our Raman measurements on highly ordered underdoped YBa{sub 2}Cu{sub 3}O{sub 6.55} samples do not show any of the new Raman phonons seen at ambient pressure. High pressure and low temperature Raman measurements have been performed on the underdoped superconductor YBa{sub 2}Cu{sub 4}O{sub 8}. A clear renormalization of some of the Raman phonons is seen below T{sub c} as a result of the changes in the phonon self-energy upon the opening of the superconducting gap, with the most prominent one being that of the B{sub 1g}-like buckling phonon mode. The amplitude of this renormalization strongly increases with pressure, resembling the effect of hole doping in YBa{sub 2}Cu{sub 3}O{sub 6+x}. At ∝ 10 GPa, the system undergoes a reversible pressure-induced structural phase transition to a non-centrosymmmetric structure (space group

  5. High pressure study of high-temperature superconductors

    International Nuclear Information System (INIS)

    Souliou, Sofia-Michaela

    2014-01-01

    The current thesis studies experimentally the effect of high external pressure on high-T c superconductors. The structure and lattice dynamics of several members of the high-T c cuprate and Fe-based superconductors families were investigated by means of Raman spectroscopy and X-ray diffraction under well-controlled, hydrostatic high pressure and low temperature conditions. The lattice dynamics of the high-T c superconductor YBa 2 Cu 3 O 6+x have been investigated systematically by Raman spectroscopy as a function of doping (x = 0.95, 0.75, 0.60, 0.55, and 0.45) and external pressure. Under ambient pressure conditions, in addition to the Raman modes expected from group theory, we observe new Raman active phonons upon cooling the underdoped samples, at temperatures well above the superconducting transition temperature. The doping dependence and the onset temperatures of the new Raman features suggest that they are associated with the incommensurate charge density wave (CDW) state recently discovered in underdoped cuprates using synchrotron X-ray scattering techniques. Under high pressure conditions (from 2 to 12 GPa), our Raman measurements on highly ordered underdoped YBa 2 Cu 3 O 6.55 samples do not show any of the new Raman phonons seen at ambient pressure. High pressure and low temperature Raman measurements have been performed on the underdoped superconductor YBa 2 Cu 4 O 8 . A clear renormalization of some of the Raman phonons is seen below T c as a result of the changes in the phonon self-energy upon the opening of the superconducting gap, with the most prominent one being that of the B 1g -like buckling phonon mode. The amplitude of this renormalization strongly increases with pressure, resembling the effect of hole doping in YBa 2 Cu 3 O 6+x . At ∝ 10 GPa, the system undergoes a reversible pressure-induced structural phase transition to a non-centrosymmmetric structure (space group Imm2). The structural transition is clearly reflected in the high pressure

  6. Magneto-transport properties of Co3O4 nanoparticles added (Cu0.5Tl0.5)Ba2Ca2Cu3O10-δ superconducting phase

    Science.gov (United States)

    Mumtaz, M.; Baig, Mirza Hassan; Waqee-ur-Rehman, M.; Nasir Khan, M.

    2018-05-01

    Solid-state reaction method was used to synthesize Cu0.5Tl0.5Ba2Ca2Cu3O10-δ (CuTl-1223) superconducting phase and sol-gel method was used to prepare cobalt oxide (Co3O4) magnetic nanoparticles. These Co3O4 nanoparticles were added in CuTl-1223 superconducting matrix to get (Co3O4)x/CuTl-1223; x = 0-2.00 wt.% nanoparticles-superconductor composites. The effects of Co3O4 nanoparticles on crystal structure, phase formation, phase purity and infield superconducting transport properties of CuTl-1223 phase were investigated at different operating temperatures and external applied magnetic fields. The crystal structure and phase formation of Co3O4 nanoparticles and CuTl-1223 superconductor were determined by X-ray diffraction (XRD) technique. XRD peaks of Co3O4 nanoparticles were well indexed according to FCC crystal structure and the average particle size of 70 nm was calculated by using Debye-Scherer's formula. The unaltered crystal structure of host CuTl-1223 superconducting phase (i.e. Tetragonal) with the addition of Co3O4 nanoparticles indicated the dispersion of nanoparticles at inter-granular sites. Temperature dependent magneto-transport superconducting properties of (Co3O4)x/CuTl-1223 composites were investigated by zero field cooled (ZFC) and field cooled (FC) magnetic moment versus temperature (M-T) measurements. The onset transition temperatures {TcOnset (K)} was decreased along with the suppression of diamagnetic amplitude of CuTl-1223 superconducting phase with the addition of magnetic Co3O4 nanoparticles. Temperature dependent magnetic hysteresis (M-H loops) measurements of (Co3O4)x/CuTl-1223 composites were carried out at different operating temperatures from 5 K to 150 K. Critical current density (Jc) was calculated from M-H loops measurements by using Bean's model. Like the suppression of TcOnset (K) values, Jc was also decreased with the inclusion of Co3O4 nanoparticles. It was also observed that variation of Jc with H followed the power law Jc =

  7. Superconductivity and ceramic superconductors II; Proceedings of the Symposium, Orlando, FL, Nov. 12-15, 1990. Ceramic transactions. Vol. 18

    International Nuclear Information System (INIS)

    Nair, K.M.; Balachandran, U.; Chiang, Y.-M.; Bhalla, A.S.

    1991-01-01

    The present symposium on superconductivity and ceramic superconductors discusses fundamentals and general principles, powder processing and properties, fabrication and properties, and device reliability and applications. Attention is given to phase formation in the Tl-Ca-Ba-Cu-O system, comparative defect studies in La2CuO4 and La2NiO4, solid solution and defect behavior in high Tc oxides, oxygen ion transport and disorder in cuprates, and Sr-free Bi-Ln-Ca-Cu-O superconductors. Topics addressed include the preparation of superconductor Y-Ba-Cu-O powder by single-step calcining in air, low-temperature synthesis of YBa2Cu3O(7-x), synthesis of high-phase purity ceramic oxide superconductors by the xerogel method, and the preparation and characterization of the BYa2Cu4O8 superconductor. Also discussed are optical studies of humidity-based corrosion effects on thin film and bulk ceramic YBa2Cu3O(7-delta), thermomechanical processing of YBa2Cu3O(x)/Ag sheathed wires, and the expansion of high-Tc superconducting ceramics

  8. Physics and Materials Science of High Temperature Superconductors

    Science.gov (United States)

    1989-08-26

    30 M. Nikolo: Effect of Texture and Density on Grain Coupling of Sintered Y-Ba-Cu-O Superconductors 11:30 - 12:00 A. SzAsz : The Symmetries and High...The Hall coefficient is always positive and obeys the RH (x T- 1 law . The I Hall mobility p2-I2 < I cm2/V.S. At T < Tc, the thermoelectric power equals...461561 80-6550 Prof. A. Szasz PP Dr. Martin Schwarz PP Eotvos University Angewandte Physik Muzeum Krt. 6-8 Hoechst AG H-1088 Budapest Hungary Gebaeude

  9. An explanation of the irreversibility behavior in the highly- anisotropic high-temperature superconductors

    International Nuclear Information System (INIS)

    Gray, K.E.; Kim, D.H.

    1991-01-01

    The wide temperature range of the reversible, lossy state of the new high-temperature superconductors in a magnetic field was recognized soon after their discovery. This behavior, which had gone virtually undetected in conventional superconductors, has generated considerable interest, both for a fundamental understanding of the HTS and because it degrades the performance of HTS for finite-field applications. We show that recently proposed explanation of this behavior for the highly-anisotropic high-temperature superconductors, as a dimensional crossover of the magnetic vortices, is strongly supported by recent experiments on a Bi 2 Sr 2 CaCu 2 O x single crystal using the high-Q mechanical oscillator techniques

  10. Quantum vortex motion in high-Tc superconductors

    International Nuclear Information System (INIS)

    Garcia, A.; Zhang, X.X.; Tejada, J.

    1996-01-01

    Magnetic relaxation experiments at low temperatures were performed in different zero-field-cooled (ZFC) and field-cooled (FC) high-T c superconductors (HTSCs): TlBaCaCuO (2212 and 2223 phases, polycrystalline and thin-film samples), (Hg,Tl)BaCaCuO (1223 phase, polycrystalline material), and (Bi,Pb)SrCaCuO (2212 phase, single crystal). For each system and in the whole temperature range investigated, the relaxation curves obtained after both cooling processes are linear with the logarithm of time. The temperature dependence of the relaxation rate normalized to the first magnetization value, R=parallel d(M/M 0 )/dln(t)parallel, follows a trend which is common to all systems: R decreases linearly with decreasing temperature down to a value, which is called the crossover temperature, below which it levels off to a T-independent plateau. This behavior gives evidence of a transition in the mechanism responsible for the relaxation process at low temperatures, from thermally activated (linear dependence on T) to quantum vortex motion (T-independent regime). The experimental values for the crossover temperatures and normalized relaxation rates compare fairly well to numerical estimates in the framework of the theories of quantum vortex motion in layered HTSCs. Finally, the transition from one regime into another was studied in two samples of the TlBaCaCuO, 2223 phase, system in order to investigate the influence of dissipation on the quantum process. A clear conclusion on this point could not be drawn from these kinds of measurements. copyright 1996 American Institute of Physics

  11. X-ray photoelectron spectroscopy of high-temperature superconductor clean surfaces and interfaces

    International Nuclear Information System (INIS)

    Hill, D.M.

    1989-01-01

    X-ray photoelectron spectroscopy was used to determine the characteristic spectra for the high temperature superconductors La 1.85 Sr 0.15 CuO 4 , YBa 2 Cu 3 O 7-x , and Bi 2 Sr 2-x Ca 1+x Cu 2 O 8+y and their impurity phases. The oxidation state of Cu in all of these materials was predominantly Cu 2+ . The O 1s emission for clean surfaces was a single broad peak near 529 eV derived from emission from inequivalent O sites in the superconductors. The valence bands were a -6 eV wide manifold of Cu 3d-O 2p hybrid bands in the ∼ 1-7 eV binding energy range, with very low emission at E F arising from antibonding Cu 3d-O 2p orbitals. Emission from grain boundary and other impurity phases appeared at 531 eV for the O 1s core level, and in general ∼ 1-2 eV higher energy than the superconductor peak for other core levels except for Cu 2p. Impurity phases appeared in the valence bands as a shoulder at ∼ 5 eV. The amount of impurities detected was shown to be dependent on the fracture properties of the superconductors. All of the materials were shown to be stable under vacuum. The products and spatial extent of chemical reactions with Ag, Al, Al oxide, Au, Bi, Bi oxide, CaF 2 , Cu, Fe, Si, and Si oxide overlayers on these materials also were examined. Au, CaF 2 , and metal oxides deposited by activated oxidation during evaporation were non-reactive and non-disruptive of the superconductor surfaces. Ag overlayers were unique in that they disrupted the superconductor during deposition, but exhibited no evidence of any chemical reactions. Overlayers with an affinity for oxygen withdrew O from the superconductor. The O loss occurred preferentially from Cu atoms in the superconductor and disrupted the planar bonding structure

  12. Five-fold way to new high Tc superconductors

    Indian Academy of Sciences (India)

    Discovery of high c superconductivity in La2−BaCuO4 by Bednorz and Muller in 1986 was a breakthrough in the 75-year long search for new superconductors. Since then new high c superconductors, not involving copper, have also been discovered. Superconductivity in cuprates also inspired resonating valence ...

  13. Ba{sub y}Sr{sub 1−y}TiO{sub 3} buffer layers for strain tuning of infinite-layer Sr{sub 1−x}La{sub x}CuO{sub 2} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Sakuma, Keita, E-mail: sakuma.keita@d.mbox.nagoya-u.ac.jp; Ito, Masataka; He, Yilun; Hajiri, Tetsuya; Ueda, Kenji; Asano, Hidefumi

    2016-08-01

    We report on the precise tuning of lattice strain in an infinite-layer electron-doped high temperature superconductor Sr{sub 1−x}La{sub x}CuO{sub 2} (SLCO; a{sub SLCO} = 0.3949 nm for x = 0.1), which is a perovskite-related oxide, using perovskite BaTiO{sub 3}–SrTiO{sub 3} (BSTO; Ba{sub y}Sr{sub 1−y}TiO{sub 3}) buffer layers. The BSTO buffer layers formed on (001) (La{sub 0.18}Sr{sub 0.82})(Al{sub 0.59}Ta{sub 0.41})O{sub 3} substrates by magnetron sputtering were fully relaxed with high crystalline quality due to high oxygen partial pressure deposition and post annealing at 950 °C. The lattice constants of the BSTO buffer layers could be controlled in the range of 0.3926–0.3973 nm by changing the Ba content (y = 0.2–0.7). These BSTO buffer layers allow coherent growth of SLCO thin films, and a clear dependence of the superconducting transition temperature on the lattice strain was observed. The fabrication of these BSTO/superconductor heterostructures may provide novel devices composed of functional perovskite thin films, in addition to a general approach for the precise control of lattice strain in functional perovskite thin films. - Highlights: • Ba{sub y}Sr{sub 1−y}TiO{sub 3} buffer layers were developed for the strain tuning of perovskite-related oxides. • Strain effect in Sr{sub 1−x}La{sub x}CuO{sub 2} was investigated by using Ba{sub y}Sr{sub 1−y}TiO{sub 3} buffer layers. • Ba{sub y}Sr{sub 1−y}TiO{sub 3} buffer layers can be used to tune the strain in other perovskite oxides.

  14. Singularity in the positive Hall coeffcient near pre-onset temperatures in high-Tc superconductors

    Science.gov (United States)

    Vezzoli, G. C.; Chen, M. F.; Craver, F.; Moon, B. M.; Safari, A.; Burke, T.; Stanley, W.

    1990-10-01

    Hall measurements using continuous extremely slow cooling and reheating rates as well as employing eqiulibrium point-by-point conventional techniques reveals a clear anomally in RH at pre-onset temperatures near Tc in polycrystalline samples Y1Ba2Cu3O7 and Bi2Sr2Ca2Cu3O10. The anomaly has the appearance of a singularity of Dirac-delta function which parallels earlier work on La1-xSrxCuO4. Recent single crystal work on the Bi-containing high-Tc superconductor is in accord with a clearcut anomaly. The singularity is tentatively interpreted to be associated (upon cooling) with initially the removal of positive holes from the hopping conduction system of the normal state such as from the increased concentration of bound virtual excitons due to increased exciton and hole lifetimes at low temperature. Subsequently the formation of Cooper pairs by mediation from these centers (bound-holes) and/or bound excitons) may cause an ionization of these bound virtual excitons thereby re-introducing holes and electrons into the conduction system at Tc.

  15. Doping effects in high-Tc superconductors

    International Nuclear Information System (INIS)

    Hessel Andersen, N.

    1996-11-01

    The purpose of the project has been to study how the superconducting and magnetic properties of the high temperature superconductors change as function of oxygen stoichiometry and cation doping. The primary system of investigation has been YBa 2 Cu 3 O 6+x , which has been studied as function of oxygen stoichiometry, 0 2 planes, that is necessary for superconductivity, is strongly depending on structural ordering. The static properties and the kinetics of the structural ordering process have been studied experimentally by neutron and high energy synchrotron x-ray diffraction, by Raman scattering, and by computer simulation technique. Not only the oxygen stoichiometry but also the cation doping has been shown to influence the magnetic phases, in some cases in an unexpected manner. Thus, by neutron diffraction experiments it has been shown that doping with non-magnetic Al gives rise to a new magnetic phase. A theoretical model, has been developed. The magnetic phases of the Cu and Nd ordering in NdBa 2 Cu 3 O 6+x , and of the Cu and Pr ordering in PrBa 2 Cu 3 O 6+x have been studied by neutron diffraction with the main purpose of understanding why PrBa 2 Cu 3 O 6+x is magnetic and non-superconducting for all oxygen stoichiometries. In NdBa:2Cu 3 O 6+x studies of the magnetic flux lattice have been carried out by Small Angle Neutron Scattering. Additional structural studies of the superconducting and magnetic phases of related materials, of RENi 2 B 2 C (RE = rare earth), and of oxidized and cation doped materials based on La 2 CuO 4+δ have been carried out. Methods for structural studies and analyses, and equipment for electrical and magnetic characterization have been developed. (EG) 5 tabs., 46 ills., 35 refs

  16. Submillimeter and microwave residual losses in epitaxial films of Y-Ba-Cu-O and Tl-Ca-Ba-Cu-O

    International Nuclear Information System (INIS)

    Miller, D.; Richards, P.L.; Eom, C.B.; Geballe, T.H.; Etemad, S.; Inam, A.; Venkatesan, T.; Martens, J.S.; Lee, W.Y.

    1992-12-01

    We have used a novel bolometric technique and a resonant technique to obtain accurate submillimeter and microwave residual loss data for epitaxial thin films of YBa 2 Cu 3 O 7 , Tl 2 Ca 2 Ba 2 Cu 3 O 10 and Tl 2 CaBa 2 Cu 2 O 8 . For all films we obtain good agreement between the submillimeter and microwave data, with the residual losses in both the Y-Ba-Cu-O and Tl-Ca-Ba-Cu-O films scaling approximately as frequency squared below ∼ 1 THz. We are able to fit the losses in the Y-Ba-Cu-O films to a two fluid and a weakly coupled grain model for the a-b planeconductivity, in good agreement with results from a Kramers-Kronig analysis of the loss data

  17. High magnetic field study of HoBaCo2O5.5 and GdBaCo2O5.5 layered cobaltites: the effect of rare-earth size

    International Nuclear Information System (INIS)

    Frontera, C.; Respaud, M.; Garcia-Munoz, J.L.; Llobet, A.; Carrillo, A.E.; Caneiro, A.; Broto, J.M.

    2004-01-01

    By means of high-pulsed magnetic field up to μ 0 H=32 T we have studied HoBaCo 2 O 5+δ (δ=0.52(1)). The high-field M(H) integrated curves evidence a magnetic field-induced phase transition visible from about T=75 to 275 K. The obtained results are compared with the field-induced transition found for GdBaCo 2 O 5+δ (with δ=0.54(2)). The jump of the magnetization at the field-induced transition is independent of the rare earth at this level of oxygen content. In contrast, we have observed larger values of the critical field, and that the transition persists up to higher temperature, when reducing the rare-earth size. This indicates that the low-temperature antiferromagnetic phase becomes more stable when the size of the rare earth is reduced

  18. The nature of twin boundaries in the high-temperature superconductor YBa2Cu3O7-δ

    International Nuclear Information System (INIS)

    Zhu, Y.; Welch, D.O.

    1999-01-01

    Twin boundaries are the most commonly observed lattice defect in the high-temperature superconductor YBa 2 Cu 3 O 7-δ . Furthermore, the region around a twin boundary for which the structure and composition are seriously affected is of a scale comparable to the coherence length for the superconducting order parameter. Thus, twin boundaries can be important in the behavior of magnetic vortices and the critical current density in this material. In this paper the authors review the results of a wide range of investigations of twin boundary structure and composition by advanced transmission electron microscopy methods, both imaging and analytical in nature. A simple Landau model of twin boundary energy and width is proposed

  19. Scanning tunneling microscopy/spectroscopy on multi-layered cuprate superconductor Ba2Ca5Cu6O12 (O1-x Fx)2

    International Nuclear Information System (INIS)

    Sugimoto, A.; Shohara, K.; Ekino, T.; Watanabe, Y.; Harada, Y.; Mikusu, S.; Tokiwa, K.; Watanabe, T.

    2009-01-01

    Scanning tunneling microscopy/spectroscopy (STM/STS) measurements on multi-layered cuprate superconductor Ba 2 Ca 5 Cu 6 O 12 (O 1-x F x ) 2 are carried out. STM topographies show randomly distributed bright spot structures with a typical spot size of ∼0.8 nm. These bright spots are occupied about 28% per one unit cell of c-plane, which is comparable to the regular amount of apical oxygen of 20% obtained from element analysis. Tunneling spectra simultaneously show both the small and the large gap structures. These gap sizes at 4.9 K are about Δ ∼15 meV and ∼90 meV, respectively. The small gap structure disappears at the temperature close to T C , while the large gap persists up to ∼200 K. Therefore, these features correspond to the superconducting gap and pseudogap, respectively. These facts give evidence for some ordered state with large energy scale even in the superconducting state. For the superconducting gap, the ratio of 2Δ/K B T C = 4.9 is obtained with T C = 70 K, which is determined from temperature dependence of the tunneling spectra.

  20. Pinning characteristics in chemically modified (Nd, Eu, Gd)-Ba-Cu-O superconductors

    Czech Academy of Sciences Publication Activity Database

    Muralidhar, M.; Sakai, N.; Nishiyama, M.; Jirsa, Miloš; Machi, T.; Murakami, M.

    2003-01-01

    Roč. 82, č. 6 (2003), s. 943-945 ISSN 0003-6951 R&D Projects: GA AV ČR IAA1010919 Institutional research plan: CEZ:AV0Z1010914 Keywords : melt-textured superconductors * pinning defects * irreversibility field * bulk superconductors * ternary systems * twin structure Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 4.049, year: 2003

  1. Temperature dependence of the magnetic anisotropy of metallic Y-Ba-Cu-O single crystals in the normal phase

    International Nuclear Information System (INIS)

    Miljak, M.; Zlatic, V.; Kos, I.; Aviani, I.; Hamzic, A.; Collin, G.

    1990-01-01

    The magnetic anisotropy measurements of metallic Y-Ba-Cu-O compounds in the normal phase reveal a temperature-dependent diamagnetic component of the susceptibility that increases with decreasing temperature. The temperature variation of the susceptibility anisotropy and its total change do not seem to be much affected by the presence of the superconductivity at some lower temperature and could not be accounted for by superconducting fluctuations. Rather, the data remind one of the behavior of some quasi-two-dimensional metals with anisotropic Fermi surfaces, reflecting the properties of the low-energy excitations in the normal phase. The anisotropy measurements above the bulk superconducting transition temperature T c reveal the nonlinear effects, which are due to the onset of superconductivity in disconnected grains. The existence of a two-step transition, typical for granular superconductors, should be taken into consideration if the normal-phase susceptibility data are compared with the theoretical predictions in the vicinity of T c

  2. Irradiation effects of high temperature superconductor of lanthanoid oxides

    Energy Technology Data Exchange (ETDEWEB)

    Ueda, Koh-ichi; Kohara, Takao [Himeji Inst. of Tech., Hyogo (Japan)

    1996-04-01

    Neutron irradiation effects on excess oxygen were studied by neutron irradiation on La{sub 2}CuO{sub 4} treated with high pressure oxygen. La{sub 2}CuO{sub 4} was prepared by the usual method and annealed for 10 h under the oxygen pressure of 800-2000 atm. at 600degC. The superconducting transition temperature (Tc) is 27-32K before irradiation (La{sub 2}CuO{sub 4+d}, amount of excess oxygen d=0.03-0.12). Neutron irradiation was carried out by two kinds of experiments. Low irradiation dose test at low temperature (LTL: {approx}20-200K, storage in LN{sub 2}) showed Tc decreased more slowly than that of high temperature range. Experiment at high temperature (Hyd:{approx}80deg{yields}, storage at room temperature) showed -10K/10{sup 18}n/cm{sup 2}, the decrease of Tc was three times larger than that of YBCO type superconductor. (S.Y.)

  3. Tc dependence on the number of CuO2 planes in multilayered Ba2Can-1CunO2n(O, F)2 superconductors

    International Nuclear Information System (INIS)

    Iyo, A; Tanaka, Y; Kodama, Y; Kito, H; Tokiwa, K; Watanabe, T

    2006-01-01

    Multilayered cuprates of Ba 2 Ca n-1 Cu n O 2n (O, F) 2 (F-02(n-1)n) with n = 5 - 9 have been synthesized by using high pressure synthesis method in order to investigate the variation of T c . The temperature dependence of susceptibility showed that the T c (about 80 K) does not depend on n for n 5 - 9. This result can be explained using the carrier imbalance model in multilayered cuprates. Charge reservoir layers supply most of the carriers to adjacent CuO 2 planes (OP) and the OP keeps the T c constant even for large n

  4. Signature of electron-phonon interaction in high temperature superconductors

    Directory of Open Access Journals (Sweden)

    Vinod Ashokan

    2011-09-01

    Full Text Available The theory of thermal conductivity of high temperature superconductors (HTS based on electron and phonon line width (life times formulation is developed with Quantum dynamical approach of Green's function. The frequency line width is observed as an extremely sensitive quantity in the transport phenomena of HTS as a collection of large number of scattering processes. The role of resonance scattering and electron-phonon interaction processes is found to be most prominent near critical temperature. The theory successfully explains the spectacular behaviour of high Tc superconductors in the vicinity of transition temperature. A successful agreement between theory and experiment has been obtained by analyzing the thermal conductivity data for the sample La1.8Sr0.2CuO4 in the temperature range 0 − 200K. The theory is equally and successfully applicable to all other high Tc superconductors.

  5. Investigation of Pb doping on electrical, structural and superconducting properties of YBa2-xPbxCu3O7-δ superconductors

    Science.gov (United States)

    Ezzatpour, S.; Sharifzadegan, L.; Sarvari, F.; Sedghi, H.

    2018-06-01

    In this study the high temperature superconductor YBa2-xPbxCu3O7-δ with doping x = ,0.05,0.1,0.15 were prepared by the standard solid-state reaction method. The effect of Pb substitution on Ba site of YBCO superconducting system, structural, electrical and superconducting properties of Y-based superconductor has been investigated. The measurements of dc resisitivity were performed on all samples with four-probe method using low frequency/lowAC current (4 mA) . The superconducting temperature, Tc, were determined from the resistivity versus temperature (R-T) curves. Results show that Pb doping reduced the cirtical temperature(Tc) and superconductivity properties of our samples. The maximum and the minimum Tc were observed for the samples with x = 0.15 and x = 0.1 respectively. The structure and phase purity of samples were examined by the X-ray powder diffraction technique (XRD) performed by means of D8 Advance Bruker diffractometer with Cu kα radiation. The grain morphology of surface of the samples was analyzed by sacanning electron microscopy (SEM). XRD patterns of polycrystalline materials of composition YBa2-xPbxCu3O7-δ revealed that all prepared samples are orthorhombic. All of the peaks of YBCO and YBa2-xPbxCu3O7-δ have been used for the estimation of volume fractions of the phases and ignored the void peaks.

  6. Irreversibility Curve on Y1–xLuxBa2Cu3O7–δ (x=0.4, 0.5 and 0.6) superconducting

    International Nuclear Information System (INIS)

    Grimaldos, J F Cepeda; Supelano G, I; Santos, A Sarmiento; Chiquillo, M V; Martínez B, D; Vargas, C A Parra

    2014-01-01

    The irreversibility line in the H–T plane divides the irreversible and reversible behaviour of the magnetization which is of importance for the characterization of high T c superconductors. In this work, we report the production of Y 1–X Lu X Ba 2 Cu 3 O 7–δ (X=0.4, 0.5 and 0.6) superconducting system using the usual solid state reaction method. The irreversibility line H–T plane for the Y 1–X Lu X Ba 2 Cu 3 O 7–δ polycrystalline sample was investigated. The curves of magnetization ZFC (cero field cooled)- FC (field cooled) were measured in magnetic fields between 100 Oe and 4000 Oe, and allowed to obtain the values for irreversibility and critical temperatures

  7. Effect of iron doping on Y-Ba-Cu-O

    International Nuclear Information System (INIS)

    Abd Halim Shaari; Mansor Hashim; Sidek Hj Abd Aziz; Laily Rafiah Abdullah

    1991-01-01

    Study on the effect of iron doping at different values of doping percentage (0.00< x<0.06) and hence the influence of magnetic iron on Y-Ba-Cu-O superconductor has been carried out. The conventional technique of sintering is used in preparing the ceramic materials. The crystal structure and their lattice parameters are determined from X-ray diffraction measurements. Observation on the dependence of resistance on temperature is made between room temperature to the boiling point of liquid nitrogen, using four-probe techniques. Magnetisation properties namely the Meissner Effect is also observed by levitating a small piece of permanent magnet on the cooled sample. The X-ray diffraction data show that the phase transitions have been observed; from orthorhombic to tetragonal when the iron doping exceeded ∼0.02. Transition temperature, Tc decrease from ∼87.7K to ∼83K. Meissner Effect is observed for sample doped up to 2% only

  8. Exponential temperature dependence of the critical transport current in Y-Ba-Cu-O thin films

    International Nuclear Information System (INIS)

    Yom, S.S.; Hahn, T.S.; Kim, Y.H.; Chu, H.; Choi, S.S.

    1989-01-01

    We have measured the critical currents in rf-sputtered YBa 2 Cu 3 O/sub 7-x/ thin films deposited on polycrystalline yttria-stabilized zirconia substrates as a function of temperature down to 10 K. The dependence of the granular films at low temperature indicated exponential behavior which is similar to the superconductor-normal metal-superconductor (S-N-S) type tunneling junctions. For the films with a grain size of approximately 1 μm, we observed two exponential decay constants, which suggest that Josephson junctions limiting the transport critical current are possible both at the grain boundaries and at twin boundaries

  9. Barium contributions to the valence electronic structure of YBa2Cu3O7-δ, PrBa2Cu3O7-δ, and other barium-containing compounds

    International Nuclear Information System (INIS)

    Mueller, D.R.; Wallace, J.S.; Jia, J.J.; O'Brien, W.L.; Dong, Q.; Callcott, T.A.; Miyano, K.E.; Ederer, D.L.

    1995-01-01

    Monochromatic photon beams were used to excite barium N IV,V soft x-ray emission spectra from YBa 2 Cu 3 O 7-δ , PrBa 2 Cu 3 O 7-δ , BaF 2 , and BaTiO 3 . Near threshold excitation was used to demonstrate that small contributions to the barium N V and N IV emission spectra in the energy region above the 5p→4d core-core transitions do not arise as satellite emission from transitions in multiply excited atoms but rather occur as a result of transitions from the valence states. The emission spectrum of YBa 2 Cu 3 O 7-δ and PrBa 2 Cu 3 O 7-δ reveals a contribution to the electronic density of states at the barium site in the region near the Fermi level. The YBa 2 Cu 3 O 7-δ compound is a superconductor and PrBa 2 Cu 3 O 7-δ is an insulator. It has been proposed that the difference between them is due to mixing of praseodymium and barium among the sites occupied by yttrium and barium, with an accompanying change in electronic structure. However, our measurements indicate that the barium partial density of states for the two compounds are essentially identical

  10. X-ray photoemission studies of Zn doped Cu1-xTl xBa2Ca2Cu 3-yZn yO10-δ (y = 0, 2.65) superconductors

    International Nuclear Information System (INIS)

    Khan, Nawazish A.; Mumtaz, M.; Ahadian, M.M.; Iraji-zad, Azam

    2007-01-01

    The X-ray photoemission (XPS) measurements of Cu 1-x Tl x Ba 2 Ca 2 Cu 3-y Zn y O 10-δ (y = 0, 2.65) superconductors have been performed and compared. These studies revealed that the charge state of thallium in the Cu 0.5 Tl 0.5 Ba 2 O 4-δ charge reservoir layer in Zn doped samples is Tl 1+ , while it is a mix of Tl 1+ and Tl 2+ in Zn free samples. The binding energy of Ba atoms in the Zn doped samples is shifted to higher energy, which when considered along with the presence of Tl 1+ suggested that it more efficiently directed the carriers to ZnO 2 and CuO 2 planes. The evidence of improved inter-plane coupling witnessed in X-ray diffraction is also confirmed by XPS measurements of Ca atoms in the Zn doped samples. The shift of the valance band spectrum in these Zn doped samples to higher energies suggested that the electrons at the top edge of the valance band were tied to a higher binding energy (relative to samples without Zn doping), which most likely resulted in a much lower energy state of the system in the superconducting state. The stronger superconducting state arising out of these effects is witnessed in the form of increased T c (R 0), J c and the extent of diamagnetism in the final compound

  11. (Cu,C)Ba2Ca3Cu4Ox-(LiF)y: addition of LiF-an effective way to synthesize overdoped superconductor

    International Nuclear Information System (INIS)

    Badica, P; Iyo, A; Aldica, G; Kito, H; Crisan, A; Tanaka, Y

    2004-01-01

    (Cu,C)Ba 2 Ca 3 Cu 4 O x superconductor with addition of y mol LiF has been synthesized by a high-pressure method. For the same synthesis conditions it was found that (almost) single-phase Cu, C-1234 samples can be synthesized for y LiF = 0-0.1 if the amount of z mol AgO oxidizer is increased linearly from z AgO = 0.45 to 0.73 and for y LiF 0.1-0.2 if z AgO = 0.73 constant. Transport measurements (ρ(T) and room-temperature Seebeck coefficient) have shown that these samples are overdoped: LiF is an effective addition for synthesis of overdoped Cu, C-1234 with a controlled level of carriers. LiF addition continuously decreases T c . The critical point at y LiF = 0.1 is discussed as the solubility limit of LiF and/or the point where the doping mechanism changes. It is proposed that the reason is the reaction of extra Li with C and O to form Li 2 CO 3 , inducing a lower concentration of C in Cu, C-1234/LiF crystals, and at the same time a possible substitution of Li not only for the Cu site but also for the Ca site, resulting in formation of a higher amount of residual Ca 0.828 CuO 2 (for y LiF >0.1). LiF induces the formation of a liquid phase and acts as a flux promoting the formation of Cu,C-12 (n-1)n with n ≥ 4. LiF modifies to some degree the grain growth from a 3D to a 2D type (thinner platelike grains have been observed in the LiF added samples)

  12. Chemically etched edges of YBa2Cu3O7 films for interconnects, crossovers and Josephson junctions

    International Nuclear Information System (INIS)

    Poppe, U.; Faley, M.I.; Urban, K.; Soltner, H.

    1993-01-01

    To produce damage-free edges is one of the main problems during the preparation of Josephson edge-type junctions and interconnects in multilayer structures including high temperature superconductors. The inherently short and anisotropic coherence length in high temperature superconductors makes it also difficult to fabricate Josephson junctions from these materials. One promising technique which helps to overcome such problems using a nonaqueous chemical etching with a Br-ethanol solution was first presented in a recent publication. Here we report results obtained with the use of this method: test of insulation properties of PrBa 2 Cu 3 O 7 , PrBa 2 Cu 2.85 Ga 0.15 O 7 , and SrTiO 3 used for crossovers and Josephson junctions. Some features of interconnects and Josephson junctions, prepared on the basis of the chemical technique are also discussed. (orig.)

  13. Spins in the vortices of a high-temperature superconductor

    DEFF Research Database (Denmark)

    Lake, B.; Aeppli, G.; Clausen, K.N.

    2001-01-01

    Neutron scattering is used to characterize the magnetism of the vortices for the optimally doped high-temperature superconductor La2-xSrxCuO4 (x = 0.163) in an applied magnetic field. As temperature is reduced, Low-frequency spin fluctuations first disappear with the loss of vortex mobility......, but then reappear. We find that the vortex state can be regarded as an inhomogeneous mixture of a superconducting spin fluid and a material containing a nearly ordered antiferromagnet. These experiments show that as for many other properties of cuprate superconductors, the important underlying microscopic forces...

  14. Tuning the electrical and optical properties of Gd{sub 1-x}Ca{sub x}BaCo{sub 2}O{sub 5+δ} (x = 0–0.5) using solar energy

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Yi; Zhang, Rong; Wei, Ling [State Key Laboratory of Materials-Orient Chemical Engineering, College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009 (China); Lu, Chunhua, E-mail: chhlu@njtech.edu.cn [State Key Laboratory of Materials-Orient Chemical Engineering, College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009 (China); Fang, Zhenggang; Ni, Yaru [State Key Laboratory of Materials-Orient Chemical Engineering, College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009 (China); Xu, Zhongzi, E-mail: zzxu@njtech.edu.cn [State Key Laboratory of Materials-Orient Chemical Engineering, College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009 (China); Tao, Shunyan [Key Laboratory of Inorganic Coating Materials, Chinese Academy of Sciences, Shanghai 200050 (China)

    2016-06-15

    This study reveals that the use of a Ca dopant can increase the solar absorption of GdBaCo{sub 2}O{sub 5+δ}, with an optimal composition of Gd{sub 0.8}Ca{sub 0.2}BaCo{sub 2}O{sub 5} achieving 85% solar absorptance. Electrical conductivity measurements revealed that this composition allows for faster insulator-metal transition and higher conductivity, with the observed variation in conductivity with 0.8 W/cm{sup 2} of solar illumination explained in terms of a first-order spin-state transition. Thermal radiation imaging confirmed that regions of different radiative temperature are related to a change in free carriers that promote scattering, and therefore, cause an increase in infrared reflection. This rapid electrical conductivity transition and the low infrared radiation properties at high temperatures strongly suggest that Gd{sub 0.8}Ca{sub 0.2}BaCo{sub 2}O{sub 5} could be used in a variety of potential fields, such as high-temperature thermosensitive or thermal storage materials. - Highlights: • The solar absorption properties of GdBaCo{sub 2}O{sub 5+δ} can be improved by Ca doping. • Gd{sub 0.8}Ca{sub 0.2}BaCo{sub 2}O{sub 5} shows ultrafast conductivity transition induced by solar energy. • Gd{sub 0.8}Ca{sub 0.2}BaCo{sub 2}O{sub 5} exhibits low thermal radiative properties at high temperature.

  15. Hybrid crystals of cuprates and iron-based superconductors

    Science.gov (United States)

    Xia, Dai; Cong-Cong, Le; Xian-Xin, Wu; Jiang-Ping, Hu

    2016-07-01

    We propose two possible new compounds, Ba2CuO2Fe2As2 and K2CuO2Fe2Se2, which hybridize the building blocks of two high temperature superconductors, cuprates and iron-based superconductors. These compounds consist of square CuO2 layers and antifluorite-type Fe2 X 2 (X = As, Se) layers separated by Ba/K. The calculations of binding energies and phonon spectra indicate that they are dynamically stable, which ensures that they may be experimentally synthesized. The Fermi surfaces and electronic structures of the two compounds inherit the characteristics of both cuprates and iron-based superconductors. These compounds can be superconductors with intriguing physical properties to help to determine the pairing mechanisms of high T c superconductivity. Project supported by the National Basic Research Program of China (Grant No. 2015CB921300), the National Natural Science Foundation of China (Grant Nos. 1190020 and 11334012), and the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB07000000).

  16. (Cu,C)Ba2Ca3Cu4Ox (LiF)y: addition of LiF—an effective way to synthesize overdoped superconductor

    Science.gov (United States)

    Badica, P.; Iyo, A.; Aldica, G.; Kito, H.; Crisan, A.; Tanaka, Y.

    2004-03-01

    (Cu,C)Ba2Ca3Cu4Ox superconductor with addition of y mol LiF has been synthesized by a high-pressure method. For the same synthesis conditions it was found that (almost) single-phase Cu, C-1234 samples can be synthesized for yLiF = 0-0.1 if the amount of z mol AgO oxidizer is increased linearly from zAgO = 0.45 to 0.73 and for yLiF = 0.1-0.2 if zAgO = 0.73 = constant. Transport measurements (rgr(T) and room-temperature Seebeck coefficient) have shown that these samples are overdoped: LiF is an effective addition for synthesis of overdoped Cu, C-1234 with a controlled level of carriers. LiF addition continuously decreases Tc. The critical point at yLiF = 0.1 is discussed as the solubility limit of LiF and/or the point where the doping mechanism changes. It is proposed that the reason is the reaction of extra Li with C and O to form Li2CO3, inducing a lower concentration of C in Cu, C-1234/LiF crystals, and at the same time a possible substitution of Li not only for the Cu site but also for the Ca site, resulting in formation of a higher amount of residual Ca0.828CuO2 (for yLiF>0.1). LiF induces the formation of a liquid phase and acts as a flux promoting the formation of Cu,C-12 (n-1)n with n \\ge 4 . LiF modifies to some degree the grain growth from a 3D to a 2D type (thinner platelike grains have been observed in the LiF added samples).

  17. Investigation of the properties of carbon-base nanostructures doped YBa{sub 2}Cu{sub 3}O{sub 7−δ} high temperature superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Dadras, Sedigheh, E-mail: dadras@alzahra.ac.ir; Ghavamipour, Mahshid

    2016-03-01

    In this research, we have investigated the effects of three samples of carbon-base nanostructures (carbon nanoparticles, carbon nanotubes and silicon carbide nanoparticles) doping on the properties of Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7−δ} (YBCO) high temperature superconductor. The pure and doped YBCO samples were synthesized by sol–gel method and characterized by resistivity versus temperature (ρ–T), current versus voltage (I–V), through X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis. The results confirmed that for all the samples, the orthorhombic phase of YBCO compound is formed. We found that the pinning energy and critical current density of samples increase by adding carbon nanostructures to YBCO compound. Also critical temperature is improved by adding carbon nanotubes to YBCO compound, while it does not change much for carbon and silicon carbide nanoparticles doped compounds. Furthermore, the samples were characterized by UV–vis spectroscopy in 300 K and the band gap of the samples was determined. We found that the carbon nanotubes doping decreases YBCO band gap in normal state from 1.90 eV to 1.68 eV, while carbon and SiC nanoparticles doping increases it to 2.20 and 3.37 eV respectively.

  18. Influence of antimony oxide on the properties of YBa[sub 2]Cu[sub 3]O[sub 7-x] superconductors prepared by melt quenching

    Energy Technology Data Exchange (ETDEWEB)

    Tenzler, T.; Altakh, O.; Zaitzev, O. (Mendeleev Univ. of Chemical Technology, Moscow (Russia))

    1992-12-01

    The potential usefulness of glass-technological procedures to prepare oxidic high-temperature superconductors is well-known. Samples in the system Y-Ba-Cu-O have been produced by a melt process and subsequent annealing steps. Antimony oxides have been added to the base system and their influence on the properties of the products has been studied. The samples have been analyzed by X-ray diffraction and differential thermogravimetry as well as by electrical resistance measurements. With the addition of antimony oxides the type and quantities of the crystalline phases changed both in the quenched samples and in the samples annealed at temperatures above 900deg C and also the density increased. It was found that the samples containing antimony oxides as well as the samples of the base system become superconductors at a temperature higher than the liquid nitrogen temperature. Only the annealing time is much less than that for the pure superconductor. (orig.).

  19. Characteristics of YBa2Cu3O7 high-Tc superconductor with KCl

    Science.gov (United States)

    Yoon, Ki Hyun; Chang, Sung Sik

    1990-03-01

    The lattice parameters, microstructural change, transition temperature, and electrical properties of the YBa2-xKxCu3O7 high-Tc superconductor in the range from x=0 to x=0.25 have been investigated. The high-Tc orthorhombic phase increases with increasing KCl up to x=0.20, above which it decreases. The lattice parameters decrease with increasing KCl up to x=0.10, and then become nearly uniform. The grain size increases with increasing KCl up to x=0.20 due to its role as sintering agent. The specimens with x=0.2 have transition temperatures of 96 K and high magnetic susceptibility due to the contraction of lattice parameters a and b and the increase of orthorhombic distortion.

  20. High-T/sub c/ superconductor YBa2Cu3O/sub 7-//sub δ/ studied by positron annihilation

    International Nuclear Information System (INIS)

    Wang, S.J.; Naidu, S.V.; Sharma, S.C.; De, D.K.; Jeong, D.Y.; Black, T.D.; Krichene, S.; Reynolds, J.R.; Owens, J.M.

    1988-01-01

    We have measured the positron lifetime and the Doppler broadening spectra in the high-temperature superconductor YBa 2 Cu 3 O/sub 7-//sub δ/ as a function of temperature between 77 and 295 K. Positron-lifetime and Doppler-broadening data show new features in the superconducting phase. These results are interpreted in terms of positron localization in lattice distortions and positron surface states

  1. Partial substitution of Zn Effects on the Structural and Electrical Properties of High Temperature Hg0.95Ag0.05Ba2Ca2Cu3O8+δ Superconductors

    Science.gov (United States)

    Abed, Noor S.; Fathi, Sabah J.; Jassim, Kareem A.; Mahdi, Shatha H.

    2018-05-01

    The effect of the Ag partial substitution at Hg site in HgOδ layer and Zn partial substitution at Ca site in CaO layer on the structure,Tc,electrical properties, and oxygen content for Hg-1223 have been studied. Bulk polycrystalline Hg1-xAgxBa2Ca2-yZnyCu3O8+δ compound samples with x=0.05 and y=0.0, 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3, are synthesized by a solid state reaction process. Structural properties are studied by using X-ray powder pattern, the high temperature phase superconductor (Hg-1223) of the tetragonal structure didn't change with the partial substitution of Zn and Ag ions, lattice parameters c,c/a are established to vary with Ag and Zn- substitution. The surface morphology has been studied by using atomic force microscopes (AFM), showed that all specimens have good crystalline and homogeneous surface. Also give a best nano size value is 75.72 nm at x=0.05 and y=0.3. Four probe technique is used to measure Tc. The Tc were found to be increases from 129 K to 147 K and oxygen content were found to be increases with increasing Zn. In addition, dielectric properties (dielectric constant, dielectric loss factor, and the alternating electrical conductivity) are characterized directly by relating with Ag and Zn concentration.

  2. Flux pinning property in a single crystal NdBa2Cu3Oy superconductor

    International Nuclear Information System (INIS)

    Hasan, M.N.; Kurokawa, T.; Kiuchi, M.; Otabe, E.S.; Matsushita, T.; Chikumoto, N.; Machi, T.; Muralidhar, M.; Murakami, M.

    2005-01-01

    The critical current density J c and the apparent pinning potential U 0 * in a single crystal NdBa 2 Cu 3 O y superconductor which shows a broad peak effect are investigated by measuring a DC magnetization and its relaxation. The field-induced pinning mechanism does not explain the temperature dependence of peak field B p and dip field B d . The experimental results of J c and U 0 * are compared with the theoretical analysis based on the flux creep-flow model, taking the distribution of the flux pinning strength into account. The number of flux lines in the flux bundle (g 2 ), the most probable value of pinning strength (A m ) and distribution width (σ 2 ) are determined so that a good fit is obtained between the experimental and theoretical results. The behavior of these parameters is discussed in correspondence to the disorder transition of flux lines

  3. Composition changes in sputter deposition of Y-Ba-Cu-O films

    International Nuclear Information System (INIS)

    Hoshi, Y.; Naoe, M.

    1989-01-01

    The authors discuss the mechanism of the composition change in sputter deposition of Y-BA-Cu-O film from YBa 2 Cu 3 O 7-chi target investigated by means of a rf planar magnetron sputtering apparatus. Film composition changes significantly with not only substrate temperature Ts and sputtering gas pressure, but also substrate position. Lack of Cu and Ba content is significant in the film deposited at the substrate position just above the erosion area of the sputtering target. Suppression of bombardment of the substrate surface by negative ions emitted from the target and substrate is effective in increasing Cu and Ba content in the film. These results indicate not only that the sticking probability of the sputtered particles changes with Ts and incident particle energy, but also that high energy particle bombardment of the substrate surface plays an important role in the change of the film composition

  4. Effect of rare-earth ion size on local electron structure in RBa2Cu3O7-δ (R = Tm, Dy, Gd, Eu, Nd and Y) superconductors: A positron study

    International Nuclear Information System (INIS)

    Chen Zhenping; Zhang Jincang; Su Yuling; Xue Yuncai; Cao Shixun

    2006-01-01

    The effects of rare-earth ionic size on the local electron structure, lattice parameters and superconductivity have been investigated by positron annihilation technique (PAT) and related experiments for RBa 2 Cu 3 O 7-δ (R = Tm, Dy, Gd, Eu, Nd and Y) superconductors. The local electron density n e is evaluated as a function of the rare-earth radius. The results show that both the bulk-lifetime τ B and the defect lifetime τ 2 increase with increasing rare-earth ionic radius, while the local electron density n e decrease with increasing rare-earth ionic radius. These results prove that the changes of n e , the degree of orthorhombic distortion and the coupling between the Cu-O chains and the CuO 2 planes all have an effect on the superconductivity of RBa 2 Cu 3 O 7-δ systems

  5. Synthesis and luminescence properties of BaTiO3:RE (RE = Gd , Dy ...

    Indian Academy of Sciences (India)

    thermoluminescence (TL) properties of BaTiO3 samples doped with Gd3+, Dy3+, Tb3+ and Lu3+ were investigated. ... electron microscope using an accelerating voltage of 20 kV. .... doping of 1% mole Gd3+ ion into the BaTiO3 compound.

  6. A preliminary X-ray diffraction study of the tetragonal superconducting oxide LaBa2Cu3O7-δ

    International Nuclear Information System (INIS)

    Hervieu, M.; Nguyen, N.; Michel, C.

    1987-01-01

    X-ray diffraction study of LaBa 2 Cu 3 O 7-δ showed that this tetragonal oxide exhibits an ordered oxygen deficient perovskite structure. It appears that the oxygen vacancy distribution differs from that observed for the orthorhombic superconductor YBa 2 Cu 3 O 7-δ . A structural model is proposed and discussed [fr

  7. Giant T{sub c} shift in HgBa{sub 2}CaCu{sub 2}O{sub 6+{delta}} and TlBa{sub 2}CaCu{sub 2}O{sub 7{minus}{delta}} superconductors due to Hg-Tl exchange

    Energy Technology Data Exchange (ETDEWEB)

    Gapud, A.A.; Wu, J.Z.; Kang, B.W.; Yan, S.L.; Xie, Y.Y. [Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045-2151 (United States); Siegal, M.P. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

    1999-01-01

    The irreversibility lines of epitaxial thin films of HgBa{sub 2}CaCu{sub 2}O{sub 6+{delta}} and TlBa{sub 2}CaCu{sub 2}O{sub 7{minus}{delta}}, whether deduced from field-induced magnetoresistive broadening or onset of nonhysteretic magnetization, were found to coincide when plotted against reduced temperature, showing the same exponential-decay temperature behavior for T/T{sub c}{lt}0.8 and power-law behavior for T/T{sub c}{gt}0.8 (where T{sub c} is zero-field, zero-resistivity critical temperature). These results indicate that replacing Tl with Hg has no noticeable effect on the anisotropy and suggests that T{sub c} is not determined by anisotropy. {copyright} {ital 1999} {ital The American Physical Society}

  8. Josephson plasma resonance in vortex filament state of high temperature superconductors

    International Nuclear Information System (INIS)

    Matsuda, Yuji; Gaifullin, M.B.

    1996-01-01

    High temperature superconductors have the crystalline structure in which two-dimensional CuO 2 planes are piled in layers, consequently, the anisotropy of electroconductivity arises, and this brings about stable and low energy Josephson plasma in superconducting state. Also as to the vortex filament state of high temperature superconductors, the effect of thermal fluctuation due to low dimensionality, short coherence length and high transition temperature becomes conspicuous. In reality, these plasma and vortex filament state are related closely. Light reflection and plasma edge in superconducting state, Josephson plasma resonance in the vortex filament state of BiO 2 Sr 2 CaCu 2 O 8+δ , the plasma vibration in Josephson junction, Josephson plasma in magnetic field, Josephson plasma in the liquid state of vortex filament, Josephson plasma in the solid state of vortex filament, and Josephson plasma in parallel magnetic field are reported. The Josephson plasma resonance is the experimental means for exploring vortex filament state from microscopic standpoint, and its development hereafter is expected. (K.I.)

  9. Microwave properties of YBa2Cu3O7-δ/PrBa2Cu3O7-δ superlattices

    International Nuclear Information System (INIS)

    Carlos, W.E.; Kaplan, R.; Lowndes, D.H.; Norton, D.P.

    1992-01-01

    We have used non-resonant microwave absorption to study c-axis YBa 2 Cu 3 O 7-δ /PrBa 2 Cu 3 O 7-δ superlattices and compare the response to a film of similarly grown YBa 2 Cu 3 O 7-δ (YBCO). Near the respective transition temperatures, the response of the superlattice samples and the YBCO film have similar amplitudes and orientation dependences. This is consistent with the microwave loss being related to magnetic flux penetration at (110) slip planes. At lower temperatures, the response of the superlattices is much stronger than that of the YBCO film and, while both responses are hysteretic at low temperatures, the widths of the hysteresis have opposite orientation dependences, which we attribute to the role of the PrBa 2 Cu 3 O 7-δ layers. (orig.)

  10. Ca doping of TSMTG-YBa2Cu3O7-δ/Y2BaCuO5 composites

    International Nuclear Information System (INIS)

    Delorme, F.; Harnois, C.; Monot-Laffez, I.; Marinel, S.

    2002-01-01

    Calcium doped YBa 2 Cu 3 O 7-δ /Y 2 BaCuO 5 bulk samples have been synthesised by the top-seeding-melt-texture growth (TSMTG) process up to 1 wt.% of CaCO 3 . Calcium additions up to 0.25 wt.% of CaCO 3 do not change the decomposition temperature whereas additions of 1 wt.% of CaCO 3 lead to an increase of the decomposition temperature of about 10 deg. C. This difference is not important enough to change the thermal cycle used to process YBa 2 Cu 3 O 7-δ undoped bulk samples. Microstructure studies show that no precursor or secondary phases containing calcium are present in the samples. Energy dispersive spectroscopy analyses have shown that Ca is present both in the YBa 2 Cu 3 O 7-δ matrix and the Y 2 BaCuO 5 particles. The position of the calcium atoms in the superconducting matrix is discussed. The calcium doped samples present slightly depressed critical temperatures but drastically depressed critical current densities

  11. Deficient by oxygen perovskites and superconductor with transition temperature 93 K

    International Nuclear Information System (INIS)

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

    1988-01-01

    Structural changes in some perovskites deficient by oxygen is reviewd. The structure of the high-temperature YBa 2 Cu 3 O 7-x superconductor is shown to develop usual for perovskites properties and at the same time to possess specific features. The specific feature includes the fact that ordering of vacancies and oxygen atoms is the consequence of Ba 2+ and Y 3+ ordering in positions A. Such ordering causes the removal of oxygen atoms plane from the structure and accurrence of pyramidal-coordinated atoms Cu2 in positions B. 22 refs.; 3 figs.; 2 tabs

  12. μSR-investigation of high-Tc superconductors at the LNP JINR phasotron

    International Nuclear Information System (INIS)

    Bezhitadze, D.T.; Borovinskaya, I.P.; Burianek, J.

    1989-01-01

    High-T c superconductors La 2-x Sr x CuO 4 (x=0+0.25), Ho(Er)Ba 2 Cu 3 O 7-y and Bi-Sr-Ca-Cu-O (the main phase 2212 with a small admixture of the 2223-phase) were investigated in the zero and 100+400 Oe transverse external magnetic fields in the temperature interval 4.2+300 K. The magnetic ordering for the La 2-x Sr x CuO 4 samples with x=0.00 and x=0.01 occurs below T N ∝250 K and T N ∝170 K respectively. A considerable increase in the distribution width of the magnetic field on the muon with an increase in the Sr-content indicates an enhancement of the Cu 2+ magnetic moment deviation from the magnetic ordering axis. The results of the analysis of the μSR spectra indicate the formation of the spin glass state in the La 1.93 Sr 0.07 CuO 4 sample. In contrast to the behaviour of the HoBa 2 Cu 3 O 7-y ceramic the magnetic ordering of the Er-atoms in the ErBa 2 Cu 3 O 7-y sample is not observed in the conparable temperature interval. Our data has also allowed the magnetic field penetration depth λ perpendicular (0) to be determined: 3200±70 A for La 1.9 Sr 0.1 CuO 4 , 2420±60 A for La 1.85 Sr 0.15 CuO 4 , 2000±50 A for Bi-Sr-Ca-Cu-O (phase 2212), 1600±50 A for ErBa 2 Cu 3 O 7-y . 20 refs.; 8 figs

  13. Anisotropy of the Irreversibility Field for Zr-doped (Y,Gd)Ba2<\\sub>Cu3<\\sub>O<7-x<\\sub> Thin Films up to 45 T

    Energy Technology Data Exchange (ETDEWEB)

    Tarantini, C. [Florida State University; Jaroszynski, J. [Florida State University; Kametani, F. [Florida State University; Zuev, Yuri L [ORNL; Gurevich, A. [Florida State University; Chen, Y [SuperPower Incorporated, Schenectady, New York; Selvamanickam, V. [SuperPower Incorporated, Schenectady, New York; Larbalestier, D. C. [Florida State University; Christen, David K [ORNL

    2011-01-01

    The anisotropic irreversibility fieldBIrr of twoYBa2Cu3O7 x thin films dopedwith additional rare earth (RE)= (Gd, Y) and Zr and containing strong correlated pins (splayed BaZrO3 nanorods and RE2O3 anoprecipitates) has been measured over a very broad range up to 45 T at temperatures 56 K < T < Tc. We found that the experimental angular dependence of BIrr ( ) does not follow the mass anisotropy scaling BIrr ( ) = BIrr (0)(cos2 + 2 sin2 ) 1/2, where = (mc/mab)1/2 = 5 6 for the RE-doped Ba2Cu3O7 x (REBCO) crystals, mab and mc are the effective masses along the ab plane and the c-axis, respectively, and is the angle between B and the c-axis. For B parallel to the ab planes and to the c-axis correlated pinning strongly enhances BIrr , while at intermediate angles, BIrr ( ) follows the scaling behavior BIrr ( ) (cos2 + 2 RP sin2 ) 1/2 with the effective anisotropy factor RP 3 significantly smaller than the ass anisotropy would suggest. In spite of the strong effects of c-axis BaZrO3 nanorods, we found even greater enhancements of BIrr for fields along the ab planes than for fields parallel to the c-axis, as well as different temperature dependences of the correlated pinning contributions to BIrr for B//ab and B//c. Our results show that the dense and strong pins, which can now be incorporated into REBCO thin films in a controlled way, exert major and diverse effects on the measured vortex pinning anisotropy and the irreversibility field over wide ranges of B and T . In particular, we show that the relative contribution of correlated pinning to BIrr for B//c increases as the temperature increases due to the suppression of thermal fluctuations of vortices by splayed distribution of BaZrO3 nanorods.

  14. Investigation on the bisoliton mechanism of high-temperature superconductors

    International Nuclear Information System (INIS)

    Zhang Lingyun; Li Bozang; Pu Fucho; Lin Jiatih

    1996-01-01

    Microscopic parameters in the Davydov model are calculated on the basis of the bisoliton idea. The energy gap is obtained from combining the condition for the solution of Davydov's equation with the condensation energy of the superconductive state in zero field, and some characteristic parameters of high-temperature superconductors such as coherence length, penetration depth, and density of critical current for a thin film in weak magnetic field are given. It is also proved that lattice displacement in Davydov's equation satisfies the φ 4 field form. The critical temperature and the coefficient of linear specific heat of high-temperature superconductors are studied from the statistics of lattice kinks. The agreement between theoretical and experimental values for YBaCuO oxide ceramics suggests that the bisoliton model gives a reasonable explanation of high-temperature superconductivity. (orig.)

  15. X-ray absorption spectroscopy on high-temperature superconductors and related compounds

    International Nuclear Information System (INIS)

    Pellegrin, E.J.H.A.

    1995-07-01

    The electronic structure of the cuprate high-temperature superconductors La 2-x Sr x CuO 4+δ , Tl 2 Ba 2 CaCu 2 O 8 and Tl 2 Ba 2 Ca 2 Cu 3 O 10 has been investigated using polarization-dependent near-edge X-ray absorption fine structure spectroscopy (NEXAFS). In addition, La 2-x Sr x NiO 4+δ has been included in the actual study as an isostructural analogue to the La 2-x Sr x CuO 4+δ system. It appears that the electronic structure of these compounds corresponds to that of a p-type doped charge-transfer insulator including electron-electron interactions on the Cu(Ni) sites and a strong hybridization between Cu(Ni) and O atoms. It is concluded that the low-energy excitations in these compounds can be described on the basis of an effective one-band Mott-Hubbard model. The polarization-dependence of the above spectra gives evidence for the strong in-plane character of the intrinsic and the doped holes. The small amount and the doping-dependence of the out-of-plane character of these charge carriers rule out models for a microscopic mechanism of superconductivity based on a large amount of hole states in the corresponding Apex-O2p z /Cu3d 3z 2 -r 2 orbitals. On the other hand, the reduction of this anisotropy in the overdoped compounds together with similar findings in the macroscopic properties seems to indicate a detrimental influence of non-planar orbitals on the superconducting properties. The differences in the energetic ordering and atomic character of the states close to the Fermi level between the undoped compounds La 2 CuO 4+δ , La 2 NiO 4+δ , and NiO have been determined from the NEXAFS data. It is found that these differences can be explained by the different size of the tetragonal crystal field splitting E Z compared to that of the Hund's rule interaction J H in these systems. This gives evidence for the high-spin d 8 ground state of the undoped nickelates (i.e. J H >E Z ). It is suggested that the polarons in La 2-x Sr x NiO 4+δ can be seen as non

  16. Preparation of a ceramic superconductor from ultrafine particles by freeze-dry process in Ba-Y-Cu-O system

    International Nuclear Information System (INIS)

    Chen Zuyao; Qian Yitai; Wan Yanjian; Rong Jingfang; Zhang Han; Pan Guoqiang; Zhao Yong; Zhang Qirui

    1989-01-01

    Freeze-dry technique is first reported for preparing ceramic ultrafines. The single-phase complex oxide Ba 2 YCu 3 O/sub 9-δ/, a poly-crystallized compound, and ceramic superconductor have been synthesized successfully. The experimental results show that not only is the ceramic superconductor obtained uniform with fine particles and excellent superconductivity, but the conditions for solid reactions are relatively limited

  17. Influence of ion-rradiated SrTiO sub 3 on the properties of thin film oxide superconductors. [YBaCuO

    Energy Technology Data Exchange (ETDEWEB)

    Bordes, N; Cohen, M; Nastasi, M; Rollett, A D; Maggiore, C J [Los Alamos National Lab., NM (USA)

    1989-12-10

    The quality of high-temperature superconducting thin films is dependent on the structure of the substrate used. The present work examines the effects of radiation-damaged SrTiO{sub 3} substrates on the properties of Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} thin film superconductors. Prior to film deposition, single-crystal SrTiO{sub 3} substrates were cooled to 77 K and irradiated with 400 keV neon ions to doses of 1x10{sup 15} and 1x10{sup 16} ions cm{sup -2}. Following deposition the film/substrate couples were annealed in ''wet'' oxygen at either 850 or 900deg C. Films on substrates irradiated at high doses showed an increase in transition width from 2deg to 8deg and lowered transition temperature from 92 to 65 K relative to films on low dose and unirradiated substrates. These differences are discussed in terms of results obtained from high-energy and Rutherford backscattering and channeling experiments, scanning electron microscopy observations and X-ray diffraction data. (orig.).

  18. Electrical conductivity and chemical stability of BaCe0· 8− xAxGd0 ...

    Indian Academy of Sciences (India)

    ... K. BaCe0.7In0.1Gd0.2O3− and BaCe0.7Zr0.1Gd0.2O3− ceramics exhibit an excellent chemical stability against boiling water. Indium is a suitable doping element to promote the sintering densification and to enhance both electrical conductivity and chemical stability of Gd-doped BaCeO3 at operating temperatures.

  19. Supercurrents in HgBa{sub 2}CaCu{sub 2}O{sub 6+{delta}} and TlBa{sub 2}CaCu{sub 2}O{sub 7} epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Gapud, A.A.; Wu, J.Z.; Fang, L.; Yan, S.L.; Xie, Y.Y. [Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045-2151 (United States); Siegal, M.P.; Overmyer, D.L. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

    1999-06-01

    The availability of high-quality epitaxial thin films of HgBa{sub 2}CaCu{sub 2}O{sub 6+{delta}} (Hg-1212) and TlBa{sub 2}CaCu{sub 2}O{sub 7} (Tl-1212) with high critical current densities (J{sub c}) has made it possible to examine and compare the J{sub c} of these species. Results reveal that the J{sub c} of 1212 species have very similar temperature behavior at low fields, strongly suggesting that the 30 K shift in critical temperature (T{sub c}) induced by the exchange of Hg and Tl in the 1212 structure is due largely to a change in charge carrier density and/or electronic band structure. {copyright} {ital 1999 American Institute of Physics.}

  20. Melt processing of Bi-Ca-Sr-Cu-O superconductors

    International Nuclear Information System (INIS)

    Zanotto, E.D.; Cronin, J.P.; Dutta, B.

    1988-01-01

    Several Bi-Ca-Sr-Cu-O compositions were melted in Al/sub 2/O/sub 3/ or Pt crucibles at temperatures between 1050C and 1200C. As-quenched specimens crystallized from the upper surfaces, while the bottom layers were glassy. Glass formation was improved for higher Bi/sub 2/O/sub 3/ concentrations. The crystalline portions were highly conductive, while the glassy layers were insulating. Both did not show superconductivity down to 10K. Thermal treatment in air caused a dramatic effect on the electronic properties; and annealing at 865C for long periods converted the two types of specimens (previously glassy or crystalline) to superconductors, at least for one composition. Aluminum impurity (up to 8.6 atom. pct.) had no detectable effect on the transition temperatures, i.e., T/sub c/ 85K for all superconducting samples. The flake-like (Bi/sub 2/Ca/sub 1/Sr/sub 2/Cu/sub 2/) phase, reported by other authors, was responsible for superconductivity

  1. Magnetic fluctuations in La1.95Ba0.05CuO4

    DEFF Research Database (Denmark)

    Hayden, S.M.; Aeppli, G.; Mook, H.

    1991-01-01

    Neutron-scattering and resistivity experiments on single crystals of La1.95Ba0.05CuO4 are described. On warming to as high as 250 K, the correlation length does not change, and the temperature dependence of the generalized susceptibility chi(Q, omega) is due solely to the temperature dependence o...

  2. New Method of Preparation of Isomers of the (Ca0.1La0.9)(Ba1.6.5La0.35)Cu3Oy Superconductor with Predicted Maximal Tc

    International Nuclear Information System (INIS)

    Knizhnik, A.; Reisner, G.M.; Men, A.; Eckstein, Y.

    1998-01-01

    The 123 superconductor (Ca 0.1 La 0.9 )(Ba 1.6.5 La 0.35 )Cu 3 O y (c) has been prepared by the usual carbonate-oxide method. After oxygenation to the optimal oxygen doping of y=7.135, the maximal T c =57K. We prepared (c) also via reaction (1): 0.75La(La 0.25 Ba 1.75 )Cu 3 O 6.782 +0.25Ca 0.4 La 0.6 (La 0.65 Ba 1.35 )Cu 3 O 6.806 + 0.033O 2 (Ca 0. 1La 9 )(Ba 1.65 La 0.35 )Cu 3 ) 6.854 (1) The initial reagents are also superconductors. The first (a) has a maximal T c =57K, second (b) - 81K. In reference [1] we have shown that several isomers having the same general formula (c), may exist each having different ratios of the follow- ing possible unit cells: LaBa 2 Cu 3 O y , La(BaLa)Cu 3 O y , LaLa 2 Cu 3 O y , CaBa 2 Cu 3 O y , Ca(BaLa)Cu30 , CaLa2Cu30 . These isomers are formed at different temperatures of the preparation of (c) by carbonate-oxide method [1]. After the formation of compound (c) has been completed, further heating, even to higher temperatures, cannot change one isomer into another. Thus, there is no equilibrium between the (c) isomers and, if there also is no equilibrium in the cases of both isomers (a) and (b), then reaction (1) should not change the ratio of the unit cells. Each cell (i), which is present in (a) in concentration q i (a), should be present in (c) in concentration 0.75q i (a); analogously, each cell (i) which is present in (b) in concentration q i (b) should be present in (c) in concentration 0.25q i (b). According to the cluster component method, [2], T cmax = Σq i T i , where T i is T cmax of such a hypothetical sample, which contains cells (i) only. Thus the expected T cmax of (c), prepared via reaction (1), is: Σ0.75q i (a)T i + Σ0.25q i (b)T i = 0.75 x 57 + 0.25 x 81 = 63K, i.e. higher by 6 degrees than the T cmax of (c) prepared by the usual method. We studied reaction (1) via X-ray diffraction. XRD spectra showed that the intensity of the reagents peaks decrease with the time of the reaction and after 100 hours at 950 deg

  3. Device-quality tunnel junctions on the high Tc superconductor HgBa2CuO4+δ

    International Nuclear Information System (INIS)

    Zasadzinski, J.; Chen, J.; Romano, P.; Gray, K.E.; Wagner, J.L.; Hinks, D.G.

    1995-01-01

    SIN and SIS tunnel junction devices (e.g. photon detectors, logic elements) require quasiparticle characteristics that exhibit sharp current onsets at the gap voltage and very low sub-gap conductances. Progress is reported on the development of such junctions on High Tc cuprates using mechanical point contacts. In general, these contacts display the optimum characteristics that can be obtained from HTS native-surface tunnel barriers. Most cuprates display a sub-gap conductance which monotonically increases with voltage about the minimum value at zero bias. However, tunneling data of unusually high quality have been obtained for the recently discovered Hg-based cuprate, HgBa 2 CuO 4 (T c =96K). SIS' tunneling data using a Nb tip are presented which exhibit very low and flat sub-gap conductances and sharp conductance peaks as expected from a BCS density of states. These results are slightly improved over earlier published results with SIN junctions. Use of the experimental data to simulate the performance of a quasiparticle mixer demonstrates that noise temperatures approaching the quantum limit are possible for SIS and SIN mixers in the range 1-5 THz

  4. Ceramic high temperature superconductor levitating motor with laser commutator

    International Nuclear Information System (INIS)

    Roslan Abd Shukor; Lee Keng Heong

    1996-01-01

    The design of a magnetically levitating motor using a ceramic high temperature superconductor with laser commutator is discussed. A YBa sub 2 Cu sub 3 O sub 7-δ high temperature superconductor with 25 mm diameter and 6 mm thickness is used to levitate a Nd-Fe-B magnet (19.0 mm diameter and 4.8 mm thickness) which is attached symmetrically to a 150 mm long graphite rod. A smaller magnet (5.5 mm diameter and 2.0 mm thickness) is attached at each end of the rod with the appropriate poles arrangements. A suitable laser beam chopper is used to optically drive a solenoid which repels the smaller magnets thus driving the motor. A simple and efficient liquid nitrogen supply system is designed to cool the superconductor. The stability of the bearing is provided by the flux pinning in this type-II superconductor. Some characteristics of the motor are discussed

  5. Phonon anomalies in trilayer high-Tc cuprate superconductors

    International Nuclear Information System (INIS)

    Dubroka, Adam; Munzar, Dominik

    2004-01-01

    We present an extension of the model proposed recently to account for dramatic chAes below T c (anomalies) of some c-axis polarized infrared-active phonons in bilayer cuprate superconductors, that applies to trilayer high-T c compounds. We discuss several types of phonon anomalies that can occur in these systems and demonstrate that our model is capable of explaining the spectral chAes occurring upon entering the superconducting state in the trilayer compound Tl 2 Ba 2 Ca 2 Cu 3 O 10 . The low-temperature spectra of this compound obtained by Zetterer and coworkers display an additional broad absorption band, similar to the one observed in underdoped YBa 2 Cu 3 O 7-δ and Bi 2 Sr 2 CaCu 2 O 8 . In addition, three phonon modes are strongly anomalous. We attribute the absorption band to the transverse Josephson plasma resonance, similar to that of the bilayer compounds. The phonon anomalies are shown to result from a modification of the local fields induced by the formation of the resonance. The spectral chAes in Tl 2 Ba 2 Ca 2 Cu 3 O 10 are compared with those occurring in Bi 2 Sr 2 Ca 2 Cu 3 O 10 , reported recently by Boris and coworkers

  6. Plastic deformation of YBa2Cu3O7-x superconductor compound

    International Nuclear Information System (INIS)

    Torres V, G.; Moreno, J.E.

    1988-01-01

    The high temperature superconductor YBa 2 Cu 3 O 7-x shown a brittle behavior when deformed under ambient conditions. If a hydrostatic state of stress is imposed with a metal matrix, it is possible to induce exttended plastic deformations as a great as 200% were achieved using this method without loosing the superconductivity in the ceramic. The observed deformations mechanisms are similar to those observed in the superplastic metals and the boundary ceramic metal matrix was found to be highly coherent. This method opens a new technique that can be apllied in the manufacture of superconductor wire. (author) [pt

  7. Effect of double layer thickness on magnetoelectric coupling in multiferroic BaTiO3-Bi0.95Gd0.05FeO3 multilayers

    Science.gov (United States)

    Hohenberger, S.; Lazenka, V.; Temst, K.; Selle, S.; Patzig, C.; Höche, T.; Grundmann, M.; Lorenz, M.

    2018-05-01

    The effect of double-layer thickness and partial substitution of Bi3+ by Gd3+ is demonstrated for multiferroic BaTiO3–BiFeO3 2–2 heterostructures. Multilayers of 15 double layers of BaTiO3 and Bi0.95Gd0.05FeO3 were deposited onto (0 0 1) oriented SrTiO3 substrates by pulsed laser deposition with various double layer thicknesses. X-ray diffraction and high resolution transmission electron microscopy investigations revealed a systematic strain tuning with layer thickness via coherently strained interfaces. The multilayers show increasingly enhanced magnetoelectric coupling with reduced double layer thickness. The maximum magnetoelectric coupling coefficient was measured to be as high as 50.8 V cm‑1 Oe‑1 in 0 T DC bias magnetic field at room temperature, and 54.9 V cm‑1 Oe‑1 above 3 T for the sample with the thinnest double layer thickness of 22.5 nm. This enhancement is accompanied by progressively increasing perpendicular magnetic anisotropy and compressive out-of-plane strain. To understand the origin of the enhanced magnetoelectric coupling in such multilayers, the temperature and magnetic field dependency of is discussed. The magnetoelectric performance of the Gd3+ substituted samples is found to be slightly enhanced when compared to unsubstituted BaTiO3–BiFeO3 multilayers of comparable double-layer thickness.

  8. High temperature X-ray diffraction studies on HfO2-Gd2O3 system

    International Nuclear Information System (INIS)

    Panneerselvam, G.; Antony, M.P.; Ananthasivan, K.; Joseph, M.

    2016-01-01

    High temperature X-ray diffraction (HTXRD) technique is an important experimental tool for measuring thermal expansion of materials of interest. A series of solid solutions containing GdO 1.5 in HfO 2 ,Hf 1-y Gd y )O 2 (y = 0.15, 0.2, 0.3, 0.41 and 0.505) were prepared by solid state method. Structural characterization and computation of lattice parameter was carried out by using room temperature X-ray diffraction measurements. The room temperature lattice parameter estimated for (Hf 1-y Gd y )O 2 (y=0.15, 0.2, 0.3, 0.41 and 0.505) are 0.51714 nm, 0.51929 nm, 0.52359nm, 0.52789nm and 0.53241 nm, respectively. Thermal expansion coefficients and percentage linear thermal expansion of the HfO 2 -Gd 2 O 3 solid solutions containing 20 and 41 mol% GdO 1.5 were determined using HTXRD in the temperature range 298 to 1673K. The mean linear thermal expansion coefficients of the solid solutions containing 20 and 41 mol. %Gd are 11.65 x 10 -6 K -1 and 12.07 x 10 -6 K -1 , respectively. (author)

  9. Electronic structure and electron-phonon coupling in layered copper oxide superconductors

    International Nuclear Information System (INIS)

    Pickett, W.E.; Cohen, R.E.; Krakauer, H.

    1991-01-01

    Experimental data on the layered Cu-O superconductors seem more and more to reflect normal Fermi-liquid behavior and substantial correspondence with band structure predictions. Recent self-consistent, microscopic band theoretic calculations of the electronic structure, lattice instabilities, phonon frequencies, and electron-phonon coupling characteristics and strength for La 2 CuO 4 and YBa 2 Cu 3 O 7 are reviewed. A dominant feature of the coupling is a novel Madelung-like contribution which would be screened out in high density of states superconductors but survives in cuprates because of weak screening. Local density functional theory correctly predicts the instability of (La, Ba) 2 CuO 4 to both the low-temperature orthorhombic phase (below room temperature) and the lower-temperature tetragonal phase (below 50 K). (orig.)

  10. Structure, resistivity, critical field, specific-heat jump at Tc, Meissner effect, a.c. and d.c. susceptibility of the high-Tc superconductor YBa2Cu3O7

    International Nuclear Information System (INIS)

    Junod, A.; Bezinge, A.; Graf, T.

    1987-01-01

    YBa 2 Cu 3 O 7 superconductors with inductive transitions as narrows as 0.45 K above 90 K were synthetized. Samples were characterized by thermogravimetry, differential thermal analysis, X-ray and neutron diffraction. The structure is characterized by a two-dimensional Cu-O network with square-pyramidal and square-planar coordinated Cu atoms. Results show a clear metallic behaviour of the resistivity. An orbital critical field as high as 300 T is extrapolated. Meissner flux expulsion up to 40% is observed. Small amounts of magnetic Cu 2+ ions are correlated with the presence of the impurity phase BaCuO 2 . The Pauli susceptibility and the specific-heat jump at T c are consistent with γ ≅ 2mJ/(K 2 gat) (9mJ/(K 2 mole-Cu)), neglecting all renormalizations

  11. Proximity effect in YBa2Cu3O7/Y0.6Pr0.4Ba2Cu3O7/YBa2Cu3O7 junctions

    International Nuclear Information System (INIS)

    Polturak, E.; Koren, G.; Cohen, D.; Aharoni, E.; Deutscher, G.

    1991-01-01

    We report critical-current measurements in all high-T c superconducting-normal-superconductor junctions using Y 0.6 Pr 0.4 Ba 2 Cu 3 O 7 (with T cN =40 K) as the normal metal. Above T cN , we find a clear exponential dependence of I c on the thickness of the barrier which is characteristic of the proximity effect. The order-parameter decay length is about 120 A for T>60 K, and it diverges as T cN is approached. We estimate that ξ 0 for this material is 80±25 A

  12. The high temperature superconductor YBa2Cu3O7-δ: symmetry of the order parameter, and gradiometers for biomagnetic applications

    International Nuclear Information System (INIS)

    Kouznetsov, Konstantin A.

    1999-01-01

    The cuprate YBa 2 Cu 3 O 7-δ is the material that drives the majority of the technological applications of high transition temperature (Tc) superconductors, particularly in the area of superconducting electronics. Despite the widespread use of high-Tc superconducting materials in a variety of applications, the nature of the superconducting state in these materials remains unknown since their discovery more than a decade ago. Many properties of the high-Tc superconductors are determined by their order parameter, which is a wavefunction describing the superconducting condensate. The symmetry of the order parameter in cuprates has been the subject of intensive investigation, leading to conflicting sets of results. Some experiments supported conventional, s-wave symmetry of the order parameter, while others indicated an unconventional, d-wave symmetry. The first part of this thesis is an experimental study of the symmetry of the order parameter in YBa 2 Cu 3 O 7-δ . A new class of phase sensitive experiments is described that involve Josephson tunneling along the c-axis of twinned crystals of YBa 2 Cu 3 O 7-δ . These experiments showed that an s-wave component must reverse sign across the twin boundary, providing direct evidence for a mixed, s+d symmetry of the order parameter in YBa 2 Cu 3 O 7-δ , and thereby reconciling two conflicting sets of previous findings and establishing the dominant d-wave pairing symmetry. The second part of the thesis focuses on practical applications of YBa 2 Cu 3 O 7-δ in superconducting electronics. The authors introduce a novel Superconducting Quantum Interference Device (SQUID) gradiometer. The principle of operation of these long baseline high-T c SQUID gradiometers is based on the inductive coupling of the input coil of a planar flux transformer to the pickup up loop of a directly coupled magnetometer. The long baseline of the gradiometer, 48 mm, and the intrinsic. Balance of better than 1 part in 100 make it an ideal candidate

  13. X-ray scattering study of the temperature dependence of the structure of the high Tsub(c) superconductor Lasub(1.8)Srsub(0.2)CuO4

    International Nuclear Information System (INIS)

    Held, G.A.; Horn, P.M.; Tsuei, C.C.; LaPlaca, S.J.; Bednorz, J.G.; Mueller, K.A.

    1987-01-01

    We present data from powder scans of the High Tsub(c) (approx. 40 K) superconductor Lasub(1.8)Srsub(0.2)CuO 4 as a function of temperature from room temperature to 10 K. We observe a K 2 NiF 4 -type structure, with no evidence for a structural phase transition or anomalous changes in the lattice constants. For T > or approx. 190 K the values of the thermal expansion constants are not unusual for a metal oxide. (author)

  14. Electronic structure of PrBa2Cu3O7

    International Nuclear Information System (INIS)

    Singh, D.J.

    1994-01-01

    Electronic-structure calculations, within the local spin density approximation (LSDA), are reported for PrBa 2 Cu 3 O 7 . Significant charge transfer from the Pr ions to both the CuO 2 planes and the chains is found relative to YBa 2 Cu 3 O 7 . This supports hole depletion explanations for the insulating character of PrBa 2 Cu 3 O 7 . The LSDA electronic structure shows a prominent ''ridge'' Fermi surface analogous to that in YBa 2 Cu 3 O 7 , but broader. It is proposed that high-resolution positron measurements of this width may provide a useful test of hole depletion models

  15. Performance of ultrahigh resolution electron microscope JEM-4000EX and some applications of high Tc superconductors

    International Nuclear Information System (INIS)

    Honda, T.; Ibe, K.; Ishida, Y.; Kersker, M.M.

    1989-01-01

    The high resolution electron microscope is powerful for modern materials science because of its direct observation capability for the atomic structure of materials. the JEM-4000EX, a 400 kV accelerating voltage electron microscope whose objective lens has a 1 mm spherical aberration coefficient, has a 0.168 nm theoretical resolving power. Using this microscope, atomic structure images of high Tc superconductor such as Y-Ba-Cu-O, Bi-Ca-Sr-Cu-O and Tl-Ca-Ba-Cu-O are reported

  16. Influence of Zr and Ce doping on electromagnetic properties of (Gd,Y)-Ba-Cu-O superconducting tapes fabricated by metal organic chemical vapor deposition

    International Nuclear Information System (INIS)

    Selvamanickam, V.; Chen, Y.; Xie, J.; Zhang, Y.; Guevara, A.; Kesgin, I.; Majkic, G.; Martchevsky, M.

    2009-01-01

    (Gd,Y)Ba 2 Cu 3 O x tapes have been fabricated by metal organic chemical vapor deposition (MOCVD) with Zr-doping levels of 0-15 mol.% and Ce doping levels of 0-10 mol.% in 0.4 μm thick films. The critical current density (J c ) of Zr-doped samples at 77 K, 1 T applied in the orientation of H -parallel c is found to increase with Zr content and shows a maximum at 7.5% Zr doping. The 7.5% Zr-doped sample exhibits a critical current density (J c ) of 0.95 MA/cm 2 at H -parallel c which is more than 70% higher than the J c of the undoped sample. The peak in J c at H -parallel c is 83% of that at H -parallel a-b in the 7.5% Zr-doped sample which is more than twice as that in the undoped sample. Superconducting transition temperature (T c ) values as high as about 89 K have been achieved in samples even with 15% Zr and 10% Ce. Ce-doped samples with and without Ba compensation are found to exhibit substantially different J c values as well as angular dependence characteristics.

  17. Influence of Zr and Ce doping on electromagnetic properties of (Gd,Y)-Ba-Cu-O superconducting tapes fabricated by metal organic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Selvamanickam, V., E-mail: selva@uh.ed [Department of Mechanical Engineering and Texas Center for Superconductivity, University of Houston, 4800 Calhoun Rd., Houston, TX 77204-4006 (United States); Chen, Y.; Xie, J. [SuperPower Inc., 450 Duane Ave., Schenectady, NY 12304 (United States); Zhang, Y.; Guevara, A.; Kesgin, I.; Majkic, G. [Department of Mechanical Engineering and Texas Center for Superconductivity, University of Houston, 4800 Calhoun Rd., Houston, TX 77204-4006 (United States); Martchevsky, M. [SuperPower Inc., 450 Duane Ave., Schenectady, NY 12304 (United States)

    2009-12-01

    (Gd,Y)Ba{sub 2}Cu{sub 3}O{sub x} tapes have been fabricated by metal organic chemical vapor deposition (MOCVD) with Zr-doping levels of 0-15 mol.% and Ce doping levels of 0-10 mol.% in 0.4 mum thick films. The critical current density (J{sub c}) of Zr-doped samples at 77 K, 1 T applied in the orientation of H -parallel c is found to increase with Zr content and shows a maximum at 7.5% Zr doping. The 7.5% Zr-doped sample exhibits a critical current density (J{sub c}) of 0.95 MA/cm{sup 2} at H -parallel c which is more than 70% higher than the J{sub c} of the undoped sample. The peak in J{sub c} at H -parallel c is 83% of that at H -parallel a-b in the 7.5% Zr-doped sample which is more than twice as that in the undoped sample. Superconducting transition temperature (T{sub c}) values as high as about 89 K have been achieved in samples even with 15% Zr and 10% Ce. Ce-doped samples with and without Ba compensation are found to exhibit substantially different J{sub c} values as well as angular dependence characteristics.

  18. Hydrostatic pressure dependence of the superconducting transition temperature of HgBa2CaCu2O6+δ and HgBa2Ca2Cu3O8+δ

    International Nuclear Information System (INIS)

    Klehe, A.K.; Schilling, J.S.

    1994-02-01

    The dependence of the superconducting transition temperature T c (P) on purely hydrostatic pressure to 0.9 GPa has been determined in ac susceptibility studies in a He-gas pressure system for optimally doped ceramic samples of HgBa 2 CaCu 2 O 6+δ and HgBa 2 Ca 2 Cu 3 O 8+δ with superconducting transitions at T c (0) ≅ 126.6 K and 133.9 K, respectively. T c increases reversibly under hydrostatic pressure at the rates, d T c /dP ≅ +1.80 ± 0.06 K/GPa and +1.71 ± 0.05 K/GPa, respectively. Within experimental error, these values are the same as found previously for optimally doped single-layered HgBa 2 CuO 4+δ , where d T c /dP ≅ +1.72 ± 0.05 K/GPa. Remarkably, the logarithmic volume derivative of T c is nearly identical for all three compounds, dln T c /dlnV ≅ -1.20 ± 0.05, even though the bulk modulus differs by more than 30%. This provides strong evidence that a common mechanism is responsible for the pressure dependence of the superconducting state in all three compounds

  19. Mechanical design of a synchronous rotating machines with Gd-Ba-Cu-O HTS bulk pole-field magnets operated by a pulsed-field magnetization with armature copper coils

    Energy Technology Data Exchange (ETDEWEB)

    Matsuzaki, H [Department of Electronic and Mechanical Engineering, Tokyo University of Marine Science and Technology, Koto-ku, Tokyo 135-8533 (Japan); Kimura, Y [Department of Electronic and Mechanical Engineering, Tokyo University of Marine Science and Technology, Koto-ku, Tokyo 135-8533 (Japan); Ohtani, I [Department of Electronic and Mechanical Engineering, Tokyo University of Marine Science and Technology, Koto-ku, Tokyo 135-8533 (Japan); Morita, E [Department of Electronic and Mechanical Engineering, Tokyo University of Marine Science and Technology, Koto-ku, Tokyo 135-8533 (Japan); Ogata, H [Department of Electronic and Mechanical Engineering, Tokyo University of Marine Science and Technology, Koto-ku, Tokyo 135-8533 (Japan); Izumi, M [Department of Electronic and Mechanical Engineering, Tokyo University of Marine Science and Technology, Koto-ku, Tokyo 135-8533 (Japan); Ida, T [Department of Electronic Control Engineering, Hiroshima National College of Maritime Technology, Hiroshima 725-0231 (Japan); Sugimoto, H [Department of Electrical and Electronic Engineering, Fukui University, Fukui 910-8507 (Japan); Miki, M [Kitano Seiki Co. Ltd., Ohta-ku, Tokyo 143-0024 (Japan); Kitano, M [Kitano Seiki Co. Ltd., Ohta-ku, Tokyo 143-0024 (Japan)

    2006-06-01

    We studied a high-temperature superconducting (HTS) synchronous motor assembled with melt-textured Gd-Ba-Cu-O bulk pole-field magnets. The structure of a HTS motor is an axial gap type with neither brushes/slip rings nor iron core. The specific feature is that the rotor pole-field magnets of bulk are magnetized with pulsed current flow through vortex-type armature copper windings. The rotor pole bulks and armature coils are cooled down with liquid nitrogen. Cooling and magnetization of bulk pole field magnets are performed inside of the rotor. The trapped peak magnetic field of more than 0.5 T of the bulk magnets provided the motor performance of 3.1 kW with 720 rpm. In order to attain high output, single rotor plate with 8 bulks was substituted with a twinned rotor plates with 16 bulks together with triple layer armature units. We report on the test results and performance of the present twinned rotor-type HTS synchronous motor.

  20. Charge redistribution and properties of high-temperature superconductors

    International Nuclear Information System (INIS)

    Khomskii, D.I.; Kusmartsev, F.V.

    1992-01-01

    We show that in high-T c superconductors (HTSC) with two groups of electrons (e.g., holes in CuO 2 planes and in a ''reservoir'') there should exist a charge redistribution with the temperature: the hole concentration N h in ''active'' superconducting CuO 2 planes increases below T c . This effect may explain structural changes such as the shift of the apical oxygen atom, anomalous thermal expansion, the shift of nuclear quadrupole resonance lines, the change of the positron lifetime, and the modification of the ion channeling below T c . Some other possible consequences of the charge redistribution (the modification of the temperature dependence of a gap Δ and of the ratio 2Δ 0 /T c , the phenomena at a contact of HTSC with normal metals and semiconductors) are discussed

  1. Annihilation of positrons with the electrons of chemical bonds of the superconducting CuO-polyhedrons in the HTSC materials

    International Nuclear Information System (INIS)

    Arutyunov, N.Yu.; Trashchakov, V.Yu.

    1989-01-01

    Angular distribution parameters of annihilation photon pairs emitted from R-Ba 2 Cu 3 O 7-x (x≤0.2; R=Y, Nd, Lu) specimens after injection and subsequent annihilation of positrons in them. It is shown that annihilation of thermalized positrons proceeds advantageously with electrons of chemical bonds of O(4)-Cu(I)-O(I) polyhedrons in R-Ba-Cu-O oxides. In an orthorhombic phase positrons are mostly delocalized in rows of ordered stoichiometric vacancies. The result obtained provides to recommend the methods of positron diagnostics for studying parameters of electron state density in superconducting structural groups of high-temperature superconductors. 2 refs.; 1 fig

  2. Investigation of thin films, heterostructures and devices of ceramic superconductors by means of high-resolution electron microscopy

    International Nuclear Information System (INIS)

    Jia Chunlin.

    1993-08-01

    In this thesis a systematic study of the microstructure of YBa 2 Cu 3 O 7 thin films is presented by means of high-resolution electron microscopy (HREM). Most of the efforts are focused on the characterization of heterostructures of superconducting YBa 2 Cu 3 O 7 and non-superconducting PrBa 2 Cu 3 O 7 and on YBa 2 Cu 3 O 7 films deposited on step-edge substrates. These specially designed structures exhibit a great potential for the electronic application of high-Tc superconductors and for the investigation of the basic electric properties of the YBa 2 Cu 3 O 7 superconductor. (orig.) [de

  3. Enhanced and uniform in-field performance in long (Gd, Y)-Ba-Cu-O tapes with zirconium doping fabricated by metal-organic chemical vapor deposition

    International Nuclear Information System (INIS)

    Selvamanickam, V; Guevara, A; Zhang, Y; Kesgin, I; Xie, Y; Carota, G; Chen, Y; Dackow, J; Zhang, Y; Zuev, Y; Cantoni, C; Goyal, A; Coulter, J; Civale, L

    2010-01-01

    The influence of Zr doping in (Gd, Y)-Ba-Cu-O ((Gd, Y)BCO) tapes made by metal-organic chemical vapor deposition has been studied with a specific objective of uniform and reproducible enhancement in in-field critical current (I c ) over long lengths. 50 m long tapes with 7.5 and 10 at.% Zr doping in 1 μm thick (Gd, Y)BCO films have been found to exhibit a sharply enhanced peak in I c in the orientation of field parallel to the c-axis and retain 28% of their self-field I c value at 77 K and 1 T. BaZrO 3 (BZO) nanocolumn density in the cross-sectional microstructure was found to increase with increasing Zr addition. The end segments of the 50 m long tapes were found to display nearly identical angular dependence of critical current at 77 K and 1 T, indicative of the uniformity in in-field performance over this length. A 610 m long tape was fabricated with 10% Zr doping and a 130 m segment showed a 3.2% uniformity in critical current measured every meter in the orientation of B || c-axis. A retention factor of 36% of the zero-field I c value measured at 0.52 T over the 130 m is consistent with that obtained in short samples.

  4. Enhanced and uniform in-field performance in long (Gd, Y)-Ba-Cu-O tapes with zirconium doping fabricated by metal-organic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Selvamanickam, V; Guevara, A; Zhang, Y; Kesgin, I [Texas Center for Superconductivity and Department of Mechanical Engineering, University of Houston, Houston, TX 77059 (United States); Xie, Y; Carota, G; Chen, Y; Dackow, J [SuperPower Incorporated, 450 Duane Avenue Schenectady, NY 12304 (United States); Zhang, Y; Zuev, Y; Cantoni, C; Goyal, A [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Coulter, J; Civale, L [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2010-01-15

    The influence of Zr doping in (Gd, Y)-Ba-Cu-O ((Gd, Y)BCO) tapes made by metal-organic chemical vapor deposition has been studied with a specific objective of uniform and reproducible enhancement in in-field critical current (I{sub c}) over long lengths. 50 m long tapes with 7.5 and 10 at.% Zr doping in 1 {mu}m thick (Gd, Y)BCO films have been found to exhibit a sharply enhanced peak in I{sub c} in the orientation of field parallel to the c-axis and retain 28% of their self-field I{sub c} value at 77 K and 1 T. BaZrO{sub 3} (BZO) nanocolumn density in the cross-sectional microstructure was found to increase with increasing Zr addition. The end segments of the 50 m long tapes were found to display nearly identical angular dependence of critical current at 77 K and 1 T, indicative of the uniformity in in-field performance over this length. A 610 m long tape was fabricated with 10% Zr doping and a 130 m segment showed a 3.2% uniformity in critical current measured every meter in the orientation of B || c-axis. A retention factor of 36% of the zero-field I{sub c} value measured at 0.52 T over the 130 m is consistent with that obtained in short samples.

  5. Enhanced and Uniform in-Field Performance in Long (Gd,Y)-Ba-Cu-O Tapes with Zirconium Doping Fabricated by Metal Organic Chemical Vapor Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Selvamanickam, V. [SuperPower Incorporated, Schenectady, New York; Guevara, A. [University of Houston, Houston; Zhang, Y. [University of Houston, Houston; Kesign, I. [University of Houston, Houston; Xie, Y. Y. [SuperPower Incorporated, Schenectady, New York; Carota, G. [SuperPower Incorporated, Schenectady, New York; Chen, Y. [SuperPower Incorporated, Schenectady, New York; Dackow, J. [SuperPower Incorporated, Schenectady, New York; Zhang, Yifei [ORNL; Zuev, Yuri L [ORNL; Cantoni, Claudia [ORNL; Goyal, Amit [ORNL; Coulter, J. [Los Alamos National Laboratory (LANL); Civale, L. [Los Alamos National Laboratory (LANL)

    2010-01-01

    The influence of Zr doping in (Gd, Y)-Ba-Cu-O ((Gd, Y)BCO) tapes made by metal-organic chemical vapor deposition has been studied with a specific objective of uniform and reproducible enhancement in in-field critical current (I{sub c}) over long lengths. 50 m long tapes with 7.5 and 10 at.% Zr doping in 1 {mu}m thick (Gd, Y)BCO films have been found to exhibit a sharply enhanced peak in I{sub c} in the orientation of field parallel to the c-axis and retain 28% of their self-field I{sub c} value at 77 K and 1 T. BaZrO{sub 3} (BZO) nanocolumn density in the cross-sectional microstructure was found to increase with increasing Zr addition. The end segments of the 50 m long tapes were found to display nearly identical angular dependence of critical current at 77 K and 1 T, indicative of the uniformity in in-field performance over this length. A 610 m long tape was fabricated with 10% Zr doping and a 130 m segment showed a 3.2% uniformity in critical current measured every meter in the orientation of {beta} {parallel} c-axis. A retention factor of 36% of the zero-field I{sub c} value measured at 0.52 T over the 130 m is consistent with that obtained in short samples.

  6. Anomalies of temperature dependence of the upper critical magnetic field of GdBa2Cu3O7-x and their relation with layered crystal structure

    International Nuclear Information System (INIS)

    Anshukova, N.V.; Veselago, V.G.; Golovashkin, A.I.

    1989-01-01

    Temperature dependence of upper critical field H c2 (T) near T c was investigated on polycrystal GdBa 2 Cu 3 O 7-x . The resistive superconductive transitions were measured in magnetic fields up to 15 T. We observed a magnetic-field induced broadening of transition and an appearance of H c2 (T) nonlinearity near T c and explained such effects by the influence of individual grains H c2 anisotropy on the base of the percolation model. Estimated are slopes: for magnetic field along superconductive layers -dH c2 parallel /dT≅ 7T/K and for field across layers -dH c2 tr /dT=0.2 T/K. It was found that H c2 (T)-curves display anomalies in a break form, which were not explained in the percolation model. The across coherence length ξ tr (T) obtained from values of the slopes was comparable with distance d between two superconductive layers. So we think that in this situation a fracture on the H c2 (T)-curves may be explained by the appearance of electronic density nonuniformity and it is precursor of crossover to two-dimensional superconductivity

  7. Physical-chemical and technological aspects of the preparation of think layers of the high temperature superconductors Bi-Sr-Ca-Cu-O by method of metal organic vapour phase epitaxy

    International Nuclear Information System (INIS)

    Stejskal, J.; Nevriva, M.; Leitner, J.

    1995-01-01

    The method of metal organic vapour phase epitaxy (MO VPE) was used for preparation of think layers of the high temperature superconductors Bi-Sr-Ca-Cu-O. The suitable chemical precursors (β-diketonates) on the literature data and of the own thermodynamic calculations were selected. The optimal thermodynamic data and thermodynamic stability of the prepared samples were determined

  8. The defect structure of ceramic high Tc superconductors

    International Nuclear Information System (INIS)

    Van Tendeloo, G.; Amelinckx, S.; Zandbergen, H.W.; Verwerft, M.

    1989-01-01

    In this paper an overview is given of electron microscopy studies on the different ceramic superconductors: YBa 2 Cu 3 O 7 , Bi(Tl)-Sr(Ba)- Ca-Cu-O and Pb 2 Sr 2 Y 0.5 Ca 0.5 Cu 3 O x . Planar defects in these materials play an important role in the superconducting properties. Their structural characteristics are discussed

  9. Growth and characterization of high-Tc Y1Ba2Cu3O7-x superconducting thin films by chemical vapor deposition

    International Nuclear Information System (INIS)

    Feng, A.

    1992-01-01

    In chapter I, the current status of high-Tc superconductors (especially Y 1 Ba 2 Cu 3 O 7-x ), their microstructures and their unique physical properties are reviewed. An introduction to the potential and importance of those high-Tc superconductors in practical applications, especially for the application of YBCO thin films in microelectronics, is given. A general description of the common YBCO thin film fabrication and characterization techniques is also presented in this first chapter. Chapter II describes a new CVD process, temperature-controlled chemical vapor deposition (TC-CVD) for the growth of YBCO superconducting thin films on substrates of practical importance, such as sapphire (Al 2 O 3 ) and on substrates of lattice matched perovskite-type single crystals, such as LaAlO 3 . In order to verify the viability of this new CVD process the qualities of YBCO superconducting thin films were examined by various characterization methods, such as resistivity vs. temperature (R vs. T), scanning electron microscopy (SEM), X-ray diffraction (XRD), and magnetic susceptibility (x) measurements. Chapter III deals with the effect of substrate temperature on the properties of YBCO thin films made by TC-CVD. The principle objective of this study is to raise the transition temperature and critical current densities of CVD YBCO superconducting thin films. Understanding the relations between YBCO film growth process and varying substrate temperatures proved to be crucial in reaching this goal. The authors present the characterization results of YBCO thin films produced by different temperature schemes, to illustrate the importance of varying substrate temperature during the film growth. In chapter IV, the Rutherford backscattering (RBS) channeling technique is described. They have used RBS channeling to characterize the epitaxial YBCO thin film's crystallinity and lattice alignment. Transmission electron microscopy studies are also included

  10. Real-time observation of growth and orientation of Sm-Ba-Cu-O phases on a Sm-211 whisker substrate by high-temperature optical microscopy

    Czech Academy of Sciences Publication Activity Database

    Sun, J.L.; Huang, Y.B.; Cheng, L.; Yao, X.; Lai, Y.J.; Jirsa, Miloš

    2009-01-01

    Roč. 9, č. 2 (2009), 898-902 ISSN 1528-7483 R&D Projects: GA ČR GA202/08/0722 Institutional research plan: CEZ:AV0Z10100520 Keywords : high-temperature optical microscopy * growth and orientation of Sm-Ba-Cu-O phases * Sm-211 whisker substrate Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 4.162, year: 2009

  11. Transition conductivity study of high temperature superconductor compounds: the role of fluctuations; Etude de la transition resistive sur des composes supraconducteurs a haute temperature critique le role des fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Pagnon, V

    1991-04-01

    This memory subject is the transition conductivity study of high temperature superconductors in corelation with their anisotropy. Systematic conductivity measurements were made on YBaCuO and BaSrCaCuO in relation with temperature from 4.2 K to 1200 K, and with a magnetic field up to 8 T in several directions. Oxygen order has an effect on the characteristics at YBaCuO transition conductivity. The activation energy for oxygen absorption is about 0.5eV. One method of analysis of the conductivity fluctuations about the transition temperature is proposed. Two separate rates are noticeable in YBaCuO compound. The 3 D fluctuations rate in the immediate neighbourghood of the transition lets place to the 2 D fluctuations rate at high temperature. Transitions temperatures governing each rate are different, that`s incompatible with the formula proposed by Lawrence and Doniach. On the other hand, the analogy with quasi-2 D magnetic systems seems more relevant. A magnetic field application or a lowering of oxygen concentration removes the 3 D fluctuations rate. Non ohmic effects observed at the transition conductivity foot are analysis as a non-linear 2 D excitation manifestation of the supraconductive phase. Finally, by measurements on strontium doped YBaCuO crystals, we confirm a metal-insulator transition along the C-Axe when oxygen concentration reduces. This is connected with the specific heat jump. All these results uplighten the fundamental bidimensional character of high transition temperature superconductivity.

  12. Current-carrying capacity dependence of composite Bi2Sr2CaCu2O8 superconductors on the liquid coolant conditions

    International Nuclear Information System (INIS)

    Romanovskii, V R; Watanabe, K; Awaji, S; Nishijima, G

    2006-01-01

    The thermal runaway conditions of the composite Bi 2 Sr 2 CaCu 2 O 8 superconductor cooled by liquid helium or liquid hydrogen are compared. The study based on the static analysis of thermoelectric modes was made when the volume fraction of the superconductor in a composite was varied. Some specific trends underlying the onset of thermal runaway in superconducting composites cooled by liquid coolants are discussed. It is stated that the operating modes of superconducting composites may be characterized by stable states during which the current-carrying capacity of a superconductor is not effectively used even with a high amount of superconductor in the composite. These states are possible due to the corresponding temperature variation of the resistivities of the matrix and the superconductor in the high operating temperature range. They have to be considered in experiments when the critical current of a superconductor is determined or when the optimal stable operating modes of the current-carrying elements based on the Bi 2 Sr 2 CaCu 2 O 8 superconductor, which is cooled by liquid coolant, are defined

  13. The superconductor (Tl,Hg,Ca)2(Ba,Sr)2(Ca,Sr,Tl)Cu2O7.6

    International Nuclear Information System (INIS)

    Valldor, M.; Bryntse, I.; Morawski, A.

    2002-01-01

    In the title 2212-type superconductor (thallium mercury calcium barium strontium copper oxide), which contains both Tl and Hg in the charge reservoir (CR), Sr is located at both alkali-earth (AE) metal sites. Ca enters the CR at the same time as Tl shares the smaller AE site, which increases the apical Cu-Cu distance significantly. The structure causes the superconducting Cu-O layers to become significantly puckered. (orig.)

  14. The complex ac susceptibility of superconducting Y-Ba-CuO thin film and bulk samples

    International Nuclear Information System (INIS)

    Lobotka, P.; Goemoery, F.

    1988-01-01

    Complex ac susceptibility measurements as function of temperature on Y-Ba-CuO superconductors are reported. A strong dependence of the susceptibility curves on the ac field magnitude and little influence of the superimposed dc field are observed on both, thin film and bulk samples. The susceptibilities of these materials are frequency independent in the range 30 to 7200 Hz what demonstrates the negligible role of eddy currents. A second peak in the imaginary part of susceptibility is observed in the bulk sample at higher levels of ac field. This implies the existence of another component in the sample with higher T c and lower losses. (author)

  15. Atomic ordering of the fluorine dopant in the $HgBa_{2}CuO_{4+\\delta}high-T_{c}$ superconductor

    CERN Document Server

    Correia, João Guilherme; Araújo, João Pedro; Bordet, P; Haas, Heinz; Le Floc'h, S; Lopes, A M L; Rita, E; Carvalho-Soares, João

    2005-01-01

    Lattice sites and collective ordering of fluorine atoms in oxygen- reduced samples of HgBa/sub 2/CuO/sub 4/ were investigated with the perturbed angular correlation technique by measuring the electric field gradients induced at /sup 199m/Hg nuclei. The experimental data were interpreted with the help of ab initio calculations of charge distributions for different fluorine configurations in Hg/sub m/Ba /sub 2m/Cu/sub m/O/sub 4m/F/sub n/, supercells. Internal parameters were allowed to relax, to cancel residual atomic forces due to the dopant. The experimental results show clearly that fluorine occupies only the center of the mercury mesh. For a fluorine content delta F>~0.35 the best agreement with theoretical data is obtained under the assumption that fluorine shows a tendency toward ordering along interstitial rows parallel to a, b. In conformity with experimental data from diffraction techniques the calculations show elongations of the O(2)-Hg-O(2) dumbbell and barium shifts towards the fluorine atoms as ef...

  16. Positron annihilation studies on high temperature superconductors

    International Nuclear Information System (INIS)

    Sundar, C.S.; Bharathi, A.

    1996-01-01

    A survey of the positron annihilation studies on high temperature superconductors (HTSC), with results drawn mainly from our work, is presented. These include results of the studies on the temperature dependence of positron lifetime across T c , which have been carried out in the whole gamut of oxide superconductors. These experimental results are discussed in conjunction with the results of theoretically calculated positron density distribution, and it is shown that the observed temperature dependence of lifetime is intimately linked to the probing of the Cu-O network by the positrons. Results on the investigation of oxygen defects, which play a crucial role in HTSC, are presented. The most significant contribution of positrons to HTSC relates to the investigation of Fermi surface and the results of these studies, drawn from literature, are indicated. Some of our recent results in other novel superconducting materials, viz., the fullerenes and borocarbides are also presented. (author). 69 refs., 15 figs

  17. Atomic hydrogen effects on high-Tc superconductors

    International Nuclear Information System (INIS)

    Frantskevich, N.V.; Ulyashin, A.G.; Alifanov, A.V.; Stepanenko, A.V.; Fedotova, V.V.

    1999-01-01

    The atomic hydrogen effects on the properties of bulk high-temperature superconductors were investigated. It is shown that the insertion of the atomic hydrogen into the bulk of these materials from a DC plasma leads to the increase of the critical current density J c for YBaCuO(123) as well as for BiSrCaCuO(2223) high-temperature superconductors. It is found that the hydrogenation of the He implanted samples with following annealing leads to the optically detected blistering on the surface. It means that the textured thin subsurface layers of high-temperature superconductors can be formed by this method. The improvement of superconductivity by atomic hydrogen can be explained by the passivation of dangling bonds and defects on grain boundaries of these materials

  18. Raman spectroscopic investigation of superconducting YBa2Cu3O7/sub -//sub x/, semiconducting YBa2Cu3O6/sub +//sub x/, and possible impurity phases

    International Nuclear Information System (INIS)

    Mascarenhas, A.; Geller, S.; Xu, L.C.; Katayama-Yoshida, H.; Pankove, J.I.; Deb, S.K.

    1988-01-01

    A Raman spectroscopic investigation of specimens of superconducting YBa 2 Cu 3 O/sub 7-//sub x/ and of the possible impurity phases YBa 2 Cu 3 O/sub 6+//sub x/ (semiconductor), Y 2 BaCuO 5 , Y 2 Cu 2 O 5 , BaCuO 2 , CuO, Y 2 O 3 , and BaCO 3 indicates that in the range 100--700 cm -1 , there are six characteristic lines belonging to the superconductor. At 13 K, these lines are at 150, 338, 441, 507, 590, and 644 cm -1 . Comparison of the Raman spectra of the superconductor and the semiconductor indicates a mode stiffening of the pair at 338 and 441 cm -1 , but a mode softening of the pair at 507 and 590 cm -1 . A factor group analysis leads to a tentative assignment of the Raman and infrared allowed modes

  19. Cu k-edge studies of the charge carries in Th-doped cuprate system R2-xThxCuO4-δ (R = Nd, Sm and Gd)

    International Nuclear Information System (INIS)

    Liang, G.; Yi, Y.; Jardim, R.F.; Wang, L.V.

    1999-01-01

    To further study the charge carrier concentration in electron doped cuprate superconductors, a systematic x-ray absorption near edge structure (XANES) measurement has been carried out on Th-doped superconductor system R 2-x Th x CuO 4-δ (R = Nd, Sm, and Gd). The XANES results show that, similar to the Ce-doped compounds, while the intensity of the Cu 1+ 4p π feature increase with the increase of the Th doping level x, the intensities of the Cu 2+ 4p π and 4p σ features decreases. This clearly indicates that the electrons doped by the Th atoms are injected into the local Cu 3d-orbitals. The normalized Cu 1+ 4p π intensity data show that the Cu 1+ concentration in the Th-doped compound series with different R-elements is linearly proportional to the Th doping-level x. The data suggest that both Ce and Th donate the same fraction of electrons into the Cu sites

  20. Systematics of c-axis phonons in the thallium- and bismuth-based cuprate superconductors

    NARCIS (Netherlands)

    Tsvetkov, A.A.; Dulic, Diana; Marel, D. van der; Damascelli, A.; Kaljushnaia, G.A.; Gorina, J.I.; Senturina, N.N.; Kolesnikov, N.N.; Ren, Z.F.; Wang, J.H.; Menovsky, A.A.; Palstra, T.T.M.

    1999-01-01

    We present grazing incidence reflectivity measurements in the far-infrared region at temperatures above and below Tc for a series of thallium- (Tl2Ba2CuO6, Tl2Ba2CaCu2O8) and bismuth- (Bi2Sr2CuO6, Bi2Sr2CaCu2O8, and Bi2-xPbxSr2CaCu2O8) based cuprate superconductors. From the spectra, which are

  1. Effect of oxygen annealing on magnetic performance of (Nd,Eu,Gd)Ba.sub.2./sub.Cu.sub.3./sub.O.sub.y./sub. with a lamelar pinning nanostructure

    Czech Academy of Sciences Publication Activity Database

    Jirsa, Miloš; Rameš, Michal; Muralidhar, M.; Diko, P.

    2009-01-01

    Roč. 153, č. 1 (2009), 012015/1-012015/15 ISSN 1742-6588. [International Conference On Superconductivity and Magnetism (ICSM2008). Side-Antalya, 25.08.2008–29.08.2008] R&D Projects: GA ČR GA202/08/0722 Institutional research plan: CEZ:AV0Z10100520 Keywords : (Nd,Eu,Gd)Ba 2 Cu 3 O y * annealing effect * pinning * critical currents Subject RIV: BM - Solid Matter Physics ; Magnetism

  2. Noise measurements of YBa2Cu3O7 thin film high-temperature superconductors

    International Nuclear Information System (INIS)

    Hall, J.J.

    1992-01-01

    The characteristics of thin-film YBa2Cu3O7 superconductors were studied from the superconducting region through the transition region and into the normal region. The properties studied included the resistance-temperature, current-voltage, and electrical noise with concentration of measurements in the transition region. The resistance vs. temperature measurements show a zero resistance followed by a small rise in magnitude at the onset of resistance followed by a sharp increase until the resistance tapers off in the fully normal region. The a-axis films had a larger normal resistivity, a lower critical temperature, and a broader transition than the similar c-axis films. The current(I) - voltage(V) measurements were concentrated in the transition region. A power relation between I and V was found to be V varies as I a(T) where a(T) is temperature dependent starting high the onset of vortex formation, approaches 3 at the vortex unbinding temperature, and goes to 1 when fully normal. This behavior was predicted by the Kosterlitz-Thouless theory and was found experimentally in all four films measured. The current-induced electrical noise characteristics were measured for four samples varying in thickness and axis orientation. Each film exhibited a widely varying magnitude of the noise voltage spectral density (S V ) in the transition region with a leveling off when fully normal. The normalized noise (S V /V squared) showed a sharp decrease in magnitude from the onset of measurable noise continually decreasing until flattening out when fully normal. The a-axis films exhibited S V /V squared over 3 order of magnitude larger than the c-axis films in the transition and normal regions. The normalized temperature coefficient of resistance (beta) was plotted against S V /V squared on a log-log scale to see if the noise generated was due to temperature fluctuations (slope = 2)

  3. Formation of qualified BaHfO3 doped Y0.5Gd0.5Ba2Cu3O7-δ film on CeO2 buffered IBAD-MgO tape by self-seeding pulsed laser deposition

    Science.gov (United States)

    Liu, Linfei; Wang, Wei; Yao, Yanjie; Wu, Xiang; Lu, Saidan; Li, Yijie

    2018-05-01

    Improvement in the in-filed transport properties of REBa2Cu3O7-δ (RE = rare earth elements, REBCO) coated conductor is needed to meet the performance requirements for various practical applications, which can be accomplished by introducing artificial pinning centers (APCs), such as second phase dopant. However, with increasing dopant level the critical current density Jc at 77 K in zero applied magnetic field decreases. In this paper, in order to improve Jc we propose a seed layer technique. 5 mol% BaHfO3 (BHO) doped Y0.5Gd0.5Ba2Cu3O7-δ (YGBCO) epilayer with an inserted seed layer was grown on CeO2 buffered ion beam assisted deposition MgO (IBAD-MgO) tape by pulsed laser deposition. The effect of the conditions employed to prepare the seed layer, including tape moving speed and chemical composition, on the quality of 5 mol% BHO doped YGBCO epilayer was systematically investigated by X-ray diffraction (XRD) measurements and scanning electron microscopy (SEM) observations. It was found that all the samples with seed layer have higher Jc (77 K, self-field) than the 5 mol% BHO doped YGBCO film without seed layer. The seed layer could inhibit deterioration of the Jc at 77 K and self-filed. Especially, the self-seed layer (5 mol% BHO doped YGBCO seed layer) was more effective in improving the crystal quality, surface morphology and superconducting performance. At 4.2 K, the 5 mol% BHO doped YGBCO film with 4 nm thick self-seed layer had a very high flux pinning force density Fp of 860 GN/m3 for B//c under a 9 T field, and more importantly, the peak of the Fp curve was not observed.

  4. Luminescence and energy transfer of Tb3+-doped BaO-Gd2O3-Al2O3-B2O3-SiO2 glasses.

    Science.gov (United States)

    Zuo, Chenggang; Huang, Jinze; Liu, Shaoyou; Xiao, Anguo; Shen, Youming; Zhang, Xiangyang; Zhou, Zhihua; Zhu, Ligang

    2017-12-05

    Transparent Tb 3+ -doped BaO-Gd 2 O 3 -Al 2 O 3 -B 2 O 3 -SiO 2 glasses with the greater than 4g/cm 3 were prepared by high temperature melting method and its luminescent properties have been investigated by measured UV-vis transmission, excitation, emission and luminescence decay spectra. The transmission spectrum shows there are three weak absorption bands locate at about 312, 378 and 484nm in the glasses and it has good transmittance in the visible spectrum region. Intense green emission can be observed under UV excitation. The effective energy transfer from Gd 3+ ion to Tb 3+ ion could occur and sensitize the luminescence of Tb 3+ ion. The green emission intensity of Tb 3+ ion could change with the increasing SiO 2 /B 2 O 3 ratio in the borosilicate glass matrix. With the increasing concentration of Tb 3+ ion, 5 D 4 → 7 F J transitions could be enhanced through the cross relaxation between the two nearby Tb 3+ ions. Luminescence decay time of 2.12ms from 546nm emission is obtained. The results indicate that Tb 3+ -doped BaO-Gd 2 O 3 -Al 2 O 3 -B 2 O 3 -SiO 2 glasses would be potential scintillating material for applications in X-ray imaging. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Structural evolution and electrical properties of BaTiO{sub 3} doped with Gd{sup 3+}

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez Lara, Juan Pablo; Perez Labra, Miguel; Barrientos Hernandez, Francisco Raul, E-mail: miguelabra@hotmail.com [Autonomous University of Hidalgo (Mexico); Romero Serrano, Jose Antonio; Hernandez Ramirez, Aurelio [Metallurgy and Materials Department, ESIQIE-IPN, UPALM, Zacatenco (Mexico); Avila Davila, Erika Osiris [Mechanical Engineering Department, Technological Institute of Pachuca, Hidalgo (Mexico); Thangarasu, Pandiyan [Facultad de Quimica, UNAM, Mexico D.F. (Mexico)

    2017-03-15

    BaTiO{sub 3} doped with Gd{sup 3+} (Ba{sub 1-x}Gd{sub x}Ti{sub 1-x/4}O{sub 3}) was synthesized using the solid-state reaction method with x = 0.001, 0.003, 0.005, 0.01, 0.05, 0.1, 0.15, 0.20, 0.25, 0.30, and 0.35 Gd{sup 3+} (wt. %). The powders were decarbonated at 900 °C and sintered at 1400 °C for 8 hours. The tetragonality of the synthesized Gd{sup 3+}-doped BaTiO{sub 3} particles was analyzed. XRD patterns and Raman spectra revealed that the crystal phase of the obtained particles was predominately tetragonal BaTiO{sub 3}; the intensity of the Raman bands at 205 cm{sup -1}, 265 cm{sup -1}, and 304 cm{sup -1} decreased when Gd'3{sup +} was increased. A secondary phase (Gd{sub 2}Ti{sub 2}O{sub 7}) was found when the Gd{sup 3+} content was higher than 0.15 wt. %. The capacitance of the sintering pellets was measured at 1 kHz; these values were used to calculate the relative permittivity, the maximum permittivity values were recorded for the samples with x = 0.001, 0.005, and 0.1. (author)

  6. Isomers of (Ca0.1La0.9)(Ba1.65La0.35)Cu3Oy Superconductor Having Different Tc

    International Nuclear Information System (INIS)

    Knizhnik, A.; Reisner, G.M.; Men, A.; Eckstein, Y.

    1998-01-01

    (Ca 0.1 La 0.9 )(Ba 1.65 La 0.35 )Cu 3 O y is a YBCO like superconductor but tetragonal for any y, i.e. without ordered chains. Its T c vs y plot has no intermediate plateau and is a nearly straight line in the under doped region. Different oxygen contents were obtained by oxygenation at various temperatures under 1 atm O 2 followed by quench in liquid nitrogen. This type of oxygenation leads to samples where the oxygen content corresponds to the thermodynamic equilibrium with the gas phase because the form of attaining the oxygenation temperature (Tom higher or lower temperature) and time (over 10h) of oxygenation do not change y and Tc. Changing of the firing temperature (we used the usual carbonate-oxide preparation which included 3 firings in powder, pelletization, sintering and oxygenation) changes Tc at the same y. The increase of the firing temperature by 40 deg C increases T c by 7-10K while y remains unchanged. Increases of the temperature of sintering virtually do not change T c which shows that low and high Tc compounds are formed during the first stages of preparation and that there is no thermodynamic equilibrium between them. The low Tc compounds cannot be transformed into high Tc ones by raising the temperature

  7. Processing of bulk Bi-2223 high-temperature superconductor

    Directory of Open Access Journals (Sweden)

    Alexander Polasek

    2005-12-01

    Full Text Available The Bi2Sr2Ca2Cu3 O10+x (Bi-2223 is one of the main high temperature superconductors for applications. One of these applications is the Superconductor Fault Current Limiter (SCFCL, which is a very promising high temperature superconducting device. SCFCL's can be improved by using bulk superconductors with high critical currents, which requires a sufficiently dense and textured material. In the present work, a process for improving the microstructure of Bi-2223 bulk samples is investigated. Pressed precursor blocks are processed by sintering with a further partial melting step, in order to enhance the Bi-2223 grain texture and to healing cracks induced by pressing. In order to improve the microstructure, the precursor is mixed with silver powder before pressing. Samples with and without silver powder have been studied, with the aim of investigating the influence of silver on the microstructure evolution. The phase contents and the microstructure obtained have been analyzed through XRD and SEM/EDS. The electromagnetic characterization has been performed by Magnetic Susceptibility Analysis. We present and discuss the process and the properties of the superconducting blocks. High fractions of textured Bi-2223 grains have been obtained.

  8. High-Q Tl2CaBa2Cu2O8 high-Tc superconducting quasi-optical millimeter-wave bandpass filters working at 77 K

    International Nuclear Information System (INIS)

    Zhang, D.; Fetterman, H.R.

    1994-01-01

    Tl 2 CaBa 2 Cu 2 O 8 high-temperature superconducting thin films with T c 's of over 100 K on LaAlO 3 substrates were used to fabricate quasi-optical millimeter-wave bandpass filters. Q-factors of over 400 were achieved, at liquid nitrogen temperatures from these filters at W-band frequencies (75--110 GHz)

  9. 17O knight shifts of the various types of CuO2 planes in Bi-cuprates high-Tc superconductors

    International Nuclear Information System (INIS)

    Le Noc, L.; Trokiner, A.; Schneck, J.; Pougnet, A.M.; Mellet, R.; Primot, J.; Savary, H.

    1992-01-01

    A 17 O NMR study has been performed on a 17 O enriched powder sample of (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O y , also called n=3 phase (with Tc=110K) which belongs to the Bi-based superconductors family (Bi,Pb) 2 Sr 2 Ca n-1 Cu n O 2n+4 . The n=3 compound which contains in its unit cell two types of CuO 2 planes (labelled type I and II), is compared to the n=2 compound where only one type of CuO 2 planes (type I) is present. 17 O Knight shift measurements versus temperature, in the normal phase, have allowed us to evidence the distinct behaviours of the two types of planes present in the n=3 compound. The results are consistent with the existence of stronger electron correlations, or smaller charge carrier density in the type II planes. 14 refs., 3 figs

  10. X-ray fluorescence determination of composition of the high temperature superconductors by the fundamental parameter method

    International Nuclear Information System (INIS)

    Mao Zhenwei; Shi Lei; Chen Shuyu; Zhou Guien

    2001-01-01

    Y, Pr, Ba and Cu compositions of the series of the Y 1-x Pr x Ba 2 Cu 3 O y samples have been determined by using X-ray fluorescence (XRF) fundamental parameter method in a non-destruction state. The composition is given by an atomic fraction. The determined compositions of the samples show a difference from their nominal compositions. One of the reasons why the exact shape of T c vs x varies is different from group to group, as reported, is the difference of the real and the nominal compositions. The relation of T c vs x is not a simple quadric curve. The results agree well with those obtained by the inductively coupled plasma atomic emission spectrometer (ICP-AES), which indicates that the method is appropriate for the determination of the compositions of the high temperature superconductors. In addition, the influence of oxygen on analytical elements is discussed. The fraction of the matrix total mass absorption, which is associated with oxygen for each analytical line, is less than 3.41%

  11. Doping effects in high-T{sub c} superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Hessel Andersen, N.

    1996-11-01

    The purpose of the project has been to study how the superconducting and magnetic properties of the high temperature superconductors change as function of oxygen stoichiometry and cation doping. The primary system of investigation has been YBa{sub 2}Cu{sub 3}O{sub 6+x}, which has been studied as function of oxygen stoichiometry, 0 < x < 1, and cation doping with Al, Co and Fe on the Cu-sites and Nd and Pr on the Y-site. In these materials the hole doping into the CuO{sub 2} planes, that is necessary for superconductivity, is strongly depending on structural ordering. The static properties and the kinetics of the structural ordering process have been studied experimentally by neutron and high energy synchrotron x-ray diffraction, by Raman scattering, and by computer simulation technique. Not only the oxygen stoichiometry but also the cation doping has been shown to influence the magnetic phases, in some cases in an unexpected manner. Thus, by neutron diffraction experiments it has been shown that doping with non-magnetic Al gives rise to a new magnetic phase. A theoretical model, has been developed. The magnetic phases of the Cu and Nd ordering in NdBa{sub 2}Cu{sub 3}O{sub 6+x}, and of the Cu and Pr ordering in PrBa{sub 2}Cu{sub 3}O{sub 6+x} have been studied by neutron diffraction with the main purpose of understanding why PrBa{sub 2}Cu{sub 3}O{sub 6+x} is magnetic and non-superconducting for all oxygen stoichiometries. In NdBa:2Cu{sub 3}O{sub 6+x} studies of the magnetic flux lattice have been carried out by Small Angle Neutron Scattering. Additional structural studies of the superconducting and magnetic phases of related materials, of RENi{sub 2}B{sub 2}C (RE = rare earth), and of oxidized and cation doped materials based on La{sub 2}CuO{sub 4+{delta}} have been carried out. Methods for structural studies and analyses, and equipment for electrical and magnetic characterization have been developed. (EG) 5 tabs., 46 ills., 35 refs.

  12. Hall effect and magnetization in the magnetic superconductor RuSr2GdCu2O8

    International Nuclear Information System (INIS)

    Jurelo, A.R.; Pimentel, J.L.; Wolff Fabris, F.; Schaf, J.; Pureur, P.; Vieira, V.N.

    2006-01-01

    We report on Hall effect, longitudinal resistivity and magnetization measurements in the rutheno-cuprate RuSr 2 GdCu 2 O 8 . Combining these results we separate the anomalous contribution to the Hall effect and argue that the occurrence of canting and chirality have to be considered for describing this property

  13. High current density in bulk YBa2Cu3O/sub x/ superconductor

    International Nuclear Information System (INIS)

    Salama, K.; Selvamanickam, V.; Gao, L.; Sun, K.

    1989-01-01

    A liquid phase processing method for the fabrication of bulk YBa 2 Cu 3 O/sub x/ superconductors with large current carrying capacity has been developed. Slow cooling through the peritectic transformation (1030--980 degree C) has been shown to control the microstructure of these superconductors. A cooling rate of 1 degree C/h in this temperature range has yielded a microstructure with long plate type, thick grains oriented over a wide area. Current density up to 18 500 A/cm 2 has been obtained by continuous direct current measurements and in excess of 62 000 A/cm 2 with pulse current of 10 ms duration and 75 000 A/cm 2 using 1 ms pulse. The strong magnetic field dependence observed in sintered bulk 1-2-3 superconductors is also minimized to a large extent where a current density in excess of 37 000 A/cm 2 is obtained in a field of 6000 G

  14. Fabrication and characterization of LRE.sub.1+x./sub.Ba.sub.2-x./sub.Cu.sub.3./sub.O.sub.y./sub. (LRE:Nd, Eu, Gd,NEG) superconductors:a low oxygen partial pressure

    Czech Academy of Sciences Publication Activity Database

    Muralidhar, M.; Sakai, N.; Jirsa, Miloš; Murakami, M.

    378-381, - (2002), s. 646-650 ISSN 0921-4534. [International Symposium on Superconductors /14./. Kobe, 25.09.2001-27.09.2001] R&D Projects: GA AV ČR IAA1010919 Institutional research plan: CEZ:AV0Z1010914 Keywords : melt processing * microstructure * critical current density (J c ) * flux pinning * LRE-Ba2Cu3Oy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.912, year: 2002

  15. Studies at IBM on anisotropy in single crystals of the high-temperature oxide superconductor Y1Ba2Cu3O7/sub -//sub x/ (invited)

    International Nuclear Information System (INIS)

    Gallagher, W.J.

    1988-01-01

    A series of studies carried out at IBM on the magnetic, transport, and optical properties of single crystal Y 1 Ba 2 Cu 3 O/sub 7-//sub x/ demonstrate the overriding importance of anisotropy in its superconducting and normal-state properties

  16. Electron mass anisotropy of BaZrO3 doped YBCO thin films in pulsed magnetic fields up to 30 T

    International Nuclear Information System (INIS)

    Palonen, H; Huhtinen, H; Paturi, P; Shakhov, M A

    2013-01-01

    The high anisotropy of the critical current density in the high-temperature superconductor YBa 2 Cu 3 O 6+x can be compensated by changing the pinning landscape, for example, through doping with BaZrO 3 . We measure the change due to BaZrO 3 doping in the effective electron mass anisotropy, γ, by resistive measurements of the upper critical field in pulsed high magnetic fields. It is found that the angular dependence of the upper critical field follows the Blatter scaling up to 30 T but the irreversibility field does not. We also report a significant reduction in the effective electron mass anisotropy from 6.0 to 3.4 by BaZrO 3 doping. (paper)

  17. High pressure {mu}SR studies: rare earths and related materials

    Energy Technology Data Exchange (ETDEWEB)

    Kalvius, G.M., E-mail: kalvius@ph.tum.de; Schreier, E. [Technical University Munich, Physics Department (Germany)], E-mail: kalvius@ph.tum.de; Ekstroem, M.; Hartmann, O. [Uppsala University, Physics Department (Sweden); Henneberger, S., E-mail: kalvius@ph.tum.de; Kratzer, A. [Technical University Munich, Physics Department (Germany)], E-mail: kalvius@ph.tum.de; Waeppling, R. [Uppsala University, Physics Department (Sweden); Martin, E., E-mail: kalvius@ph.tum.de; Burghart, F.J. [Technical University Munich, Physics Department (Germany)], E-mail: kalvius@ph.tum.de; Ballou, R.; Deportes, J. [CNRS, Laboratoire Louis Neel (France); Niedermayer, Ch. [University of Constance, Faculty of Physics (Germany)

    2000-11-15

    After a short introduction to {mu}SR with respect to the study of magnetic properties, followed by a brief outline of the principle of the high pressure-low temperature {mu}SR spectrometer installed at the Paul Scherrer Institute, we discuss some measurements on rare earth materials employing this instrument. They are concerned with: (1) The pressure dependence of the spin turning process in ferromagnetic Gd. (2) The volume dependence of the internal magnetic field in the heavy rare earth metals Gd, Dy, and Ho in their ordered magnetic states. (3) The response of the (first order) magnetic transition in the frustrated antiferromagnets of type RMn{sub 2} (R = Y,Gd) to pressure. (4) The variation of magnetic parameters with pressure in La{sub 2}CuO{sub 4} (powder sample), the antiferromagnetic parent compound of the high T{sub C} superconductors of type La{sub 2-x}(Sr, Ba){sub x}CuO{sub 4}. In conclusion a short outlook on further developments is given.

  18. Flux-line cutting in granular high-temperature superconductors

    International Nuclear Information System (INIS)

    Perez-Rodriguez, F.; Perez-Gonzalez, A.; Clem, J.R.; Gandolfini, G.; LeBlanc, M.A.

    1997-01-01

    The magnetic response of granular high-temperature superconducting plates subjected to a dc-bias magnetic field and an increasing field perpendicular to it is studied both experimentally and theoretically. The theoretical model is based upon the double critical-state model, which considers not only flux transport but also flux-line cutting effects. Curves of magnetization for the system of grains decoupled by the applied magnetic field in sintered slabs of YBa 2 Cu 3 O 7-x and NdBa 2 Cu 3 O 7-x are analyzed. Good agreement between experimental results and theory is obtained. copyright 1997 The American Physical Society

  19. Practical superconductor development for electrical power applications

    International Nuclear Information System (INIS)

    Goretta, K.C.

    1991-10-01

    Development of useful high-critical-temperature (high-T c ) superconductors requires synthesis of superconducting compounds; fabrication of wires, tapes, and films from these compounds; production of composite structures that incorporate stabilizers or insulators; and design and testing of efficient components. This report describes technical progress of research and development efforts aimed at producing superconducting components based on the Y-Ba-Cu, Bi-Sr-Ca-Cu, Bi-Pb-Sr-Ca-Cu, and Tl-Ba-Ca-Cu oxides systems. Topics discussed are synthesis and heat treatment of high-T c superconductors, formation of monolithic and composite wires and tapes, superconductor/metal connectors, characterization of structures and superconducting and mechanical properties, and fabrication and properties of thin films. Collaborations with industry and academia are also documented. 10 figs

  20. The evidence of unconventional pairing in heavy fermion superconductors and high-Tc superconductors

    International Nuclear Information System (INIS)

    Tien, C.; Wur, C.S.; Jiang, I.M.

    1989-01-01

    Recently there has been a great deal of interest in two classes of superconductors, heavy fermion superconductors and high T c copper oxide superconductors. The behavior and nature of superconductivity in these two classes of materials are very similar. The temperature dependences of spin-lattice relaxation time (T 1 ) and spin-spin relaxation time (T 2 ) of 9 Be in UBe 13 are quite similar to those of 63 Cu and 89 Y in YBa 2 Cu 3 O 7-δ . The Knight shift of UBe 13 is unchanged during the superconducting phase transition. The Knight shift of YBa 2 Cu 3 O 7-δ changes from the value in the normal state K n /K s = 1 at T ≥ T c to K n /K s = 0.5 at T = 6 K. Both do not approach zero as expected in BCS theory. The acoustic attenuation is enhanced just below T c instead of rapid drop near T c for these two superconducting system. Neither the enhancement, the temperature variation, nor any other anomalous behaviors appear to be mirrored in EPR data for heavy Fermion superconductors and high T c superconductors. This strongly suggests that the unconventional pairing mechanism which induces superconductivity in heavy fermion materials might also involve in high T c superconductors

  1. Critical current properties in superconducting melt processed Y-Ba-Cu-O

    International Nuclear Information System (INIS)

    Matsushita, Teruo

    1993-01-01

    The critical current density in bulk superconducting Y-Ba-Cu-O has been remarkably improved by employing the so-called melt process. However, its value is still far below those reported in single-crystalline thin films. Important key factors that determine the critical current density are the flux pinning mechanism and defective structures such as cracks or weak links. In this article, these factors in melt-processed Y-Ba-Cu-O are argued from various measurements of the critical current density on the microstructure dependence, the magnetic field dependence, the temperature dependence, the history effect, the longitudinal field effect and the imaginary ac susceptibility. As for the pinning mechanism, it is concluded that the dominant pinning centers in the high temperature region around 77 K are normal 211 (Y 2 BaCuO 5 ) particles, while small defects such as lattice defects or oxygen deficiencies seem to be dominant in the lower temperature region. It is suggested that much finer normal particles should be introduced in order to improve the critical current density especially at higher temperatures. From the rapid decrease of the critical current density with elevating temperature below 30 K, some kind of weak links are considered to still remain in these materials. However, the observed critical current density did not depend on the history of application of the magnetic field and a large enhancement of the critical current density was observed in the longitudinal field geometry at 4.2 K. These results suggest that the weak links in these materials are of much different kind from those at large angle grain boundaries in sintered polycrystalline materials. From the X-ray diffraction measurements, a domain structure of a mean domain size of about 100 μm was found. These domain boundaries may cause weak links in melt-processed Y-Ba-Cu-O. It is also shown that the typical size of channels of flowing current can be obtained by the imaginary ac susceptibility

  2. Multiphase nanodomains in a strained BaTiO3 film on a GdScO3 substrate

    Science.gov (United States)

    Kobayashi, Shunsuke; Inoue, Kazutoshi; Kato, Takeharu; Ikuhara, Yuichi; Yamamoto, Takahisa

    2018-02-01

    Controlling the crystal structure of ferroelectric materials via epitaxial strain, which is a well-known technique in strain engineering, can lead to the formation of unique domain structures generating non-intrinsic phenomena such as electronic conductivity, photovoltages, and enhanced piezoelectric characteristics. Strained BaTiO3 films are promising ferroelectric materials as theoretical modeling predicts that different domain morphologies can introduce additional properties not observed in conventional BaTiO3 ceramics. To rationally design materials for practical application, a thorough understanding of the formation mechanisms and stabilities of different domain structures in strained BaTiO3 films is required. However, there have been very few experimental reports on this topic, and details about the domain structures in strained BaTiO3 films are currently lacking. In this paper, we report multiphase nanodomains in a strained BaTiO3 film deposited on an orthorhombic GdScO3 substrate. The phase-transition behavior of the strained BaTiO3 film reveals that it contains multiple phases at room temperature; the film first undergoes a phase-transition upon heating at around 550 K, and then a paraelectric phase forms at temperatures above 690 K. A picometer-scale analysis of the Ti ion displacements, using an advanced scanning transmission electron microscopy technique, is used to characterize the complex multiphase nanodomains, providing useful insights into the control of domain structures in BaTiO3 films by applying epitaxial strain.

  3. Method of fabricating a (1223) Tl-Ba-Ca-Cu-O superconductor

    Science.gov (United States)

    Tkaczyk, J.E.; Lay, K.W.; He, Q.

    1997-07-08

    A method is disclosed for fabricating a polycrystalline thallium-containing superconductor having high critical current at elevated temperatures and in the presence of a magnetic field. A powder precursor containing compounds other than thallium is compressed on a substrate. Thallium is incorporated in the densified powder precursor at a high temperature in the presence of a partial pressure of a thallium-containing vapor. 2 figs.

  4. Harmonic and static susceptibilities of YBa2Cu3O7

    International Nuclear Information System (INIS)

    Ishida, T.; Goldfarb, R.B.; Okayasu, S.; Kazumata, Y.; Franz, J.; Arndt, T.; Schauer, W.

    1993-01-01

    Intergranular properties of the sintered superconductor YBa 2 Cu 3 O 7 have been studied in terms of complex harmonic magnetic susceptibility χ n χ n ' - iχ n '' (n integer) as well as DC susceptibility χ dc . As functions of temperature T, χ 1 ' and χ 1 '' depend on both the AC magnetic-field amplitude H ac and the magnitude of a superimposed DC field H dc . Only odd-harmonic susceptibilities are observed below the critical temperature, T c , for zero H dc while both odd and even harmonics are observed for nonzero H dc . With T constant, odd-harmonic susceptibilities are even functions of H dc , whereas even-harmonic susceptibilities are odd functions of H dc . Experimental intergranular characteristics of χ n ' and χ n '' are in good agreement with theoretical predictions from a simplified Kim model of magnetization. In contrast, even-harmonic susceptibilities measured for a GdBa 2 Cu 3 O 7 thin film and an YBa 2 Cu 3 O 7 single crystal are not prominent due to missing weak links, whereas odd-harmonic susceptibilities are remarkable. A survey of several models for the harmonic response of superconductors is presented. The DC susceptibility curve for the zero-field-cooled YBa 2 Cu 3 O 7 sample, χ ZFC (T), has a two-step structure arising from intra- and inter-granular components, similar to χ 1 '. DC susceptibility measured upon warming, χ FCW (T), shows a negative peak near T c for the sample cooled rapidly in small DC fields. DC susceptibility measured upon cooling, χ FCC (T), does not show a peak. A negative peak is not seen in measurements on a powdered sample. The negative peak can be explained by intergranular flux depinning upon warming. (orig.)

  5. Over 15 MA/cm2 of critical current density in 4.8 µm thick, Zr-doped (Gd,Y)Ba2Cu3Ox superconductor at 30 K, 3T.

    Science.gov (United States)

    Majkic, Goran; Pratap, Rudra; Xu, Aixia; Galstyan, Eduard; Selvamanickam, Venkat

    2018-05-03

    An Advanced MOCVD (A-MOCVD) reactor was used to deposit 4.8 µm thick (Gd,Y)BaCuO tapes with 15 mol% Zr addition in a single pass. A record-high critical current density (J c ) of 15.11 MA/cm 2 has been measured over a bridge at 30 K, 3T, corresponding to an equivalent (I c ) value of 8705 A/12 mm width. This corresponds to a lift factor in critical current of ~11 which is the highest ever reported to the best of author's knowledge. The measured critical current densities at 3T (B||c) and 30, 40 and 50 K, respectively, are 15.11, 9.70 and 6.26 MA/cm 2 , corresponding to equivalent Ic values of 8705, 5586 and 3606 A/12 mm and engineering current densities (J e ) of 7068, 4535 and 2928 A/mm 2 . The engineering current density (J e ) at 40 K, 3T is 7 times higher than that of the commercial HTS tapes available with 7.5 mol% Zr addition. Such record-high performance in thick films (>1 µm) is a clear demonstration that growing thick REBCO films with high critical current density (J c ) is possible, contrary to the usual findings of strong J c degradation with film thickness. This achievement was possible due to a combination of strong temperature control and uniform laminar flow achieved in the A-MOCVD system, coupled with optimization of BaZrO 3 nanorod growth parameters.

  6. Anomalous properties of PrBa2Cu3O7: a comment

    International Nuclear Information System (INIS)

    Sampathkumaran, E.V.

    1992-01-01

    Considerable attention has been paid in the literature to understand the suppression of superconductivity and the large Neel temperature of the Pr sub-lattice in PrBa 2 Cu 3 O 7 . Here we briefly recall the superconducting and magnetic anomalies noted earlier in other Pr based systems due to the partial delocalisation of the Pr-4f orbital to show that the gross anomalous features observed for PrBa 2 Cu 4 O 7 are not unique. (orig.)

  7. Critical current density above 15 MA cm−2 at 30 K, 3 T in 2.2 μm thick heavily-doped (Gd,Y)Ba2Cu3Ox superconductor tapes

    International Nuclear Information System (INIS)

    Selvamanickam, V; Gharahcheshmeh, M Heydari; Xu, A; Zhang, Y; Galstyan, E

    2015-01-01

    A critical current (I c ) value of 3963 A/12 mm, corresponding to a critical current density (J c ) of 15 MA cm −2 has been achieved at 30 K, 3 T in the orientation of field parallel to the c-axis (B||c) in 2.2 μm thick film (Gd,Y)BaCuO tapes with 20 mol% Zr addition made by metal organic chemical vapor deposition. This J c level is more than a factor of four higher than the J c values of 7.5 mol% Zr-added tapes, which are an industry benchmark. The critical current values in a magnetic field of 3 T parallel to the c-axis in the 2.2 μm thick, 20 mol% Zr-added tape reached 2833 A/12 mm (10.1 MA cm −2 ), 1881 A/12 mm (7.1 MA cm −2 ) and 805 A/12 mm (3.1 MA cm −2 ) at 40 K, 50 K and 65 K respectively. Such high critical current values were possible because of maintaining a strong alignment of BaZrO 3 nanocolumns along the c-axis over the entire film thickness. (fast track communication)

  8. Effect of rare-earth composition on microstructure and pinning properties of Zr-doped (Gd, Y)Ba{sub 2}Cu{sub 3}O{subx} superconducting tapes.

    Energy Technology Data Exchange (ETDEWEB)

    Selvamanickam, V.; Chen, Y.; Zhang, Y.; Guevara, A.; Shi, T.; Yao, Y.; Majkic, G.; Lei, C.; Galtsyan, E.; Miller, D. J. (Materials Science Division); (Univ. Houston); (SuperPower Inc.)

    2012-01-01

    The effect of changing Gd + Y content from 1.2 to 1.6 in the precursor of (Gd,Y)Ba{sub 2}Cu{sub 3}O{sub 7} superconducting thin film tapes made by metal organic chemical vapor deposition (MOCVD) at a constant Gd:Y ratio and a fixed Zr content of 7.5% has been studied. The influence of changing the Gd:Y ratio from Gd = 0 to Y= 0 in 0.2 mol steps at a constant Gd + Y content of 1.2 in the precursor has also been investigated at a fixed Zr content of 7.5%. The critical current of these films is found to vary significantly as a function of rare-earth content as well as a function of rare-earth type. Even for a fixed Zr content, it is found that the critical current in the orientation of magnetic field parallel to the a-b plane and that in the orientation of field perpendicular to the a-b plane can be systematically varied with changing Gd + Y content as well as with changing Gd:Y ratio. The nanoscale defect structures along the a-b plane and along the c-axis are found to be sensitive to these changes in rare-earth content and type.

  9. ESR in the Y[sub 1-x]Gd[sub x]Ba[sub 2]Cu[sub 3]O[sub 7] system below T[sub c

    Energy Technology Data Exchange (ETDEWEB)

    Deville, A. (Electronique des Milieux Condenses, Univ. de Provence, 13 Marseille (France)); Bejjit, L. (Electronique des Milieux Condenses, Univ. de Provence, 13 Marseille (France)); Gaillard, B. (Electronique des Milieux Condenses, Univ. de Provence, 13 Marseille (France)); Noel, H. (Chimie du Solide et Inorganique Moleculaire, Univ. de Rennes, 35 Rennes (France)); Potel, M. (Chimie du Solide et Inorganique Moleculaire, Univ. de Rennes, 35 Rennes (France)); Monnereau, O. (Chimie des Materiaux, Univ. de Provence, 13 Marseille (France))

    1994-02-01

    The ESR spectra from GdBa[sub 2]Cu[sub 3]O[sub 7] between 300 and 10 K are presented and shortly discussed. Below Tc, the signal from sintered samples is lost (X band) or weak (Q band). The ESR line from single crystals, while Dysonian and isotropic at 300 K, is symmetrical and significantly anisotropic below 40 K, and presents then an additional narrowing when H // ab. In the dilute compounds (x < or [approx] .02) an experimental answer is given to a question raised at LT19, to be solved before low T studies. (orig.)

  10. Supercurrent transport properties in Nd substituted TlSr2CaCu2O7 high temperature superconductor

    International Nuclear Information System (INIS)

    Andrew Das Arulsamy; Abd Shukor, R.

    1999-01-01

    The transport critical current density, J ct of TI(Sr 1-x Nd x ) 2 CaCu 2 O 7 (x= 0.1, 0.2 and 0.3) high temperature superconductors were measured at various temperatures. X-ray diffraction patterns indicate that all samples consist of mainly of the 1212 phase. The variation of J ct with Nd concentration, temperature and T c were scaled using a universal function. By plotting J ct versus T n c (x) and [1-(T/T c ) 2 ] m , we can divide the temperature dependencies of J ct into two regions. In each region, a linear relationship is suggested to hold between J ct and [1-(T/T c ) 2 ] m . For x=0.1, a relatively large exponent m in the range 40 - 50 K is observed, but a lower value is observed for a higher temperature range, 55 - 60 K. Average m for x = 0. 1 in the range 40 - 70 K is 1.8 but for x=0.2 and 0.3, m is 0.6 and 1.2, respectively. This can be interpreted as an indication that there is a change in the elementary flux pinning force which is responsible for sustaining the supercurrent. A self-field approximation indicates that Nd substitution lowers the distance between pinning centers (L c ). (author)

  11. Experimental study of the plasma fluorination of Y-Ba-Cu-O thin films

    CERN Document Server

    Li Qi; Ji Zheng Ming; Feng Yi Jun; Kang Lin; Yang Sen Zu; Wu Pei Heng; Wang Xiao Shu; Ye Yuda

    2002-01-01

    The authors have experimentally studied the surface modifications of Y-Ba-Cu-O (YBCO) thin films using CF sub 4 plasma. The intensity of the plasma fluorination was controlled by changing the biasing voltage and the time of the plasma treatment. Microstructural analyses reveal that the oxygen content of the YBCO thin films was changed. Transport measurements of sufficient fluorinated YBCO films imply that the films changed totally into an oxygen-deficient semi-conducting state. From these experimental results, the authors believe that plasma fluorination is quite a useful method to form controllable a thin barrier layer in fabricating interface engineered junctions and to form a stable narrow weak-link region in fabricating planar superconductor-normal-superconductor junctions

  12. Effect of rare-earth ion size on local electron structure in RBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (R = Tm, Dy, Gd, Eu, Nd and Y) superconductors: A positron study

    Energy Technology Data Exchange (ETDEWEB)

    Chen Zhenping [Department of Technology and Physics, Zhengzhou University of Light Industry, 5 Dongfeng Road, Zhengzhou, Henan 450002 (China)]. E-mail: czhping@zzuli.edu.cn; Zhang Jincang [Department of Physics, Shanghai University, Shanghai 200436 (China); Su Yuling [Department of Technology and Physics, Zhengzhou University of Light Industry, 5 Dongfeng Road, Zhengzhou, Henan 450002 (China); Xue Yuncai [Department of Technology and Physics, Zhengzhou University of Light Industry, 5 Dongfeng Road, Zhengzhou, Henan 450002 (China); Cao Shixun [Department of Physics, Shanghai University, Shanghai 200436 (China)

    2006-02-15

    The effects of rare-earth ionic size on the local electron structure, lattice parameters and superconductivity have been investigated by positron annihilation technique (PAT) and related experiments for RBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (R = Tm, Dy, Gd, Eu, Nd and Y) superconductors. The local electron density n {sub e} is evaluated as a function of the rare-earth radius. The results show that both the bulk-lifetime {tau} {sub B} and the defect lifetime {tau} {sub 2} increase with increasing rare-earth ionic radius, while the local electron density n {sub e} decrease with increasing rare-earth ionic radius. These results prove that the changes of n {sub e}, the degree of orthorhombic distortion and the coupling between the Cu-O chains and the CuO{sub 2} planes all have an effect on the superconductivity of RBa{sub 2}Cu{sub 3}O{sub 7-{delta}} systems.

  13. Design of High Field Solenoids made of High Temperature Superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bartalesi, Antonio; /Pisa U.

    2010-12-01

    This thesis starts from the analytical mechanical analysis of a superconducting solenoid, loaded by self generated Lorentz forces. Also, a finite element model is proposed and verified with the analytical results. To study the anisotropic behavior of a coil made by layers of superconductor and insulation, a finite element meso-mechanic model is proposed and designed. The resulting material properties are then used in the main solenoid analysis. In parallel, design work is performed as well: an existing Insert Test Facility (ITF) is adapted and structurally verified to support a coil made of YBa{sub 2}Cu{sub 3}O{sub 7}, a High Temperature Superconductor (HTS). Finally, a technological winding process was proposed and the required tooling is designed.

  14. Y-Ba-Cu-O superconducting film on oxidized silicon

    International Nuclear Information System (INIS)

    Gupta, R.P.; Khokle, W.S.; Dubey, R.C.; Singhal, S.; Nagpal, K.C.; Rao, G.S.T.; Jain, J.D.

    1988-01-01

    We report thick superconducting films of Y-Ba-Cu-O on oxidized silicon substrates. The critical temperatures for onset and zero resistance are 96 and 77 K, respectively. X-ray diffraction analysis predicts 1, 2, 3 composition and orthorhombic phase of the film

  15. Ceramic high-temperature superconductors

    International Nuclear Information System (INIS)

    Marquart, R.

    1989-01-01

    The contribution presents an overview treatment of the structure of the new superconductors (YBa 2 Cu 3 O 7-x ). Methods of powder production and processing technology are described, with current development projects by Dornier being taken into consideration. (orig.) [de

  16. Cluster-assembled overlayers and high-temperature superconductors

    International Nuclear Information System (INIS)

    Ohno, T.R.; Yang, Y.; Kroll, G.H.; Krause, K.; Schmidt, L.D.; Weaver, J.H.; Kimachi, Y.; Hidaka, Y.; Pan, S.H.; de Lozanne, A.L.

    1991-01-01

    X-ray photoemission results for interfaces prepared by cluster assembly with nanometer-size clusters deposited on high-T c superconductors (HTS's) show a reduction in reactivity because atom interactions with the surface are replaced by cluster interactions. Results for conventional atom deposition show the formation of overlayer oxides that are related to oxygen depletion and disruption of the near-surface region of the HTS's. For cluster assembly of Cr and Cu, there is a very thin reacted region on single-crystal Bi 2 Sr 2 CaCu 2 O 8 . Reduced reactivity is observed for Cr cluster deposition on single-crystal YBa 2 Cu 3 O 7 -based interfaces. There is no evidence of chemical modification of the surface for Ge and Au cluster assembly on Bi 2 Sr 2 CaCu 2 O 8 (100). The overlayer grown by Au cluster assembly on Bi 2 Sr 2 CaCu 2 O 8 covers the surface at low temperature but roughening occurs upon warming to 300 K. Scanning-tunneling-microscopy results for the Au(cluster)/Bi 2 Sr 2 CaCu 2 O 8 system warmed to 300 K shows individual clusters that have coalesced into large clusters. These results offer insight into the role of surface energies and cluster interactions in determining the overlayer morphology. Transmission-electron-microscopy results for Cu cluster assembly on silica show isolated irregularly shaped clusters that do not interact at low coverage. Sintering and labyrinth formation is observed at intermediate coverage and, ultimately, a continuous film is achieved at high coverage. Silica surface wetting by Cu clusters demonstrates that dispersive force are important for these small clusters

  17. Critical current density in (YBa2Cu3O7-δ)1-x-(PrBa2Cu3O7-δ)x melt-textured composites

    Science.gov (United States)

    Opata, Yuri Aparecido; Monteiro, João Frederico Haas Leandro; Jurelo, Alcione Roberto; Siqueira, Ezequiel Costa

    2018-06-01

    Melt textured (YBa2Cu3O7-δ)1-x-(PrBa2Cu3O7-δ)x composites (x = 0.00 and x = 0.05) were grown using the top seeding method. The effect of the PrBa2Cu3O7-δ phase on the growth process and the modification of the microstructure as well as on the physical properties was analyzed. X-ray analyses indicated that both pure and Pr-doped samples present an orthorhombic superconducting phase. From resistivity measurements for YBa2Cu3O7-δ and (YBa2Cu3O7-δ)0.95-(PrBa2Cu3O7-δ)0.05 samples, the Tcab did not change and was around 90.5 K. However, from magnetic measurements, the superconductivity was observed in critical temperatures TC = 92.9 K and 92.4 K for YBa2Cu3O7-δ and (YBa2Cu3O7-δ)0.95-(PrBa2Cu3O7-δ)0.05 samples, respectively. The YBa2Cu3O7-δ sample showed higher critical current densities than those shown by the (YBa2Cu3O7-δ)0.95-(PrBa2Cu3O7-δ)0.05 sample, with values of JC = 5.85 × 105 A/cm2 and 4.72 × 105 A/cm2, respectively. This paper also discusses the importance of Pr substitution on nano- and micro-meter scales to enhance JC(H).

  18. Magnetic memory effects in high temperature superconductors

    International Nuclear Information System (INIS)

    Rockenbauer, A.

    1989-01-01

    Microwave absorption of high temperature oxide superconductors MBa 2 Cu 3 O 7 (M = Y, Er, Dy, Ho, Lu, Tm, Gd) at 77 K have been studied by ESR. In granular samples diamagnetic zero-field resonance and strong ESR baseline hysteresis have been observed: for increasing field sweep - a high, for decreasing one - a low, while in constant field the baseline approaches the middle position with kinetics typical of spin-glasses. The hysteresis amplitude, i.e. the deviation of high and low baselines, possesses maximum at zero field if the sample is cooled down in zero field. In case of field cooling both the diamagnetic resonance and hysteresis maximum are shifted as a function of relative direction of the fields where the samples are cooled and measured, respectively. The shift is caused by the remanent diamagnetism of trapped fluxons. The hysteresis critically depends on the modulation amplitude of magnetic field, and no hysteresis can be observed if the microwave absorption is detected without field modulation. By applying saw-tooth sweep the spin-glass can be driven between two extreme hysteresis states, and the ESR response is rectangular for large saw-tooth amplitude and linear - for small one, while for intermediate amplitudes the recording shows characteristic memory effects. The hysteresis memory is explained in terms of loop distribution of fluxons. In the single crystal the fluxon absorptions are also detected and the separation of fluxon lines can be related to the hysteresis in granular samples. (author)

  19. Microgravity Processing of Oxide Superconductors

    Science.gov (United States)

    Olive, James R.; Hofmeister, William H.; Bayuzick, Robert J.; Vlasse, Marcus

    1999-01-01

    Considerable effort has been concentrated on the synthesis and characterization of high T(sub c) oxide superconducting materials. The YBaCuO system has received the most intense study, as this material has shown promise for the application of both thin film and bulk materials. There are many problems with the application of bulk materials- weak links, poor connectivity, small coherence length, oxygen content and control, environmental reactivity, phase stability, incongruent melting behavior, grain boundary contamination, brittle mechanical behavior, and flux creep. The extent to which these problems are intrinsic or associated with processing is the subject of controversy. This study seeks to understand solidification processing of these materials, and to use this knowledge for alternative processing strategies, which, at the very least, will improve the understanding of bulk material properties and deficiencies. In general, the phase diagram studies of the YBaCuO system have concentrated on solid state reactions and on the Y2BaCuO(x) + liquid yields YBa2Cu3O(7-delta) peritectic reaction. Little information is available on the complete melting relations, undercooling, and solidification behavior of these materials. In addition, rare earth substitutions such as Nd and Gd affect the liquidus and phase relations. These materials have promising applications, but lack of information on the high temperature phase relations has hampered research. In general, the understanding of undercooling and solidification of high temperature oxide systems lags behind the science of these phenomena in metallic systems. Therefore, this research investigates the fundamental melting relations, undercooling, and solidification behavior of oxide superconductors with an emphasis on improving ground based synthesis of these materials.

  20. High temperature bismuth cuprate superconductors synthesis and characterization

    International Nuclear Information System (INIS)

    Mansori, M.; Satre, P.; Breandon, C.; Roubin, M.; Sebaoun, A.

    1993-01-01

    High temperature superconductor phases synthesis by coprecipitation in alkaline solution is reported. (Bi 1.6 Pb 0.4 )Sr 2 Ca 1 Cu 2 O 8+x and (Bi 1.6 Pb 0.4 )Sr 2 Ca 2 Cu 3 O 10+y noted (2212) and (2223) have been prepared and studied. From aqueous nitrate solutions of Bi, Pb, Sr, Ca and Cu and oxalic acid aqueous solution as well as ethylene glycol, using an organic base (the triethylamine), the pH was increased up to the path of the precipitation zone (pH = 10.5-11.2). This method assures a good granulometric homogeneity of powders. Thermal analysis and characterization of the different components produced during the synthesis have been studied by DTA (differential thermal analysis)- TGA (thermogravimetric analysis), X-ray diffraction at different temperatures and by Infrared spectroscopy with a Fourier transformation. The measurements of magnetic susceptibility for the 2212 (with and without lead) and 2223 (with lead) phases have permitted us to observe the critical temperatures of 84 K, 87 K and 114 K. (author). 29 refs., 2 figs., 4 tabs

  1. Neutron diffraction studies of high-T/sub c/ superconductors

    International Nuclear Information System (INIS)

    Jorgensen, J.D.

    1988-03-01

    Neutron powder diffraction techniques have been used extensively for the study of high-T/sub c/ oxide superconductors because of the need to locate oxygen atoms and accurately determine the oxygen site occupancies, and the difficulty in obtaining single crystals. For example, in the case of YBa 2 Cu 3 O/sub 7-δ/, neutron powder diffraction and Rietveld structural refinement were used to obtain the first complete structural information. Subsequent experiments focussed on determining the relationship of superconducting properties to the number and distribution of oxygen vacancies on the Cu-O sublattice with measurements being done on samples in thermodynamic equilibrium, at high temperature in controlled oxygen atmospheres, and on metastable, oxygen-deficient samples produced by quenching. Neutron powder diffraction has also been used to determine the structures of compounds in which the properties have been modified by substitution on the Y, Ba, or Cu sites. This paper briefly reviews some of the neutron powder diffraction results in these areas. 17 refs

  2. Current transport and electronic states in a,b-axis-oriented YBa2Cu3O7/PrBa2Cu3O7/YBa2Cu3O7 sandwich-type junctions

    International Nuclear Information System (INIS)

    Yoshida, J.; Nagano, T.; Hashimoto, T.

    1996-01-01

    Precise measurement of the temperature and voltage dependence of junction conductance has been carried out for a,b-axis-oriented YBa 2 Cu 3 O 7 /PrBa 2 Cu 3 O 7 /YBa 2 Cu 3 O 7 sandwich-type junctions to investigate the possible origin of Josephson coupling in these junctions. Regardless of the presence or absence of the Josephson effect, most of the junctions exhibited a dip in conductance around zero voltage in their dI/dV profiles at low temperatures. This dI/dV anomaly was attributed to the existence of a minimum in the density of states due to electron-electron interaction in disordered metals in the vicinity of a tunneling barrier within the junctions. The complex temperature dependence of junction conductance was reproduced well by a theoretical model in which both tunneling conduction paths and variable range hopping paths were assumed to exist within the PrBa 2 Cu 3 O 7 barrier layer. No definite evidence of current transport through a small number of localized levels or a metallic conduction path in PrBa 2 Cu 3 O 7 has been confirmed, even for junctions with a 20-nm-thick barrier layer. copyright 1996 The American Physical Society

  3. Preparation of high-temperature superconducting ceramics

    International Nuclear Information System (INIS)

    Causa, M.T.; Dutrus, S.M.; Esparza, Daniel; Fainstein, Carlos; Malachevsky, M.T.; Salva, Horacio; Sanchez, Rodolfo; Steren, L.B.; Tovar, Manuel; Veglio, Nestor

    1987-01-01

    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) [es

  4. Raman study of HgBa 2Ca n-1 Cu nO 2 n+2+ δ ( n=1,2,3,4 and 5) superconductors

    Science.gov (United States)

    Zhou, Xingjiang; Cardona, M.; Chu, C. W.; Lin, Q. M.; Loureiro, S. M.; Marezio, M.

    1996-02-01

    Polarized micro-Raman scattering measurements have been performed on the five members of the HgBa 2Ca n-1 Cu nO 2 n+2+ δ ( n=1,2,3,4 and 5) high- Tc superconductor family using different laser frequencies. Local laser annealing measurements were carried out to investigate the variation of the Raman spectra with the excess oxygen content, δ. A systematic evolution of the spectra, which display mainly peaks near 590, 570, 540 and 470 cm -1, with increasing number of CuO 2 layers has been observed; its origin has been shown to lie in the variation of the interstitial oxygen content. In addition to confirming that the 590 cm -1 mode represents vibration of apical oxygens in the absence of neighboring excess oxygen, the 570 cm -1 mode, which may be composed of some finer structures, has been assigned to the vibration of the apical oxygen modified by the presence of the neighboring excess oxygens. The 540 and 470 cm -1 modes may represent the direct vibration of excess oxygens. The implication of possible different distribution sites of excess oxygens is discussed. All other observed lower-frequency modes are also assigned.

  5. Comparative analysis of the physical properties of Y-Ba-Cu-O when substituting Ce and Nd in place of Y

    International Nuclear Information System (INIS)

    Lee, Jong Rok; Jhung, Byung Doo; Woo, Chang Woong

    1996-01-01

    The physical properties of the superconductors Y 1-x Ce x Ba 2 Cu 3 O 7-y and Y 1-x Nd x Ba 2 Cu 3 O 7-y made by the solid-state reaction method were carefully examined after substituting Ce and Nd (x=0.03, x=0.07) in place of Y in high-temperature superconducting Y-Ba-Cu-O oxides. X-ray diffraction patterns confirmed that all samples had orthorhombic structures. However, the transition temperature turn Tc was 83 K for x=0.03 in sample 1, 84 K for x=0.07 in sample 1 and 88 K for both x=0.03 and x=0.07 in sample 2. (author) An emissive probe was designed and manufactured to measure the floating and the space potentials of a plasma in the wake region. The 'floating potential method', among various schemes, was used for the measurement and analysis. To generate the wake, a plane artificial satellite with a circular shape was introduced into a simply discharged argon plasma without a magnetic field. Potentials along the radial direction in and out of the wake region of the artificial satellite were measured, and the plasma parameters were compared in both regions. In the wake region, the floating potential was higher than that out of the wake; the space potential was approximately equal to that out of the wake; when a positive voltage was applied to the artificial satellite, the floating and the space potentials were lower than those out of the wake; and when a negative voltage was applied to the artificial satellite, the floating potential was higher and the space potential was lower than the corresponding potentials out of the wake. (author)

  6. Electron spectroscopy on high-temperature superconductors and related compounds

    International Nuclear Information System (INIS)

    Knupfer, M.

    1994-01-01

    In the last two classes of materials have been discovered which distinguish themselves due to a transition into the superconducting state at relatively high temperatures. These are the cuprate superconductors and the alkali metal doped fullerenes. In this work the electronic structure of representatives of these materials, undoped and Ca-doped YBa 2 Cu 4 O 8 and A 3 C 60 (A=K, Rb), has been investigated using electron energy-loss spectroscopy and photoemission spectroscopy. (orig.) [de

  7. Electronic components with yttrium- and bismuth-based high-Tc superconductors

    International Nuclear Information System (INIS)

    Daginnus, M.; Guettler, B.

    1992-01-01

    This project investigates the fabrication of microwave components by use of high-Tc superconductors. Detailed descriptions are given of the manufacturing and use of active Y-Ba-Cu-O components. The surface resistance of thin films used in high-quality passive microwave components such as resonators and filters is measured and optimized. (orig./MM) [de

  8. Anomalous behavior of spin fluctuations in polycrystalline NdBa_2Cu_3O_7-δ

    Science.gov (United States)

    Abdelrazek, M. M.; Reyes, A. P.; Kuhns, P. L.; Moulton, W. G.; Halperin, W. P.; Kishio, K.

    2001-03-01

    Critical slowing down of Nd spin fluctuations have been observed in 92K superconductor NdBa_2Cu_3O_7-δ at temperatures well below Tc and orders of magnitude higher than TN ( ~0.5K). Nuclear spin-lattice relaxation rate 1/T1 at the planar O(2,3) and bridging O(4) oxygen sites have been measured as a function of temperature in fields up to 37T. Data is characterized by an extremely fast relaxation, roughly two orders of magnitude larger than those of YBCO, suggestive of Nd origin. The temperature dependence shows neither Tc nor the pseudo-gap but rather a well-defined field-dependent peak for both sites. Preliminary analysis suggests 1/T1 follows the typical behavior of freezing of spin fluctuations, when the inverse correlation time of the Nd spins τc becomes comparable to NMR frequency, ω τc ~ 1. The field dependence originates from the tail of the power spectrum beyond the 1/τc cutoff. The implications of these results to superconductivity in these systems will be discussed.

  9. Flux pinning landscape up to 25 T in SmBa2Cu3O y films with BaHfO3 nanorods fabricated by low-temperature growth technique

    Science.gov (United States)

    Tsuchiya, Yuji; Miura, Shun; Awaji, Satoshi; Ichino, Yusuke; Matsumoto, Kaname; Izumi, Teruo; Watanabe, Kazuo; Yoshida, Yutaka

    2017-10-01

    REBa2Cu3O y superconducting tapes are appropriate for high field magnet applications at low temperatures (i.e. below liquid nitrogen temperature). To clarify the morphology and the volume of the effective pinning center at low temperatures, we used a low-temperature growth technique to fabricate SmBa2Cu3O y (SmBCO) films with various amounts of BaHfO3 (BHO) nanorods onto MgO-buffered metal substrates produced by ion-beam-assisted deposition; we investigated their flux pinning properties using a 25 T cryogen-free superconducting magnet that was recently developed at Tohoku University. According to the microstructural analysis using transmission electron microscopy, the BHO nanorods have a content-dependent morphology and are aligned for the higher content. The inclined and discontinuous BHO nanorods were observed in SmBCO films with BHO contents up to 3.8 vol%; they show an excellent flux pinning force density (1.5 TN m-3 at 21 T and 4.2 K) even when the magnetic field is perpendicular to the films. Based on the effective mass model for the flux pinning, the random pinning centers are dominant at low temperatures. The correlated flux pinning is stronger for aligned nanorods; however, the random pinning center becomes weaker in the 4.5 vol% BHO-doped films. Therefore, the optimal BHO doping level is approximately 3.8 vol% in terms of the amplitude of the critical current density and the anisotropy from 4.2 K to 20 K because this provides the best mixture of correlated and random flux pinning centers.

  10. Heteroepitaxial growth of Ba1 - xSrxTiO3/YBa2Cu3O7 - x by plasma-enhanced metalorganic chemical vapor deposition

    Science.gov (United States)

    Chern, C. S.; Liang, S.; Shi, Z. Q.; Yoon, S.; Safari, A.; Lu, P.; Kear, B. H.; Goodreau, B. H.; Marks, T. J.; Hou, S. Y.

    1994-06-01

    Epitaxial Ba1-xSrxTiO3(BST)/YBa2Cu3O7-x heterostructures with superior electrical and dielectric properties have been fabricated by plasma-enhanced metalorganic chemical vapor deposition (PE-MOCVD). Data of x-ray diffraction and high resolution transmission electron microscopy showed that oriented Ba1-xSrxTiO3 layers were epitaxially deposited on epitaxial (001) YBa2Cu3O7-x layers. The leakage current density through the Ba1-xSrxTiO3 films was about 10-7 A/cm2 at 2 V (about 2×105 V/cm) operation. Moreover, the results of capacitance-temperature measurements showed that the PE-MOCVD Ba1-xSrxTiO3 films had Curie temperatures of about 30 °C and a peak dielectric constant of 600 at zero bias voltage. The Rutherford backscattering spectrometry and x-ray diffraction results showed that the BST film composition was controlled between Ba0.75Sr0.25TiO3 and Ba0.8Sr0.2TiO3. The structural and electrical properties of the Ba1-xSrxTiO3/YBa2Cu3O7-x heterostructure indicated that conductive oxide materials with close lattice to Ba1-xSrxTiO3 can be good candidates for the bottom electrode.

  11. Study of Ca-substitution on YBa2Cu4O8 superconductors by positron lifetime spectrum

    International Nuclear Information System (INIS)

    Cheng Guosheng; Shang Jiaxing; Dai Xianqi

    1995-01-01

    Positron lifetime spectra were studied for Y 1-x Ca x Ba 2 Cu 4 O 8 (x 0.00-0.15) superconductors. The local electron density n e and vacancy concentration C υ were evaluated as a function of Casubstitution content x. A peak appears near x = 0.1 which just correspond to maxmium T c value. The characteristic of positron annihilation and the correlation with superconductivity were also discussed

  12. DC Magnetron sputtering of Y-Ba-Cu-O thin films

    International Nuclear Information System (INIS)

    Larsson, Gunnar.

    1990-01-01

    I have been studying dc magnetron sputtering of thin film YBa 2 Cu 3 O 6+x , one of the recently discovered high- temperatures superconductors. In the introduction a brief review of the subjects sputtering and superconductivity is given. Since partial pressure measurements, especially for oxygen, have been important in the work I include a short description of the operating principles of mass spectroscopy. Experimental results in addition to what is given in the papers concerning plasma are presented in an appendix at the end of the introduction. (au)

  13. A determination of the oxygen non-stoichiometry of the oxygen storage materials LnBaMn{sub 2}O{sub 5+δ} (Ln=Gd, Pr)

    Energy Technology Data Exchange (ETDEWEB)

    Jeamjumnunja, Kannika; Gong, Wenquan; Makarenko, Tatyana; Jacobson, Allan J., E-mail: ajjacob@uh.edu

    2016-07-15

    The A-site ordered double-perovskite oxides, LnBaMn{sub 2}O{sub 5+δ} (Ln=Gd, Pr), were synthesized and investigated to understand the effect of A site cation substitution on the oxygen storage properties of these materials. The present results are compared with our previous data for YBaMn{sub 2}O{sub 5+δ}. The results clearly reveal that changing the Ln cation strongly influences the oxidation/reduction behavior of LnBaMn{sub 2}O{sub 5+δ}. Based on thermogravimetric analysis data, oxygen uptake begins at lower temperatures in both air and oxygen in compounds with Ln{sup 3+} ions larger than Y{sup 3+}. These oxides exhibit almost complete and reversible oxygen uptake/release between fully-reduced LnBaMn{sub 2}O{sub 5} and fully-oxidized LnBaMn{sub 2}O{sub 6} during changes of the oxygen partial pressure between air and 1.99% H{sub 2}/Ar. In addition, the oxygen non-stoichiometries of GdBaMn{sub 2}O{sub 5+δ} and PrBaMn{sub 2}O{sub 5+δ} were determined as a function of pO{sub 2} at 600, 650, 700 and 750 °C by Coulometric titration at near-equilibrium conditions. The results confirm that these materials have two distinct phases on oxidation/reduction with δ≈0, 0.5 and a third phase with a range of composition with an oxygen content (5+δ) approaching ~6. The stabilities of the LnBaMn{sub 2}O{sub 5+δ} phases extend over a wide range of oxygen partial pressures (∼10{sup −25}≤pO{sub 2} (atm)≤∼1) depending on temperature. Isothermal experiments show that the larger the Ln{sup 3+} cation the lower pO{sub 2} for phase conversion. At some temperatures and pO{sub 2} conditions, the LnBaMn{sub 2}O{sub 5+δ} compounds are unstable with respect to decomposition to BaMnO{sub 3−δ} and LnMnO{sub 3}. This instability is more apparent in Coulometric titration experiments than in thermogravimetric analysis. The Coulometric titration experiments are necessarily slow in order to achieve equilibrium oxygen compositions. - Graphical abstract: Structure of LnBa

  14. Low temperature X-ray imaging of magnetic flux patterns in high temperature superconductors

    Science.gov (United States)

    Stahl, Claudia; Ruoß, Stephen; Weigand, Markus; Bechtel, Michael; Schütz, Gisela; Albrecht, Joachim

    2015-05-01

    We present X-ray magnetic circular dichroism (XMCD) microscopy results obtained at liquid nitrogen temperatures on the high-Tc superconductor YBCO (YBa2Cu3O7-δ). The magnetic flux distribution arising from electric currents in the superconductor is detected and visualized using soft-magnetic Co40Fe40B20 (CoFeB) as sensor layer and XMCD as contrast mechanism. It has been shown that the XMCD contrast in the sensor layer directly corresponds to magnetic flux distribution of the superconductor and hence can be used to image magnetic structures in superconductors [Stahl et al., Phys. Rev. B 90, 104515 (2014)]. The existing scanning UHV X-ray microscopy setup MAXYMUS at the synchrotron BESSY II in Berlin has been upgraded for that purpose: we use a nitrogen based MMR Micro Miniature Joule-Thompson Cryostat with temperature range from 75 K to 580 K. The capability of the method is demonstrated on two different superconducting samples, an optimally doped thin film and a melt-textured block.

  15. Magnetic field effect on the electrical resistivity of Y1-xNixBa2Cu3O7-δ superconductor

    Science.gov (United States)

    Hadi-Sichani, Behnaz; Shakeripour, Hamideh; Salamati, Hadi

    2018-06-01

    The Ni- substituted Y1-xNixBa2Cu3O7-δ high temperature superconducting samples with 0 ≤ x zero to 1 Tesla, applied perpendicular to the current direction. To study of magnetoresistance is one of the most important ways to investigate the intergranular nature of superconducting materials. The resistive transition is made of two parts. The first- unaffected to applied magnetic field part which is near the onset of superconductivity. This region is due to superconductivity in grains. The second- broaden tail part which is due to the connectivity of the grains. At temperatures close to Tc 0, (ρ = 0), under applied magnetic fields, weak links are affected and the vortices are penetrated and move inside the intergranular and then the tail part is broaden. This broadening part observed in the electrical resistivity, ρ(T), and in the derivative of the electrical resistivity, dρ/dT, becomes too small or even absent in Ni doped samples. For pure sample, Tc 0 was around 90 K; by applying a magnetic field H = 0.3 T it shifted to 40 K. This broadening is 91.4 K to 80 K for x = 0.002 and 91.7 K to 85 K for x = 0.004 samples. We found an optimal value of Ni doping concentration which improves the coupling of the grains. Then, vortices get strongly pinned. These observations suggest that the Ni substitution can reduce the weak links and increase the Jc values of these superconductors.

  16. Hole filling and interlayer coupling in YBa2Cu3O7/PrBa2Cu3O7 superlattices

    International Nuclear Information System (INIS)

    Biagini, M.; Calandra, C.; Ossicini, S.

    1995-01-01

    Charge transfer effects in YBa 2 Cu 3 O 7 /PrBa 2 Cu 3 O 7 superlattices have been proposed by many authors as the origin of the experimentally observed strong depression of the critical temperature. We performed self-consistent LMTO-ASA calculations and found that no remarkable change in the electronic structure of the superconducting CuO 2 planes occurs in the studied structures, when the PBCO layer thickness is varied. The observed depression of the critical temperature does not seem to be originated intrinsically by a severe modification of the electronic structure or by the hole-filling mechanism. (orig.)

  17. Study of magnetic excitations in the high critical temperature La2-xSrxCuO4 superconductor with neutrons inelastic scattering

    International Nuclear Information System (INIS)

    Petit, S.

    1997-01-01

    In this work, we question the relevance of spin correlations in the problem of high-T c superconductivity. To characterize these correlations, we present a detailed inelastic neutron scattering study of the magnetic excitations spectrum, in the high T c La 2-x Sr x CuO 4 copper oxide superconductor, as a function of temperature and strontium content x. Our study demonstrates the existence of two distinct types of fluctuations. The first type corresponds to two-dimensional isotropic fluctuations peaked at incommensurate points around the antiferromagnetic wavevector. These fluctuations show a gap below T c . The second type of fluctuations corresponds to two-dimensional very low energy, typically 1 MeV, antiferromagnetic correlations. They arise at low temperatures, for T ≤T f ∼ 10 K ≤T c . Different scenarios are discussed, namely particle-hole excitation arising because of nesting properties of the Fermi surface, stripes, and localized carriers in the CuO 2 plane because of the La/Sr substitution disorder. Next, aiming to study the interrelation between magnetism and superconductivity, we present a theoretical perturbative treatment of the t-t'-J model. This model is believed to describe the physics of the CuO 2 plane. The considered quasiparticles describe the motion of a doped hole, followed by localized spins on the copper sites. For a given doping x, two phases can exist, containing either x or 1 + x of these quasiparticles. We show at in the second phase, the exchange interaction between localized spins, combined to the intrinsic anharmonicity of these quasiparticles leads to an attractive interaction between them. We study the stability and the symmetry of a superconducting phase based on this mechanism. (author)

  18. Pairing transition, coherence transition, and the irreversibility line in granular GdBa2Cu3O7-δ

    Science.gov (United States)

    Roa-Rojas, J.; Menegotto Costa, R.; Pureur, P.; Prieto, P.

    2000-05-01

    We report on electrical magnetoconductivity experiments near the superconducting transition of a granular sample of GdBa2Cu3O7-δ. The measurements were performed in magnetic fields ranging from 0 to 500 Oe applied parallel to the current orientation. The results show that the transition proceeds in two steps. When the temperature is decreased we first observe the pairing transition, which stabilizes superconductivity within the grains at a temperature practically coincident with the bulk critical temperature Tc. Analysis of the fluctuation contributions to the conductivity shows that the universality class for this transition is that of the three dimensional (3D)-XY model in the ordered case, with dynamic critical exponent z=3/2. Close to the zero-resistance state, the measurements reveal the occurrence of a coherence transition, where the phases of the order parameter in individual grains become long-range ordered. The critical temperature Tco for this transition is close to the point where the resistivity vanishes. A strong enlargement of the fluctuation interval preceding the coherence transition is caused by the applied magnetic field. In this region, a 3D-Gaussian regime and an asymptotic critical regime were clearly identified. The critical conductivity behavior for the coherence transition is interpreted within a 3D-XY model where disorder and frustration are relevant. The irreversibility line is determined from magnetoconductivity measurements performed according to the zero-field-cooled (ZFC) and field-cooled data collected on cooling (FCC) recipes. The locus of this line coincides with the upper temperature limit for the fluctuation region above the coherence transition. The irreversibility line is interpreted as an effect of the formation of small clusters with closed loops of Josephson-coupled grains.

  19. Correlation between in-field critical currents in Zr-added (Gd, Y)Ba2Cu3Ox superconducting tapes at 30 and 77 K

    Energy Technology Data Exchange (ETDEWEB)

    Selvamanickam, V; Xu, A; Liu, Y; Khatri, ND; Lei, C; Chen, Y; Galstyan, E; Majkic, G

    2014-03-11

    Critical current (I-c) values of 1384 Lambda/12 mm, corresponding to a critical current density of 12.47 MA cm(-2) and a pinning force of 374 GN m(-3), have been achieved at 30 K, 3 T in the orientation of field parallel to the c axis (B parallel to c) in (Gd, Y)BaCuO tapes with 15 mol% Zr addition made by metal organic chemical vapor deposition (MOCVD). These tapes show pinning force levels as high as 453 GN m(-3) at 30 K. An analysis of the properties of 24-28 (Gd, Y)BaCuO tapes with 15 mol% Zr addition showed a lack of correlation between their critical currents at 30 K, 3 T (B parallel to c) and I-c values both at 77 K, zero field and at 77 K, 1 T (B parallel to c). However, a strong correlation was found between the critical currents at 30 K, 3 T and at 77 K, 3 T (B parallel to c). It has also been discovered that the minimum critical current (I-c, (min)) value at 77 K, 3 T has no influence on the I-c,I- (min) value at 30 K, 3 T, and it in turn depends on the ratio of the I-c values in the orientations of field parallel and perpendicular to the c axis at 77 K, 3 T.

  20. Obtention of superconductivity by room temperature electrochemical oxidation of La2CuO4

    International Nuclear Information System (INIS)

    Casan-Pastor, N.; Fuertes, A.; Gomez-Romero, P.

    1993-01-01

    The undoped oxide La2CuO4 has required traditionally synthesis under high pressure of oxygen (and high temperatures) to incorporate excess oxygen into its structure and become a superconductor. The electrochemical oxidation of this same oxide at room temperature and pressure constitutes a striking example of the use of an alternative driving force for the oxidation of oxides to become superconductors. Electrochemical treatment of oxides has been frequently applied to their reduction with cationic intercalation. Oxidations of these solid with the concomitant intercalation of anions into their lattice shows also great promises. The paper reports recent results in the electrochemical oxidation of La2CuO4 and other cuprates, showing also the important role of post-oxidation thermal treatments on the properties of the resulting solids

  1. Effect of Sintering Time on Superconducting Wire Bi-Pb-Sr-Ca-Cu-O With Dopant MgO Sheated Ag Using Powder in Tube Method

    Directory of Open Access Journals (Sweden)

    Hariyati Lubis

    2018-01-01

      DAFTAR PUSTAKA Abbas M.M., Abass L.K and Salman U., (2012, Influences of Sintering Time on the Tc of Bi2-xCuxPb0.3Sr2Ca2Cu3010+ High Temperature Superconductors, Energy Procedia 18, 215-224  Abbas, M.M., Abbas, L.K., Bahedh, H.S. 2015. Superconducting Properties of Bi2-SbxPb0,3Sr1,9Ba0,1Ca2Cu3O10+δ Compounds. Journal of Applied Science Research. 11. 22: 164-172 Darsono, N., Imaduddin, A., Raju, K., Yoon, D.H., (2015, Synthesis and Characterization of Bi1.6Pb0.4Sr2Ca2Cu3O7 Superconducting Oxide by High-Energy Milling, J Supercond Nov Magn. E. Chew,. (2010, Superconducting Transformer Design And Construction, University of Canterbury, Christchurch, New Zealand. March Hamadneh, I., Halim, S. A., dan Lee, C. K., (2006,  Characterization of Bi1.6Pb0.4Sr2Ca2Cu3Oy Ceramic Superconductor Prepared Via Coprecipitation Method at Different Sintering Time, J. Mater. Sci, 41: 5526-5530. Hermiz G.Y., Aljurani B.A., Beayaty M.A., (2014, Effect of Mn Substitution on the Superconducting Properties of Bi1.7Pb0,3Sr2Ca2-xMnxCu3O10+, International Journal Of Engineering and Advanced Technology (IJEAT. 3. 4: 213-217 John R Hull, (2003, Applications of high-temperature superconductors in power technology, Reports on Progress in Physics, Volume 66, Number 11 Lu, X.Y., Yi, D., Chen, H., Nagata, A. 2016. Effect of Sn, MgO and Ag2O mix-doping on the formation and superconducting properties of Bi-2223 Ag/tapes. Physics Procedia. 81: 129-132 Meretliev Sh., Sadykov K.B., Berkeliev A., (2000, Doping of High Temperature Superconductors, Turk J Phy.24: 39-48 Mohammed, N. H., Ramadhan A., Ali I. A., Ibrahim, I. H., dan Hassan, M. S, (2012, Optimizing the Preparation Conditions of Bi-2223 Superconducting Phase Using PbO and PbO2, Materials Sciences and Applications, 3: 224-233. Roumie, M., Marhaba, S., Awad R., Kork M., Hassan I., Mawassi R., (2014, Effect of Fe2O3 Nano-Oxide Addition on the Superconducting Properties of the (Bi,Pb-2223 Phase, Journal of Supercond Nov Magn, 27: 143-153 Serkan

  2. Superconductivity at 108 K in the simplest non-toxic double-layer cuprate of Ba2CaCu2O4(O,F)2

    International Nuclear Information System (INIS)

    Shirage, P M; Shivagan, D D; Crisan, A; Tanaka, Y; Kodama, Y; Kito, H; Iyo, A

    2008-01-01

    We report the superconductivity in apical fluorine system of Ba 2 CaCu 2 O 6-y F y : the second member of Ba 2 Ca n-1 Cu n O 2n (O,F) 2 homologous series. The polycrystalline samples of Ba 2 CaCu 2 O 6-y F y (F-0212) were synthesized under high pressure as a parameter of nominal fluorine content (y). Samples with y = 2.0 ∼ 1.2 elucidating the very sharp superconducting transitions in temperature dependence of susceptibility from under doping state to slightly over doping state via optimal doping state. A remarkable highest T c of 108 K has been achieved for the sample synthesized from a nominal composition of Ba 2 CaCu 2 O 4.4 F 1.6 . This T c is highest among the double CuO 2 layered system except for that including toxic elements such as Hg and T1. The T c has been systematically controlled from 57 K to 108 K by controlling the doping state, by designing the starting composition of fluorine and oxygen. The strong dependence of the 'a' and 'c' lattice constants were found on the nominal F content. We propose the Ba 2 CaCu 2 O 4 (O,F) 2 as a promising material for practical use due to its high T c and non-toxicity with a simple crystal structure

  3. Advantageous grain boundaries in iron pnictide superconductors

    Science.gov (United States)

    Katase, Takayoshi; Ishimaru, Yoshihiro; Tsukamoto, Akira; Hiramatsu, Hidenori; Kamiya, Toshio; Tanabe, Keiichi; Hosono, Hideo

    2011-01-01

    High critical temperature superconductors have zero power consumption and could be used to produce ideal electric power lines. The principal obstacle in fabricating superconducting wires and tapes is grain boundaries—the misalignment of crystalline orientations at grain boundaries, which is unavoidable for polycrystals, largely deteriorates critical current density. Here we report that high critical temperature iron pnictide superconductors have advantages over cuprates with respect to these grain boundary issues. The transport properties through well-defined bicrystal grain boundary junctions with various misorientation angles (θGB) were systematically investigated for cobalt-doped BaFe2As2 (BaFe2As2:Co) epitaxial films fabricated on bicrystal substrates. The critical current density through bicrystal grain boundary (JcBGB) remained high (>1 MA cm−2) and nearly constant up to a critical angle θc of ∼9°, which is substantially larger than the θc of ∼5° for YBa2Cu3O7–δ. Even at θGB>θc, the decay of JcBGB was much slower than that of YBa2Cu3O7–δ. PMID:21811238

  4. PRODUCCIÓN Y CARACTERIZACIÓN DEL NUEVO SISTEMA SUPERCONDUCTOR Yb0,5Ho0,5Ba2Cu3O7-d

    Directory of Open Access Journals (Sweden)

    Jully P. Peña

    2011-01-01

    Full Text Available Se reporta la caracterización del nuevo sistema superconductor Yb0,5Ho0,5Ba2Cu3O7-δ perteneciente a la familia de cupratos de alta temperatura TR123; el material fue producido utilizando el método de reacción de estado sólido (SSR con una temperatura de sinterizado de 910 °C. Se muestra la caracterización morfológica referente al comportamiento granular utilizando la técnica de Microscopía electrónica de barrido (SEM; la caracterización estructural, se logra sometiendo la muestra a difracción de rayos X (DRX y se obtienen los parámetros estructurales implementando el método de refinamiento Rietveld en el software GSAS, el material resulta poseer celdas unitarias ortorrómbicas tipo perovskita con un comportamiento superconductor que se evidencia en la curva de resistividad como función de la temperatura cuya derivada presenta un punto crítico en el valor correspondiente a la temperatura crítica Tc 92,61 K.

  5. Development of application technique of bulk high-Tc superconductor

    International Nuclear Information System (INIS)

    Hong, Kye Won; Kim, Chan Joong; Kim, Kee Baek; Kwon, Sun Chil; Won, Dong Yun; Lee, Hoh Jin; Lee, Heui Kyoon; Jang, Kun Ik; Yang, Suk Woo

    1995-03-01

    YBCO-Ag composite superconductors were prepared by extrusion using inorganic binder materials. In the case of the undoped 1-2-3 sample with a dia. of 2.5 mm, critical current density (Jc) was 150 A/cm 2 and current density (Ic) was 10 amps. In the case of the sample with a die. of 4.5 mm, meanwhile, Jc and Ic were 50 A/cm 2 and 32 amps, respectively. Influence of BaCeO 3 addition on magnetization characteristics of melt-textured Y-Ba-Cu-O superconductor was investigated. The variation of magnetization behavior due to the addition of BaCeO 3 is discussed on the basis of the related microstructures. 37 figs, 1 tab, 56 refs. (Author)

  6. High temperature-induced phase transitions in Sr2GdRuO6 complex perovskite

    International Nuclear Information System (INIS)

    Triana, C.A.; Corredor, L.T.; Landínez Téllez, D.A.; Roa-Rojas, J.

    2011-01-01

    Highlights: ► Crystal structure, thermal expansion and phase transitions at high-temperature of Sr 2 GdRuO 6 perovskite has been investigated. ► X-ray diffraction pattern at 298 K of Sr 2 GdRuO 6 corresponds to monoclinic perovskite-type structure with P2 1 /n space group. ► Evolution of X-ray diffraction patterns at high-temperature shows that the Sr 2 GdRuO 6 perovskite suffers two-phase transitions. ► At 573 K the X-ray diffraction pattern of Sr 2 GdRuO 6 corresponds to monoclinic perovskite-type structure with I2/m space group. ► At 1273 K the Sr 2 GdRuO 6 perovskite suffers a complete phase-transition from monoclinic I2/m (no. 12) to tetragonal I4/m (no. 87). -- Abstract: The crystal structure behavior of the Sr 2 GdRuO 6 complex perovskite at high-temperature has been investigated over a wide temperature range between 298 K ≤ T ≤ 1273 K. Measurements of X-ray diffraction at room-temperature and Rietveld analysis of the experimental patterns show that this compound crystallizes in a monoclinic perovskite-like structure, which belongs to the P2 1 /n (no. 14) space group and 1:1 ordered arrangement of Ru 5+ and Gd 3+ cations over the six-coordinate M sites. Experimental lattice parameters were obtained to be a =5.8103(5) Å, b =5.8234(1) Å, c =8.2193(9) Å, V = 278.11(2) Å 3 and angle β = 90.310(5)°. The high-temperature analysis shows the occurrence of two-phase transitions on this material. First, at 573 K it adopts a monoclinic perovskite-type structure with I2/m (no. 12) space group with lattice parameters a = 5.8275(6) Å, b = 5.8326(3) Å, c = 8.2449(2) Å, V = 280.31(3) Å 3 and angle β = 90.251(3)°. Close to 1273 K it undergoes a complete phase-transition from monoclinic I2/m (no. 12) to tetragonal I4/m (no. 87), with lattice parameters a = 5.8726(1) Å, c = 8.3051(4) Å, V = 286.39(8) Å 3 and angle β = 90.0°. The high-temperature phase transition from monoclinic I2/m (no. 12) to tetragonal I4/m (no. 87) is characterized

  7. Structure and properties of YBa2Cu3O7-δ superconductor doped with bulk cadmium oxide

    Directory of Open Access Journals (Sweden)

    A Echresh

    2010-09-01

    Full Text Available In this paper, the Y1-xCdxBa2Cu3O7-δ superconductor with x=0, 0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5 are prepared using the solid state method and the structure, electrical resistance, critical current density and critical temperature of it, have been studied. The results show that these doping do not affect so much on the structure and lattice parameters. The electrical resistance of samples increased with doping. A little amount of doping cadmium improve critical current density such that the sample x=0.1 has a maximum critical current density among the samples. The critical temperature with doping cadmium up to x=0.2 has little fluctuation and its variation can be ignored, but by increasing up to x=0.5 the critical temperature decreases gradually.

  8. High-temperature superconducting oxide synthesis and the chemical doping of the Cu-O planes

    International Nuclear Information System (INIS)

    Tarascon, J.M.; Barboux, P.; Bagley, B.G.; Greene, L.H.; McKinnon, W.R.; Hull, G.W.

    1987-01-01

    Different synthesis techniques for the preparation of dense superconducting ceramics are discussed, and a sol-gel process is shown to be very promising. The effect of oxygen content, and the effect of substitution of Ni and Zn for copper, on the structural, transport and superconducting properties of the La-Sr-Cu-O and Y-Ba-Cu-O systems are presented. The authors find that substitution on the copper sites destroys T/sub c/ in the La-Sr-Cu-O system and decreases it in the Y-Ba-Cu-O system, and this effect is insensitive as to whether the 3d metal is magnetic (Ni) or diamagnetic (Zn). A detailed study of the YBa/sub 2/Cu/sub 3/O/sub 7-y/ system as a function of oxygen content (y) shows that superconductivity can be destroyed in these materials by the removal of oxygen and restored by reinjecting oxygen; either thermally at 500 0 C or at temperatures (80 0 C) compatible with device processing by means of a novel plasma oxidation process. Of scientific interest, the plasma process induces bulk superconductivity in the undoped La/sub 2/CuO/sub 4/

  9. Thickness Dependence of Magnetic Relaxation and E-J Characteristics in Superconducting (Gd-Y)-Ba-Cu-O Films with Strong Vortex Pinning

    Energy Technology Data Exchange (ETDEWEB)

    Polat, Ozgur [ORNL; Sinclair IV, John W [ORNL; Zuev, Yuri L [ORNL; Thompson, James R [ORNL; Christen, David K [ORNL; Cook, Sylvester W [ORNL; Kumar, Dhananjay [ORNL; Chen, Y [SuperPower Incorporated, Schenectady, New York; Selvamanickam, V. [SuperPower Incorporated, Schenectady, New York

    2011-01-01

    The dependence of the critical current density Jc on temperature, magnetic field, and film thickness has been investigated in (Gd-Y)BaCu-oxide materials of 0.7, 1.4, and 2.8 m thickness. Generally, the Jc decreases with film thickness at investigated temperatures and magnetic fields. The nature and strength of the pinning centers for vortices have been identified through angular and temperature measurements, respectively. These films do not exhibit c-axis correlated vortex pinning, but do have correlated defects oriented near the ab-planes. For all film thicknesses studied, strong pinning dominates at most temperatures. The vortex dynamics were investigated through magnetic relaxation studies in the temperature range of 5 77 K in 1 T and 3 T applied magnetic fields, H || surface-normal. The creep rate S is thickness dependent at high temperatures, implying that the pinning energy is also thickness dependent. Maley analyses of the relaxation data show an inverse power law variation for the effective pinning energy Ueff ~ (J0/J) . Finally, the electric field-current density (E-J) characteristics were determined over a wide range of dissipation by combining experimental results from transport, swept field magnetometry (VSM), and Superconducting Quantum Interference Device (SQUID) magnetometry. We develop a self-consistent model of the combined experimental results, leading to an estimation of the critical current density Jc0(T) in the absence of flux creep.

  10. Far-infrared spectra of polycrystalline Ba2YCu3O/sub 9-//sub δ/

    International Nuclear Information System (INIS)

    Thomas, G.A.; Ng, H.K.; Millis, A.J.; Bhatt, R.N.; Cava, R.J.; Rietman, E.A.; Johnson, D.W. Jr.; Espinosa, G.P.; Vandenberg, J.M.

    1987-01-01

    We present far-infrared reflectivity spectra of seven samples of ceramic superconductors in the Ba-Y-Cu-O system with transition temperatures near 93 K. We find superconducting gap structures on the basis of which we estimate the ratio of twice the average gap to the transition temperature to be consistent with 3.5, but possibly higher. Questions of normal-state characterization preclude a definitive analysis

  11. Raman studies of lanthanum cuprate superconductors

    International Nuclear Information System (INIS)

    Weber, W.H.; Peters, C.R.; Logothetis, E.M.

    1989-01-01

    Raman-scattering studies of the high-T/sub c/ superconductor La/sub 2-//sub x/(Sr, Ba)/sub x/CuO 4 are briefly reviewed. A detailed analysis of the phonon-mode symmetries is given along with a discussion of the effects expected from the orthorhombic-to-tetragonal phase transition, which is known to occur in these materials. Survey spectra are given for powders, ceramics, and single crystals, and an oxide of Cu is identified as the primary impurity phase. Extensive spectra are given from oriented single crystals of La 2 CuO 4 and La/sub 1.85/Sr/sub 0.15/CuO 4 , and several mode assignments are made. Spectra for the high-temperature tetragonal phase and the low-temperature orthorhombic phase are given for each material. The soft phonon associated with the phase transition is seen in La 2 CuO 4 as is a broad peak arising from two-magnon scattering. Neither of these features is seen in the Sr-doped sample

  12. Tl Cuprate Superconductors Studied by XPS

    Energy Technology Data Exchange (ETDEWEB)

    Vasquez, R. P. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099 (United States); Siegal, M. P. [Sandia National Laboratories, Albuquerque, NM 87185-1421 (United States); Overmyer, D. L. [Sandia National Laboratories, Albuquerque, NM 87185-1421 (United States); Ren, Z. F. [Department of Chemistry, State University of New York, Buffalo, NY 14260-3000 (United States); Lao, J. Y. [Department of Chemistry, State University of New York, Buffalo, NY 14260-3000 (United States); Wang, J. H. [Department of Chemistry, State University of New York, Buffalo, NY 14260-3000 (United States)

    1999-07-01

    XPS measurements on epitaxial thin films of the Tl cuprate superconductors Tl2Ba2CaCu2O8, Tl2Ba2Ca2Cu3O10, and Tl0.78Bi0.22Ba0.4Sr1.6Ca2Cu3O9-{delta} are presented. These data, together with previous measurements in this lab on Tl2Ba2CuO6-{delta} and TlBa2CaCu2O7-{delta}, comprise a comprehensive data set for comparison of Tl cuprates in which the number of Tl-O and Cu-O layers, and hence the chemical and electronic properties, vary. (c) 2000 American Vacuum Society.

  13. Tl Cuprate Superconductors Studied by XPS

    International Nuclear Information System (INIS)

    Vasquez, R. P.; Siegal, M. P.; Overmyer, D. L.; Ren, Z. F.; Lao, J. Y.; Wang, J. H.

    1999-01-01

    XPS measurements on epitaxial thin films of the Tl cuprate superconductors Tl2Ba2CaCu2O8, Tl2Ba2Ca2Cu3O10, and Tl0.78Bi0.22Ba0.4Sr1.6Ca2Cu3O9-δ are presented. These data, together with previous measurements in this lab on Tl2Ba2CuO6-δ and TlBa2CaCu2O7-δ, comprise a comprehensive data set for comparison of Tl cuprates in which the number of Tl-O and Cu-O layers, and hence the chemical and electronic properties, vary. (c) 2000 American Vacuum Society

  14. An unusual isotope effect in a high-transition-temperature superconductor

    International Nuclear Information System (INIS)

    Gweon, G.-H.; Sasagawa, T.; Zhou, S.Y.; Graf, J.; Takagi, H.; Lee, D.-H.; Lanzara, A.

    2004-01-01

    In conventional superconductors, the electron pairing that allows superconductivity is caused by exchange of virtual phonons, which are quanta of lattice vibration. For high-transition-temperature (high-Tc) superconductors, it is far from clear that phonons are involved in the pairing at all. For example, the negligible change in Tc of optimally doped Bi2Sr2CaCu2O8 (Bi2212) upon oxygen isotope substitution (16O to 18O leads to Tc decreasing from 92 to 91 K) has often been taken to mean that phonons play an insignificant role in this material. Here we provide a detailed comparison of the electron dynamics of Bi2212 samples containing different oxygen isotopes, using angle-resolved photoemission spectroscopy. Our data show definite and strong isotope effects. Surprisingly, the effects mainly appear in broad high-energy humps, commonly referred to as ''incoherent peaks''. As a function of temperature and electron momentum, the magnitude of the isotope effect closely correlates with the superconducting gap--that is, the pair binding energy. We suggest that these results can be explained in a dynamic spin-Peierls picture, where the singlet pairing of electrons and the electron-lattice coupling mutually enhance each other

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

    Science.gov (United States)

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

    2016-10-01

    Band-offsets at BaTiO3/Cu2O heterojunction and enhanced photoelectrochemical response: theory and experiment Dipika Sharmaa, Vibha R. Satsangib, Rohit Shrivastava, Umesh V. Waghmarec, Sahab Dassa aDepartment of Chemistry, Dayalbagh Educational Institute, Agra-282 110 (India) bDepartment of Physics and Computer Sciences, Dayalbagh Educational Institute, Agra-282 110 (India) cTheoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore-560 064 (India) * Phone: +91-9219695960. Fax: +91-562-2801226. E-mail: drsahabdas@gmail.com. Study on photoelectrochemical activity of pristine BaTiO3, Cu2O and BaTiO3/Cu2O heterojunction has been carried out using DFT based band offsets and charge carriers effective mass calculations and their experimental verification. The results of DFT calculations show that BaTiO3 and Cu2O have staggered type band alignment after the heterojunction formation and high mobility of electrons in Cu2O as compared to the electrons in BaTiO3. Staggered type band edges alignment and high mobility of electrons and holes improved the separation of photo-generated charge carriers in BaTiO3/Cu2O heterojunction. To validate the theoretical results experiments were carried out on pristine BaTiO3, Cu2O and BaTiO3/Cu2O heterojunction with varying thickness of Cu2O. All samples were characterized by X- Ray Diffractometer, SEM and UV-Vis spectrometry. Nanostructured thin films of pristine BaTiO3, Cu2O and BaTiO3/Cu2O heterojunction were used as photoelectrode in the photoelectrochemical cell for water splitting reaction. Maximum photocurrent density of 1.44 mA/cm2 at 0.90 V/SCE was exhibited by 442 nm thick BaTiO3/Cu2O heterojunction photoelectrode Increased photocurrent density and enhanced photoconversion efficiency, exhibited by the heterojunction may be attributed to improved conductivity and enhanced separation of the photogenerated carriers at the BaTiO3/Cu2O interface. The experimental results and first

  16. The XRD Study of the Effect of Slight Change in Structure on the Superconductivity of Y-Ba-Cu-O System Material

    Science.gov (United States)

    Huaqin, Wang; Shiyuan, Zhang; Tongzheng, Jin; Shiying, Han; Dirong, Qiu; Hao, Wang; Ningsheng, Zhou

    In this paper the differences in diffraction intensities from some crystal planes in the X-ray diffraction patterns of high Tc Y-Ba-Cu-O system superconductors prepared by different processing conditions and the difference among various structure cells in references are interpreted using computer fitting. The results suggest that there exists two structure cells in the single phase YBa2Cu3O7-x samples. Both structure cells have the same crystal symmetry and almost the same lattice parameters, a=3.821Å, b=3.892Å and c=11.676Å, but the different distortion degree of Cu2-O plane. According to EPR spectra measured on the same samples, it is considered that the improvement of superconductivity for the samples prepared by two-step annealing in flowing oxygen may be related to concentration of the structure cell with more serious distortion on the Cu2-O plane.

  17. Topotactic reduction of YBa2Cu4O8 under the electron beam

    International Nuclear Information System (INIS)

    Domenges, B.; Hervieu, M.; Raveau, B.; Karpinski, J.; Kaldis, E.; Rusiecki, S.

    1991-01-01

    The stability of the high oxygen-pressure 80K-superconductor YBa 2 Cu 4 O 8 under the electron beam was studied by high resolution electron microscopy. Several topotactic reductions were observed for which models are proposed. The most important feature deals with the topotactic transformation of YBa 2 Cu 4 O 8 into the 125-type phase Y 1+x Ba 2+2x Cu 5-3x O 9 (x = 0.14) involving order-disorder phenomena

  18. Heteroepitaxial growth of strained multilayer thin films of high-temperature superconductors

    International Nuclear Information System (INIS)

    Gross, R.; Gupta, A.; Olsson, E.; Segmueller, A.; Koren, G.

    1991-01-01

    Recently, the heteroepitaxial growth of multilayer structures of different copper oxide superconductors has been reported by several groups. In general, two different types of multilayer structures should be distinguished. The first kind of mulitlayer is formed by high-T c materials having the same crystal structure and almost the same lattice constants, as for example ReBa 2 Cu 3 O 7 (Re=rare earth) multilayers with alternating Re-elements. In these multilayers the two different rare earth copper oxides (Y/Dy, Y/Pr) have the same orthorhombic unit cell. Due to the very similar lattice constants, the misfit strain is easily accommodated without the formation of defects. The second kind of multilayer is formed by layers of materials having different crystal structure and lattice parameters. In these multilayers the misfit can be coherently accommodated below a critical modulation thickness as discussed below. This renders possible the heteroepitaxial growth of strained multilayer structures, both of two copper oxides of different crystal structure, as has been demonstrated recently for the system YBa 2 Cu 3 O 7-δ /Nd 1.83 Ce 0.17 CuO x , and of superconducting copper oxides and insulating materials. For multilayers of different copper oxides, a combination of almost all high-Tc materials should be possible, since the presence of the CuO 2 sheets in these materials results in similar lattice constants in their basal planes ('a' and 'b'). (orig./BHO)

  19. Positron annihilation at defects in sintered high Tc perovskite superconductors

    International Nuclear Information System (INIS)

    Corbel, C.; Bernede, P.; Pascard, H.; Rullier-Albenque, F.; Kormann, R.; Marucco, J.F.

    1988-01-01

    We report positron lifetime measurements in sintered superconducting YBa 2 Cu 3 O 7-x and GdBa 2 Cu 3 O 7-x oxides. It is shown that the thermal behaviour of the positron lifetime spectra strongly depends on the preparation of the ceramics. A lifetime of 190±3 ps is attributed to oxygen deficient regions. Two lifetimes of 251±7 ps and 225±5 ps are attributed to a cation vacancy presenting a temperature dependent atomic arrangement. The lifetime transition (251 → 225 ps) occurs during decreases in temperature across the resistivity superconducting transition. This lifetime change indicates that the volume of the cation vacancy decreases in the superconducting state

  20. Correlation of resistance and thermogravimetric measurements of the Er/sub 1/Ba/sub 2/Cu/sub 3/O/sub 9-δ/ superconductor to sample preparation techniques

    International Nuclear Information System (INIS)

    Lee, S.I.; Golben, J.P.; Song, Y.; Chen, X.D.; McMichael, R.D.; Gaines, J.R.

    1987-01-01

    The resistance dependence and thermogravimetric analysis (TGA) of Er/sub 1/Ba/sub 2/Cu/sub 3/O/sub 9-δ/ has been measured in the temperature range 27 C to 920 CV. The heat treatments and oxygen flow rates simulated actual sintering and annealing processes used in sample preparation. Evidence of a phase transition in Er/sub 1/Ba/sub 2/Cu/sub 3/O/sub 9-δ/ near 680 C is discussed, as well as the implications of the maximum oxygen uptake near 400 C. The impact of sample preparation procedures on sample features is also discussed

  1. Electron-gamma perturbed angular correlation studies on high-TC superconductors

    International Nuclear Information System (INIS)

    Correia, J.G.; Araujo, J.P.; Marques, J.G.; Ramos, A.R.; Lourenco, A.A.; Amaral, V.; Galindo, V.; Senateur, J.P.; Weiss, F.; Wahl, U.; Melo, A.A.; Soares, J.C.; Sousa, J.B.

    2000-01-01

    Recent results on the study of high-T C superconductors using the e - -γperturbed angular correlation technique are presented. The basic features of the experimental equipment and its installation at the ISOLDE facility are briefly described. Results obtained from 197m Hg implanted into high quality Y 1 Ba 2 Cu 3 O 6+δ epitaxy thin films are presented and discussed

  2. Preparation and characterization of Y-BA-CU-O based superconductors of varying stoichiometries

    International Nuclear Information System (INIS)

    Sarmago, R.V.

    1989-01-01

    Variations on the Y-Ba-Cu-O system were done for each element. The X-ray diffraction pattern of each variation were studied and compared. Resistance measurements for the Y=1.2 and 1.4 samples showed a complete disappearance of electrical resistance at 88K. Infrared spectrum for the different variations showed a growth or disappearance of an absorption peak near 1460 cm -1 depending on the concentration. (Auth.). 7 refs.; 12 figs.; 2 tabs

  3. Current and field distribution in high temperature superconductors

    International Nuclear Information System (INIS)

    Johnston, M.D.

    1998-01-01

    The manufacture of wires from HTS materials containing copper-oxide planes is difficult because their physical and electrical properties are highly anisotropic. The electrical connectivity depends on the nearest-neighbour grain alignment and although a high degree of grain texture is achieved through processing, the tape microstructure is generally far from uniform, with weak links and porosity also complicating the picture. In order to optimise the processing, the microstructural features common to good tapes must be identified, requiring knowledge of the local properties. The preferential path taken by transport current is determined by the properties of the local microstructure and as such can be used to measure the variation in quality across the tape cross-section. By measuring the self-field profile generated by a current-carrying tape, it is possible to extract the associated current distribution. I have designed and built a Scanning Hall Probe Microscope to measure the normal field distribution above superconductor tapes carrying DC currents, operating at liquid nitrogen temperature and zero applied magnetic field. It has a spatial resolution of 50*50 μm and a field sensitivity of 5 μT, and can scan over a distance of 6 mm. The current extraction is performed by means of a deconvolution procedure based on Legendre functions. This allows a nondestructive, non-invasive method of evaluating the effects of the processing on the tapes - especially when correlated with transport and magnetisation measurement data. Conductors fabricated from Bi 2 Sr 2 Ca 2 Cu 3 O 10 , Bi 2 Sr 2 CaCu 2 O 8 and (Tl 0.78 Bi 0.22 )(Sr 0.8 Ba 0.2 ) 2 Ca 2 Cu 3 O x , have been investigated. I have confirmed the reports that in Bi-2223/Ag mono-core conductors produced by the oxide-powder-in-tube (OPIT) technique, the current flows predominantly at the edges of the tape, where the grains are long and well-aligned. This is in contrast to Bi-2212 ribbons, where the better microstructure

  4. Direct measurement of the Cu oxidation number of cuprate superconductor ceramics

    International Nuclear Information System (INIS)

    Dankhazi, Z.; Szasz, A.; Kojnok, J.; Gal, M.; Torkos, K.; Solymos, K.; Kirchmayr, H.; Mueller, H.; Watson, L.M.

    1991-01-01

    The Cu oxidation number of YBa 2 Cu 3 O 7 was measured directly by soft X-ray fluorescent spectroscopy both at room temperature and at liquid N 2 temperature. The measurements are based on a calibration curve from different Ba-O compounds. The effects of changes in oxidation number above and below the transition temperature and its role in high-T c superconductivity are discussed

  5. Far infrared spectroscopy of high-Tc superconductors at the National Synchrotron Light Source

    International Nuclear Information System (INIS)

    Perkowitz, S.; Williams, G.P.

    1989-01-01

    This paper reports the first far infrared transmission spectra for micron-thick films of high-T c rare-earth superconductors such as DyBaCuO, with implications for the superconducting gap. Spectra were obtained at Brookhaven's National Synchrotron Light Source, a new high-intensity, broad-band millimeter to infrared source. The National Synchrotron Light Source at Brookhaven National Laboratory, known for powerful X-ray and UV output, is also a high-intensity (10 to 1000 times above a black body), high-brightness (intensity per solid angle), broad-band, picosecond, millimeter to infrared source. These features make it valuable for far-infrared condensed matter experiments, especially those in highly absorbing or extremely small systems. A first application has been to measure very small infrared transmissions through thick bulk-like high-T c superconducting films. Preliminary measurements through films of the conventional superconductor Nb 3 Ge established techniques. These were followed by the first measurements (to the author's knowledge) through micron-thick films of high-T c rare-earth superconductors such as DyBaCuO over 10-300 cm -1 , which includes the superconducting gap according to BCS or moderately strong-coupled theory. The authors discuss the transmission evidence bearing on the existence of a gap and other important features of high-T c superconductors, and describe the synchrotron and instrumentation features which make possible these unusual measurements

  6. ALTERNATIVE MATERIALS FOR RAMP-EDGE SNS JUNCTIONS

    International Nuclear Information System (INIS)

    Jia, Q.; Fan, Y.; Gim, Y.

    1999-01-01

    We report on the processing optimization and fabrication of ramp-edge high-temperature superconducting junctions by using alternative materials for both superconductor electrodes and normal-metal barrier. By using Ag-doped YBa 2 Cu 3 O 7-x (Ag:YBCO) as electrodes and a cation-modified compound of (Pr y Gd 0.6-y )Ca 0.4 Ba 1.6 La 0.4 Cu 3 O 7 (y = 0.4, 0.5, and 0.6) as a normal-metal barrier, high-temperature superconducting Josephson junctions have been fabricated in a ramp-edge superconductor/normal-metal/superconductor (SNS) configuration. By using Ag:YBCO as electrodes, we have found that the processing controllability /reproducibility and the stability of the SNS junctions are improved substantially. The junctions fabricated with these alternative materials show well-defined RSJ-like current vs voltage characteristics at liquid nitrogen temperature

  7. Growth temperature dependence of flux pinning properties in ErBa2Cu3Oy thin films with nano-rods

    International Nuclear Information System (INIS)

    Haruta, M.; Sueyoshi, T.; Fujiyoshi, T.; Mukaida, M.; Kai, H.; Matsumoto, K.; Mele, P.; Maeda, T.; Horii, S.

    2011-01-01

    Nano-rods were introduced into ErBa 2 Cu 3 O y thin films to improve J c . Pinning properties depended on the growth temperature of the films. Morphology of nano-rods was affected by the growth temperature. The growth temperature is important to achieve high in-field J c 's. Irreversibility lines and distributions of local critical current density (J cl ) based on the percolation transition model were affected by the growth temperature (T s ) in 3.5 wt.%-BaNb 2 O 6 -doped ErBa 2 Cu 3 O y thin films. The vortex-Bose-glass-like state appeared by the introduction of nano-rods, and this vortex state was affected by T s . The shape and width of the J cl distribution strongly depended on T s . These results are probably caused by variations of the density and the growth direction for nano-rods reflecting T s . The growth temperature is an important factor to achieve higher critical current properties under magnetic fields for coated conductors of rare-earth-based cuprates with nano-rods.

  8. Producción y caracterización de la perovskita NdBa2SbO6 como sustrato para una película superconductora de YBa2Cu3O(7-δ

    Directory of Open Access Journals (Sweden)

    Queeny Madueño Pinto

    2002-07-01

    Full Text Available Las propiedades de las películas superconductores de alta temperatura crítica son dependientes de parámetros cristalográficos y de la estabilidad química entre sustrato y película. Por lo tanto, con el fin de producir una perovskita cúbica compleja policristalina de NdBa2SbO6, en forma de pastilla, por medio de la técnica de reacción de estado sólido. Este material no conductor fue mezclado con el policristal superconductor YBa2CuO(7-δ en proporciones volumétricas. Se encontró un buen acoplamiento de los parámetros de red a través de la técnica experimental de difracción de rayos X. La influencia de los porcentajes de volumen del NdBa2SbO6 sobre las propiedades superconductoras del YBa2CuO(7-δ fue estudiada a través de las medidas de magnetización dc. Los resultados obtenidos muestran que el material NdBa2SbO6 es un excelente candidato a sustrato para crecer películas superconductoras de YBa2CuO(7-δ.

  9. O vacancy formation in (Pr/Gd)BaCo2O5.5 and the role of antisite defects

    KAUST Repository

    Omotayo Akande, Salawu; Chroneos, Alexander; Schwingenschlö gl, Udo

    2017-01-01

    that O vacancy formation is significantly easier in PrBaCo2O5.5 than in GdBaCo2O5.5, the difference in formation energy being hardly modified by antisite defects. While pyramidally coordinated Co atoms are not affected, we show that the presence

  10. Positron annihilation study of the high-Tc (Bi, Pb)2Sr2Ca2Cu3Ox superconductor

    International Nuclear Information System (INIS)

    Lim, H.J.; Byrne, J.G.

    1997-01-01

    Positron lifetime spectroscopy (PLS) and positron Doppler-broadening spectroscopy (PDBS) were applied to the high-T c lead-doped Bi 2 Sr 2 Ca 2 Cu 3 O x (BPSCCO 2223) superconductor as a function of temperature. Neither positron lifetimes nor Doppler parameters (S, W, and S/W) showed significant change through T c . This may result from having the highest positron density in the open BiO 2 double layers and no significant positron density in the superconducting CuO 2 layers where positrons, if mainly present, are known to be sensitive to the transition in other high-T c superconductors. Doppler parameters showed that the probability of positron annihilations with core electrons in the lattice slightly increased and that the probability of positron annihilations with conduction electrons slightly decreased as temperature decreased from ambient temperature to 20 K. The lifetime associated with positron annihilations in the perfect lattice of the sample (τ 1 ) was 209 ps and, due to the annihilations at internal surfaces or voids in the sample (τ 2 ) was about 540 ps, independent of temperature. Finally, the mean lifetime for BSCCO 2223 was about 307 ps. (orig.)

  11. Determination of oxygen content in high Tc superconductors by deuteron particle activation analysis

    International Nuclear Information System (INIS)

    Tao Zhenlan; Yao, Y.D.; Kao, Y.H.

    1993-01-01

    The experimental method for determining the oxygen content in high T c superconductors is described in detail. This method is applied to determination of oxygen content in high T c Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O samples in which the stoichiometry is varied by reducing the copper and bismuth concentrations. The oxygen concentration is found to vary linearly with Cu(x = 0-0.2) and Bi (x = 0-0.4) deficiencies in YBa 2 Cu 3(1-x )O y and Bi 2(1-x) Sr 2 CaCu 2 O y respectively. X-ray powder diffraction measurements show that the compound of YBa 2 Cu 3(1-x) O y is orthorhombic in the variation range of x = 0-0.2

  12. High-density Bi-Pb-Sr-Ca-Cu-O superconductor prepared by rapid thermal melt processing

    Science.gov (United States)

    Moon, B. M.; Lalevic, B.; Kear, B. H.; McCandlish, L. E.; Safari, A.; Meskoob, M.

    1989-10-01

    A high quality, dense Bi-Pb-Sr-Ca-Cu-O superconductor has been successfully synthesized by rapid thermal melt processing. Conventionally sintered pellets were melted at 1200 °C, cooled rapidly, and then annealed. As-melted samples exhibited semiconductor behavior, which upon annealing became superconducting at 115 K [Tc(zero)=105 K]. A detailed study of various processing techniques has been carried out.

  13. Local valence balance in the structure of a high-temperature superconductor

    International Nuclear Information System (INIS)

    Nalbandyan, V.B.

    1990-01-01

    Hitherto superconductivity of complex oxides has been observed only if the metal is present in a mixed (nonintegral) degree of oxidation. It is of interest to verify the statement that in YBa 2 Cu 3 O x there is no copper in a degree of oxidation above 2+; instead of this, part of the oxygen is in the degree of oxidation 1-. Thus, the calculations of the valence forces tell against the presence of copper in a mixed degree of oxidation between 2+ and 3+ in high-temperature superconductors of the stoichiometric composition RBa 2 Cu 3 O 7 . In two-dimensional layers, copper is in the degree of oxidation 2+ (or even lower), while the electron holes are concentrated in one-dimensional chains - either in the form Cu(3+) or in the form O(1-)

  14. Study of critical current density from ac susceptibility measurements in (La1-xYx)2Ba2CaCu5O2 superconductors

    International Nuclear Information System (INIS)

    Nayak, P.K.; Ravi, S. . sravi@iitg.ernet.in

    2008-01-01

    We have prepared a series of compounds (La 1-x Y x ) 2 Ba 2 CaCu 5 O 2 for x = 0 to 0.5 by adding a CaCuO 2 layer to the parent compound La 2 Ba 2 Cu 4 O 2 and by doping Y in place of La. These materials are also prepared by adding 5 wt% of Ag to enhance the intergranular coupling and critical current density. X-ray diffraction measurements show that all the samples are essentially in single phase form and the patterns could be refined using P4/mmm space group in tetragonal cell. The typical lattice parameters are found to be a = b 3.856 A, c = 11.576 A for x = 0.5 sample. Temperature variations of dc electrical resistivity measured on the above samples show that they exhibit superconductivity with T c ranging from 60 to 75 K. Temperature and ac field amplitude variation of ac susceptibility have been measured on the above samples. The field variation of ac susceptibility data has been analyzed by using Bean critical state model. Using both temperature and field variations of ac susceptibility data, the material dependent parameters, such as critical current density as a function of temperature and effective volume fraction grains have been estimated. The Ag doped samples show relatively large critical current density compared to pure samples due to improved intergranular coupling. (author)

  15. Investigations on the local structures of Cu2+ at various BaO concentrations in 59B2O3-10K2O-(30-x)ZnO-xBaO-1CuO glasses

    Science.gov (United States)

    Jin, Jia-Rui; Wu, Shao-Yi; Hong, Jian; Liu, Shi-Nan; Song, Min-Xian; Teng, Bao-Hua; Wu, Ming-He

    2017-11-01

    The local structures and electron paramagnetic resonance (EPR) parameters for Cu2+ in 59B2O3-10K2O-(30-x)ZnO-xBaO-1CuO (BKZBC) glasses are theoretically investigated with distinct modifier BaO concentrations x (= 0, 6, 12, 18, 24 and 30 mol %). The ? clusters are found to undergo the relative tetragonal elongations of about 13.5 and 5.0% at zero and higher BaO concentrations. The concentration dependences of the measured d-d transition bands, g factors and A// are suitably reproduced from the Fourier type functions or sign functions of the relevant quantities with x by using only six adjustable parameters. The features of the EPR parameters and the local structures of Cu2+ are analysed in a consistent way by considering the differences in the local ligand field strength and electronic cloud admixtures around Cu2+ under addition of Ba2+ with the highest ionicity and polarisability. The present theoretical studies would be helpful to the researches on the structures, optical and EPR properties for the similar potassium barium zinc borate glasses containing copper with variation concentration of modifier BaO.

  16. Effect of light rare earth doping in 123 high temperature supercoductors

    Directory of Open Access Journals (Sweden)

    M. Mirzadeh

    2006-09-01

    Full Text Available   We have studied the structural and electrical properties of Gd(Ba2-xLaxCu3O7+δ [Gd(BaLa123], Gd(Ba2-xNdxCu3O7+δ [Gd(BaNd123], and Nd(Ba2-xPrxCu3O7+δ [Nd(BaPr123] compounds with 0.0≤x≤0.8 prepared by the standard solid-state reaction. The XRD patterns show that all of the samples with x≤0.5 are isosructure 123 phase, but in Gd(BaNd123 and Nd(BaPr123 there are several impurity peaks in the XRD patterns for x≥0.6. We estimated the xcsolubility=1.1, 0.6 and 0.55 in Gd(BaLa123, Nd(BaPr123, and Gd(BaNd123, respectively. The resistivity increases with the increase of doping. The decrease of Tc with the increase of Pr doping is faster than Nd and La doping. The normal-state resistivity is fitted for two and three dimensional variable range hopping (2D&amp3D-VRH and Coulomb gap (CG regimes, separately. Our results indicate that the dominant mechanism for x≥xcSIT is 3D-VRH. The broadening of magnetoresistance have been investigated by TAFC and AH models. The pinning energy and Josephson coupling energy, decrease with the increase of applied magnetic field as U~H-β, these values also decrease with doping concentration Pr is more effective than Nd and La.

  17. Superconducting thin films of YBa2Cu3O7-x

    International Nuclear Information System (INIS)

    Hudner, J.

    1993-01-01

    Thin films of the high temperature superconductor YBa 2 Cu 3 O 7-x (YBCO) are of significance in fundamental studies of oxide superconductors and for prospected electronic applications based on superconductors operating at liquid nitrogen temperatures (T= 77 K). Synthesis of YBCO thin films is complex and a large part of this thesis has been devoted to the elaboration of various techniques in forming YBCO thin films. A general observation was that synthesis of YBCO films exhibiting high zero-resistivity temperatures temperatures (T c ) ≥ 88 K and elevated critical current densities (J c ) ≥ 10 6 A/cm 2 at 77 K was possible under widely different conditions of film growth. For the BaF 2 -based method, various substrate materials were investigated. Among perovskite related substrates with low losses in the high frequency regime, LaA10 3 was found to yield YBCO films exhibiting the highest quality electrical properties. A study of YBCO film interaction with sapphire substrates was performed. It was suggested that the YBCO film on sapphire consists of weakly coupled superconducting grains. Compositional effects of Y, BA and Cu for MOCVD-YBCO films were examined with respect to morphology, structure, resistivity, as susceptibility and J c (T). High T c :s and J c :s were observed for an anomalous large compositional range of Cu in off-compositional YBCO films. This was shown to be related to the formation of Cu-rich precipitates embedded within a c-Axis oriented stoichiometric YBCO film matrix. Thermal critical current behavior at zero field in thin films of YBCO fabricated by various methods has been studied by three techniques: transport measurements on patterned microbridges, dc magnetization hysteresis loops using the Bean model and non-linear ac susceptibility analysis. Absolute critical current values obtained form the two former techniques when measured on the same YBCO film were observed to differ about a factor of two. The feasibility of non-linear ac

  18. Manifestation of vortex depinning transition in nonlinear current-voltage characteristics of polycrystalline superconductor Y1-xPrxBa2Cu3O7-δ

    International Nuclear Information System (INIS)

    Rivera, V.A.G.; Stari, C.; Sergeenkov, S.; Marega, E.; Araujo-Moreira, F.M.

    2008-01-01

    We present our recent results on the temperature dependence of current-voltage characteristics for polycrystalline Y 1-x Pr x Ba 2 Cu 3 O 7-δ superconductors with x=0.0, 0.1 and 0.3. The experimental results are found to be reasonably well fitted for all samples by a power like law of the form V=R(I-I c ) a(T) . Here, we assume that a(T)=1+Φ 0 I C (T)/2πk B T and I C (T)=I C (0)(1-T/T C ) 3/2 for the temperature dependences of the power exponent and critical current, respectively. According to the theoretical interpretation of the obtained results, nonlinear deviation of our current-voltage characteristics curves from Ohmic behavior (with a(T C )=1) below T C is attributed to the manifestation of dissipation processes. They have a characteristic temperature T p defined via the power exponent as a(T p )=2 and are related to the current induced depinning of Abrikosov vortices. Both T C (x) and T p (x) are found to decrease with an increase of Pr concentration x reflecting deterioration of the superconducting properties of the doped samples

  19. Synthesis, structural and physico-chemical studies of the monocrystal superconductor oxides Hg Ba{sub 2} Ca{sub n-1} Cu{sub n} O{sub 2n+2+{delta}}; Synthese, etudes structurales et physico-chimiques de monocristaux d`oxydes supraconducteurs Hg Ba{sub 2} Ca{sub n-1} Cu{sub n} O{sub 2n+2+{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Viallet-Guillen, Virginie [Dept. de Recherche sur l` Etat Condense, CEA Centre d` Etudes de Saclay, 91 - Gif-sur-Yvette (France)

    1998-01-01

    The thesis presents the synthesis and the structural and physico-chemical properties of the mercury-based monocrystal superconductor oxides. The results reported in the first chapter refer to the first three members of the mercury cuprate series Hg-1201, Hg-1212 and Hg-1223. In the second chapter detailed results concerning the structure of these compounds are given highlighting the features common to all cuprates and pointing out the peculiarities of mercury phases. The third chapter presents the phase diagrams ({delta}, T, p(O{sub 2})) of the compounds HgBa{sub 2}CuO{sub 4+{delta}} and HgBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub 8+{delta}} obtained by thermogravimetry under controlled atmosphere between 150 deg.C and 500 deg.C and thermodynamic equilibrium conditions. In the case of Hg-1201, the critical temperature shows a variation close to a parabolic law, with an optimal Tc of 96 K ({delta}{approx_equal}0.10) while in Hg-1223 the Tc increases linearly with the O content up to the optimal Tc of 135 K ({delta}{approx_equal}0.19) and decreases only by 2 K in the over-doped regime. Finally, in the fourth chapter different physical properties are reviewed. The obtained monocrystals allowed studying the resistive transitory anisotropy, the torque, the specific heat, the nuclear magnetic resonance and the Raman diffusion 212 refs., 106 figs., 30 tabs.

  20. Applied strain dependence of critical current and internal lattice strain for BaHfO_3-doped GdBa_2Cu_3O_y coated conductors

    International Nuclear Information System (INIS)

    Usami, Takashi; Yoshida, Yutaka; Ichino, Yusuke; Sugano, Michinaka; Machiya, Shutaro; Ibi, Akira; Izumi, Teruo

    2016-01-01

    The strain effect of REBa_2Cu_3O_y (REBCO: RE = Y, Gd, Sm)-coated conductors (CCs) on critical current (I_c) is one of the most fundamental factors for superconducting coil applications. In this study, we aim to clarify the effect of artificial pinning center shapes on the strain effect in BHO-doped GdBCO CCs. To achieve this, we fabricated a Pure-GdBCO CC, a BHO nanorod-doped GdBCO CC and a multilayered-GdBCO (ML-GdBCO) CC, and carried out bending tests. As the result, the strain dependence of I_c for each CC showed an upward convex and the peak strain of the BHO-doped GdBCO CC shifts towards the compressive strain independent of the BHO shapes. In addition, the strain sensitivity of I_c in the GdBCO CCs including BHO becomes smaller. To clarify the difference between the strain sensitivity of I_c and the peak strain among the CCs, we evaluated the residual strain and the slopes of the internal lattice strains against the applied tensile strain (β). From this measurement, the residual strains for the Pure-GdBCO CC and the ML-GdBCO CC were almost the same. In addition, there was no change in the β value between the Pure-GdBCO and ML-GdBCO CCs. These results suggest that the changes in peak strain and strain sensitivity were not related to the internal lattice strain. (author)

  1. Annealing experiments on and high-temperature behavior of the superconductor yttrium barium copper oxide (YBa2Cu3Ox)

    NARCIS (Netherlands)

    Brabers, V.A.M.; Jonge, de W.J.M.; Bosch, L.A.; Steen, van der C.; de Groote, A.M.W.; Verheyen, A.A.; Vennix, C.W.H.M.

    1988-01-01

    The high temperature behaviour (300–1100 K) of the superconductor YBa2Cu3Ox has been studied by annealing experiments, thermal dilatation, thermogravimetry and measurements of the electrical resistance and thermoelectric power. For the fast oxidation process of this compound, reaction enthalpies

  2. Operation of a 400MHz NMR magnet using a (RE:Rare Earth)Ba2Cu3O7-x high-temperature superconducting coil: Towards an ultra-compact super-high field NMR spectrometer operated beyond 1GHz.

    Science.gov (United States)

    Yanagisawa, Y; Piao, R; Iguchi, S; Nakagome, H; Takao, T; Kominato, K; Hamada, M; Matsumoto, S; Suematsu, H; Jin, X; Takahashi, M; Yamazaki, T; Maeda, H

    2014-12-01

    High-temperature superconductors (HTS) are the key technology to achieve super-high magnetic field nuclear magnetic resonance (NMR) spectrometers with an operating frequency far beyond 1GHz (23.5T). (RE)Ba 2 Cu 3 O 7- x (REBCO, RE: rare earth) conductors have an advantage over Bi 2 Sr 2 Ca 2 Cu 3 O 10- x (Bi-2223) and Bi 2 Sr 2 CaCu 2 O 8- x (Bi-2212) conductors in that they have very high tensile strengths and tolerate strong electromagnetic hoop stress, thereby having the potential to act as an ultra-compact super-high field NMR magnet. As a first step, we developed the world's first NMR magnet comprising an inner REBCO coil and outer low-temperature superconducting (LTS) coils. The magnet was successfully charged without degradation and mainly operated at 400MHz (9.39T). Technical problems for the NMR magnet due to screening current in the REBCO coil were clarified and solved as follows: (i) A remarkable temporal drift of the central magnetic field was suppressed by a current sweep reversal method utilizing ∼10% of the peak current. (ii) A Z2 field error harmonic of the main coil cannot be compensated by an outer correction coil and therefore an additional ferromagnetic shim was used. (iii) Large tesseral harmonics emerged that could not be corrected by cryoshim coils. Due to those harmonics, the resolution and sensitivity of NMR spectra are ten-fold lower than those for a conventional LTS NMR magnet. As a result, a HSQC spectrum could be achieved for a protein sample, while a NOESY spectrum could not be obtained. An ultra-compact 1.2GHz NMR magnet could be realized if we effectively take advantage of REBCO conductors, although this will require further research to suppress the effect of the screening current. Copyright © 2014 Elsevier Inc. All rights reserved.

  3. Experiments on the rf surface resistance of the perovskite superconductors at 3 GHz

    International Nuclear Information System (INIS)

    Hein, M.; Klein, N.; Mueller, G.; Piel, H.; Roeth, R.W.

    1988-01-01

    Since the discovery of the perovskite superconductors many experiments to explore their physical properties have been performed and various potential applications have been considered. The high critical temperature of more than 90 K obtained with Y 1 Ba 2 Cu 3 O/sub 7-δ/ (Y may be substituted by other rare earth elements) makes these superconductors interesting for applications in microwave technology. This has focused the authors interest on the investigation of their rf properties. Due to the sensitivity of the rf surface resistance to surface impurities and remaining non superconducting phases rf measurements are a good means to provide useful information about the quality of sample preparation and about physical properties of the superconductor itself. This contribution reports on the experimental determination of the rf surface resistance of Y 1 Ba 2 Cu 3 O/sub 7-δ/ and Eu 1 Ba 2 Cu 3 O/sub 7-δ/ in the normal and superconducting state at 3 GHz. In the first chapter the preparation of the ceramic samples and initial dc experiments are described. The main part of the paper describes the rf measurements which are performed in a superconducting niobium host cavity. The obtained results for both the surface resistance and the high field performance are discussed with respect to the preparation of the samples and regarding possible applications. 7 references, 7 figures, 2 tables

  4. Structure and properties of (Sr, Ca)CuO2-BaCuO2 superlattices grown by pulsed laser interval deposition

    NARCIS (Netherlands)

    Koster, Gertjan; Verbist, Karen; Rijnders, Augustinus J.H.M.; Rogalla, Horst; van Tendeloo, Gustaav; Blank, David H.A.

    2001-01-01

    We report on the preparation of CuBa2(SrxCa1¿x)nCun¿1Oy compounds by fabrication of (Ba,Sr,Ca)CuO2 superlattices with pulsed laser deposition (PLD). A technique called interval deposition is used to suppress multi-level or island growth resulting in high-quality superlattice structures. Both, the

  5. Electron-$\\gamma$ - perturbed angular correlation studies on high-T$_{C}$ superconductors

    CERN Document Server

    Correia, J G; Marques, J G; Ramos, A R; Lourenço, A A; Amaral, V S; Galindo, V; Senateur, J P; Weiss, F; Wahl, U; Melo, A A; Soares, J C; Sousa, J B

    2000-01-01

    Recent results on the study of high-T$_{c}$ superconductors using the e$^-\\!-\\gamma$ perturbed angular correlation technique are presented. The basic features of the experimental equipment and its installation at the ISOLDE facility are briefly described. Results obtained from $^{197m}$Hg implanted into high quality Y$_{1}$Ba$_{2}$Cu$_{3}$O$_{6+\\delta}$ epitaxy thin films are presented and discussed.

  6. Study of LnBaCo{sub 2}O{sub 6-d}elta (Ln = Pr, Nd, Sm and Gd) double perovskites as new cathode material for IT-SOFC

    Energy Technology Data Exchange (ETDEWEB)

    Chavez, E; Mueller, M; Mogni, L; Caneiro, A, E-mail: mogni@cab.cnea.gov.a [Centro Atomico Bariloche-CNEA, Instituto Balseiro. Av. Bustillo 9500, S. C. de Bariloche 8400 (Argentina)

    2009-05-01

    Oxides with double perovskites structures of general composition LnBaCo{sub 2}O{sub 6-d}elta (Ln = Pr, Nd, Sm and Gd) were synthesized by solid state reaction with the purpose to evaluate new materials to be used as cathodes in intermediate temperature solid oxide fuel cell (IT-SOFC). A preliminary study about electrochemical properties was performed by impedance spectroscopy between 500 and 800 deg. C under atmosphere of pure O{sub 2}. Symmetrical cells were obtained by spray deposition of LnBaCo{sub 2}O{sub 6-d}elta (Ln = Pr, Nd, Sm and Gd) at both sides of a dense ceramic electrolyte. The impedance spectroscopy measurements as a function of temperatures show a hysteresis loop which could be associated to a tetragonal/orthorhombic phase transition. The existence of this transition was corroborated by high temperature X-Ray diffraction and Differential Scanning Calorimetry measurements.

  7. Critical current density in (YBa2Cu3O7−δ)1−x–(PrBa2Cu3O7−δ)x melt-textured composites  

    DEFF Research Database (Denmark)

    Opata, Yuri Aparecido; Monteiro, João Frederico Haas Leandro; Jurelo, Alcione Roberto

    2018-01-01

    Melt textured (YBa2Cu3O7−δ)1−x–(PrBa2Cu3O7−δ)x composites (x = 0.00 and x = 0.05) were grown using the top seeding method. The effect of the PrBa2Cu3O7−δ phase on the growth process and the modification of the microstructure as well as on the physical properties was analyzed. X-ray analyses...... indicated that both pure and Pr-doped samples present an orthorhombic superconducting phase. From resistivity measurements for YBa2Cu3O7−δ and (YBa2Cu3O7−δ)0.95–(PrBa2Cu3O7−δ)0.05 samples, the Tcab did not change and was around 90.5 K. However, from magnetic measurements, the superconductivity was observed...... in critical temperatures TC = 92.9 K and 92.4 K for YBa2Cu3O7−δ and (YBa2Cu3O7−δ)0.95–(PrBa2Cu3O7−δ)0.05 samples, respectively. The YBa2Cu3O7−δ sample showed higher critical current densities than those shown by the (YBa2Cu3O7−δ)0.95–(PrBa2Cu3O7−δ)0.05 sample, with values of JC = 5.85 × 105 A/cm2 and 4...

  8. Positron annihilation study of the high-T{sub c} (Bi, Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Lim, H.J. [Utah Univ., Salt Lake City, UT (United States). Dept. of Metallurgical Engineering; Byrne, J.G. [Utah Univ., Salt Lake City, UT (United States). Dept. of Metallurgical Engineering

    1997-03-01

    Positron lifetime spectroscopy (PLS) and positron Doppler-broadening spectroscopy (PDBS) were applied to the high-T{sub c} lead-doped Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} (BPSCCO 2223) superconductor as a function of temperature. Neither positron lifetimes nor Doppler parameters (S, W, and S/W) showed significant change through T{sub c}. This may result from having the highest positron density in the open BiO{sub 2} double layers and no significant positron density in the superconducting CuO{sub 2} layers where positrons, if mainly present, are known to be sensitive to the transition in other high-T{sub c} superconductors. Doppler parameters showed that the probability of positron annihilations with core electrons in the lattice slightly increased and that the probability of positron annihilations with conduction electrons slightly decreased as temperature decreased from ambient temperature to 20 K. The lifetime associated with positron annihilations in the perfect lattice of the sample ({tau}{sub 1}) was 209 ps and, due to the annihilations at internal surfaces or voids in the sample ({tau}{sub 2}) was about 540 ps, independent of temperature. Finally, the mean lifetime for BSCCO 2223 was about 307 ps. (orig.).

  9. Observation of weakly adsorbed oxygen on Y5Ba6Cu11Oy

    International Nuclear Information System (INIS)

    Kao, Sendjaja; Ng, K.Y.S.

    1992-01-01

    In the Y-Ba-Cu-O compound, several investigators have observed superconductivity-like phenomena at higher temperatures, some even reaching zero resistance at 250 K. Huang et al. reported an observation of sharp resistivity drops, at least four orders of magnitude at ca. 230 K, in one annealed sample of Eu 1 Ba 2 Cu 3 O 6+x . But the resistance drop disappeared after thermal cycling, although the correlated magnetic anomalies observed in their magnetic measurements persisted for many thermal cycles. Recently, Chen et al reported that the superconductivity-like transition at a temperature above 200 K in their mixed-phase YBaCuO persisted for 29 thermal cycles. The samples were treated by a low-temperature (50-70C) oxygenation process and enclosed in oxygen environment during electrical and magnetic measurements. They also found that this higher-temperature transition could not survive thermal cycling when the sample was in helium atmosphere. The role oxygen plays in their observations is not clear, but they speculated that weakly bonded oxygen atom/atoms are responsible for the high-temperature phase. This observation of T c > 200 K in oxygen environment is recently confirmed by Schonberger et al. in highly oriented multiphase Y-Ba-Cu-O thin film. Here, the authors observed, for the first time, adsorption of weakly bonded oxygen at low temperature (≤250C) by a Y 5 Ba 6 Cu 11 O y sample, using thermogravimetric analysis. The resulting oxygen enriched phase in the surface layers may be attributed to the observation of a superconductivity-like transition at above 200 K

  10. Superconductivity and spin gap in the zigzag-chain t-J model simulating a CuO double chain in Pr2Ba4Cu7O15-δ

    International Nuclear Information System (INIS)

    Sano, Kazuhiro; Ono, Yoshiaki

    2007-01-01

    Using the numerical diagonalization method, we examine the one-dimensional t 1 -t 2 -J 1 -J 2 model (zigzag-chain t-J model) which is an effective model for metallic CuO double chains in the super-conductor Pr 2 Ba 4 Cu 7 O 15-δ . Based on the Tomonaga-Luttinger liquid theory, we calculate the Luttinger liquid parameter K ρ as a function of the electron density n. It is found that superconductivity is realized in the parameter region, which is in accordance with experimental results. We show the phase diagram of a spin gap in the t 2 /|t 1 |-n plane by analyzing the expectation value of the twist operator Z σ in the spin sector. The spin gap appears in the region with a large t 2 /|t 1 |, where the phase boundary at half filling is consistent with that of the known frustrated quantum spin system. The analysis also suggests that the estimated value of the spin gap reaches ∼100 K in the realistic parameter region of Pr 2 Ba 4 Cu 7 O 15-δ . (author)

  11. The relationship of structure to superconductivity in the Pr-Ba-Cu-O system

    Science.gov (United States)

    Minseo, P.

    1994-05-01

    The relation of structure to lack of superconductivity in Pr-Ba-Cu-O was systematically investigated. First, the phase equilibria of this system was studied to find the processing parameters which maximize the cation-site ordering between Pr and Ba ions. Second, a comparative study between superconducting Nd-Ba-Cu-O and nonsuperconducting Pr-Ba-Cu-O was performed by forming solid-solution Nd-Pr-Ba-Cu-O. The relation between structure and superconductivity in Nd(1-x)Pr(x)Ba2Cu3O(7-delta) is investigated. T sub c decreases monotonically with increasing x and superconductivity disappears at around x = 0.3 to 0.4. T sub c is enhanced by 10 K when the sample is processed at an oxygen partial pressure (PO2) of 0.01 atm, followed by oxygenation at 450 C. Depression of T sub c as a function of x and PO2 is explained in terms of a charge-transfer model. It is suggested that destruction of superconductivity in the RE(1-x)Pr(x)Ba2Cu3O(7-delta) (RE=rare-earth) system can be viewed as disruption of four-fold planar coordinated Cu ions in the chain-site due to permanent occupation of extra Pr ions on Ba sites.

  12. A determination of the oxygen non-stoichiometry of the oxygen storage materials LnBaMn2O5+δ (Ln=Gd, Pr)

    Science.gov (United States)

    Jeamjumnunja, Kannika; Gong, Wenquan; Makarenko, Tatyana; Jacobson, Allan J.

    2016-07-01

    The A-site ordered double-perovskite oxides, LnBaMn2O5+δ (Ln=Gd, Pr), were synthesized and investigated to understand the effect of A site cation substitution on the oxygen storage properties of these materials. The present results are compared with our previous data for YBaMn2O5+δ. The results clearly reveal that changing the Ln cation strongly influences the oxidation/reduction behavior of LnBaMn2O5+δ. Based on thermogravimetric analysis data, oxygen uptake begins at lower temperatures in both air and oxygen in compounds with Ln3+ ions larger than Y3+. These oxides exhibit almost complete and reversible oxygen uptake/release between fully-reduced LnBaMn2O5 and fully-oxidized LnBaMn2O6 during changes of the oxygen partial pressure between air and 1.99% H2/Ar. In addition, the oxygen non-stoichiometries of GdBaMn2O5+δ and PrBaMn2O5+δ were determined as a function of pO2 at 600, 650, 700 and 750 °C by Coulometric titration at near-equilibrium conditions. The results confirm that these materials have two distinct phases on oxidation/reduction with δ≈0, 0.5 and a third phase with a range of composition with an oxygen content (5+δ) approaching 6. The stabilities of the LnBaMn2O5+δ phases extend over a wide range of oxygen partial pressures (∼10-25≤pO2 (atm)≤∼1) depending on temperature. Isothermal experiments show that the larger the Ln3+ cation the lower pO2 for phase conversion. At some temperatures and pO2 conditions, the LnBaMn2O5+δ compounds are unstable with respect to decomposition to BaMnO3-δ and LnMnO3. This instability is more apparent in Coulometric titration experiments than in thermogravimetric analysis. The Coulometric titration experiments are necessarily slow in order to achieve equilibrium oxygen compositions.

  13. Dependence of Tc on the oxygen distribution in the Cu-O chains in the high temperature superconductors YBa2Cu3O6+x

    International Nuclear Information System (INIS)

    Uimin, G.V.; Gantmakher, V.F.; Neminsky, A.M.; Novomlinsky, L.A.; Shovkun, D.V.; Bruell, P.

    1992-01-01

    It is experimentally confirmed that in YBa 2 Cu 3 O 6+x ceramics with x fixed within the range 0.4-0.5 the temperature of the superconducting transition Tc can be appreciably reduced by quenching a sample from moderate temperatures between 50degC and 200degC. The theory developed for the description of the ensemble of Cu-O-... chain fragments in orthorhombic phase is applied for the explanation of the experimental results, which can be interpreted as follows. In ortho-II phase the oxygen filling factors in oxygen deficient Cu(1) planes alternate from row to row. Alternation decreases with temperature increasing. Redistribution of the oxygen ions between the rows increases the fraction of short Cu-O-... chain fragments which cannot inject holes into CuO 2 planes. This diminishes the hole concentration in the Cu(2) planes and, hence, Tc. Near 150degC the sample undergoes the second order transition into ortho-I phase where rows are equally filled with oxygen. Further increasing of the temperature does not reveal an appreciable reduction of Tc. A comparison of the experiment with the simplest model is performed. (orig.)

  14. Positron lifetime studies on the BiSrCaCuO(F) superconductors

    International Nuclear Information System (INIS)

    Shi Zhiqiang; Chao Xixu; Wu Lingyun

    1995-01-01

    We have measured the positron lifetime and the transition temperature T c as a function of doped F content for Bi 2 Sr 2 CaCu 2 O y-x F x superconductors. The observed results are interpreted in terms of the change of the electron density in the Bi - O layers, which is the region probed by the positron, and the hole concentration in the Cu - O planes, which is correlated with the T c of the sample. From this point of view, it is suggested that the F atom mainly substitutes the oxygen atom in the Bi - O layers, and it causes the electrons transfer from the Bi - O layers to the Sr - O planes; when x = 0.4, the F atom mainly substitues the oxygen atom in the Sr - O planes, it causes the electrons transfer from the Sr - O planes to the Bi - O layers and the Cu - O planes. (orig.)

  15. Vortex states of Tl2Ba2CuO6+δ studied via 205Tl NMR at 2 tesla

    International Nuclear Information System (INIS)

    Itoh, Yutaka; Michioka, Chishiro; Yoshimura, Kazuyoshi; Hayashi, Akihiko; Ueda, Yutaka

    2005-01-01

    We report a 205 Tl NMR study of vortex states in an aligned polycrystalline sample of an overdoped high-T c superconductor, Tl 2 Ba 2 CuO 6+δ (Tc - 85 K), at a magnetic field of 2 T along the c axis. We observed an imperfect vortex lattice, so-called Bragg glass, at T=5 K, the coexistence of vortex solid and vortex liquid between 10 and 60 K, and vortex melting between 65 and 85 K. No evidence for local antiferromagnetic ordering at vortex cores was found for our sample. (author)

  16. Positron-annihilation studies on the Bi-Sr-Ca-Cu-O superconductor

    International Nuclear Information System (INIS)

    Sundar, C.S.; Bharathi, A.; Ching, W.Y.; Jean, Y.C.; Hor, P.H.; Meng, R.L.; Huang, Z.J.; Chu, C.W.

    1991-01-01

    The results of positron-lifetime measurements as a function of temperature, across T c , and as a function of heat treatment are presented. The lifetime in Bi-Sr-Ca-Cu-O does not show any variation with temperature in the range of 10 to 300 K, a result that is in contrast with other cuprate superconductors. The absence of lifetime variation across T c is understood in terms of the calculated positron-density distribution, which indicates that the maximum of the positron density is in the region between the Bi-O layers with no significant density in the superconducting CuO 2 layers. Positron-lifetime measurements as a function of heat treatment indicate a decrease in lifetime as the annealing temperature is lowered from 800 degree C to 100 degree C. The decrease in lifetime, which is correlated with the increase in the weight of the sample, is explained in terms of the intercalation of the excess oxygen in the region between the Bi-O layers, which is the region probed by the positron

  17. Nanometre-sized inhomogeneity in high-Jc Bi2Sr2CaCu2O8+δ superconductors

    International Nuclear Information System (INIS)

    Nishiyama, M; Kinoda, G; Zhao, Y; Hasegawa, T; Itoh, Y; Koshizuka, N; Murakami, M

    2004-01-01

    We have performed atomic-scale high-resolution scanning tunnelling microscopy and spectroscopy measurements on the cleaved surface of single crystal Bi 2 Sr 2 CaCuO 8+δ superconductors with high critical current density J c . The samples exhibited rugged structure about 15 nm in period, larger than the modulation of the BiO layer, which corresponded well to the energy gap distribution at 77 K. The presence of inhomogeneity from a nanometre to a micrometre scale, in the energy gap distribution, the structural modulation and the chemical composition fluctuation, may play an important role in improving J c values in the Bi 2 Sr 2 CaCuO 8+δ crystals

  18. Microwave surface resistance of bulk YBa2Cu3O6+x material

    Science.gov (United States)

    Fathy, A.; Kalokitis, D.; Belohoubek, E.; Sundar, H. G. K.; Safari, A.

    1988-10-01

    Superconducting Y-Ba-Cu-O samples were prepared by conventional solid-state reaction. The microwave surface resistance of 1:2:3 compound superconductor material was measured in a special disk resonator structure at 10 GHz. At liquid-nitrogen temperatures the microwave surface resistance is comparable to that of Au. At lower temperature (~10 K) the surface resistance is an order of magnitude lower than that of Au at the same temperature.

  19. Formation of high-Tc YBa2Cu3O(7-delta) films on Y2BaCuO5 substrate

    Science.gov (United States)

    Wang, W. N.; Lu, H. B.; Lin, W. J.; Yao, P. C.; Hsu, H. E.

    1988-07-01

    High-Tc superconducting YBa2Cu3O(7-delta) films have been successfully prepared on green Y2BaCuO5 (2115) ceramic substrate. The films have been formed by RF sputtering and screen printing with post annealing at 925 C. Regarding superconducting features, the sharp resistivity drop with Tc onset around 95 K (midpoint 84 K) and 99 K (midpoint 89 K) has been observed for RF sputtered and printed films respectively. Both films show the excellent adhesion towards the 2115 substrate. Powder X-ray diffraction profiles indicate a majority of 1237 phase with preferred orientation for RF sputtered thin film.

  20. Perturbed angular correlations studies in the HgBa$_2$CaCu$_2$O$_{6+\\delta}$ high-T$_c$ superconductor

    CERN Document Server

    Mendonca, Tania Melo; Haas, Heinz; Odier, Philippe; Tavares, Pedro; SIlva, Manuel Ribeiro; Lopes, Armandina; Darie, Celine; Araujo, Joao Pedro

    2011-01-01

    The electric field gradients at $^{199m}$Hg nuclei have been measured via the perturbed angular correlation (PAC) technique, allowing a full characterization of the Hg neighborhood charge distribution at high oxygen doping on the Hg planes. The PAC technique has been applied to investigate the effect of high oxygen pressure during the measurement. Polycrystalline HgBa$_2$CaCu$_2$O$_{6+\\delta}$ (Hg-1212) samples have been annealed at 152 bar pressurized oxygen. The influence of oxygen pressure during the experiment was then investigated by measuring the samples at atmospheric pressure and under 152 bar oxygen pressure. The present set of PAC experiments shows that at high oxygen concentrations there is a non-uniform oxygen distribution. Moreover, the Hg environment is not free from oxygen and the results hint to a new type of ordering.

  1. Introduction of BaSnO3 and BaZrO3 artificial pinning centres into 2G HTS wires based on PLD-GdBCO films. Phase I of the industrial R&D programme at SuperOx

    Science.gov (United States)

    Chepikov, V.; Mineev, N.; Degtyarenko, P.; Lee, S.; Petrykin, V.; Ovcharov, A.; Vasiliev, A.; Kaul, A.; Amelichev, V.; Kamenev, A.; Molodyk, A.; Samoilenkov, S.

    2017-12-01

    An industrial R&D programme is ongoing at SuperOx, aimed at improving 2G HTS wire performance in magnetic field. We introduce perovskite artificial pinning centres (APC) into the HTS layer matrix. In contrast to most studies described in the literature, we use the high rate production processing parameters and PLD equipment at SuperOx. This paper reports the results of Phase I of this programme. We fabricated 2G HTS wires by pulsed laser deposition of GdBCO films doped with 6%, 12% and 18% (molar) of BaSnO3 and 6% (molar) of BaZrO3, and compared their performance with an undoped reference sample. The depositions were carried out at production growth rates of 375, 560 and 750 nm min-1 by varying laser pulse frequency. BaZrO3 and BaSnO3 formed columnar semi-coherent nanoinclusions in the GdBCO film matrix. The average transverse size of the nanocolumns was about 5 nm, and their volume density correlated with the dopant concentration. All doped samples exhibited much lower angular anisotropy of in-field critical current and higher lift-factors than the undoped sample. Samples containing 6% BaSnO3 and deposited at the lower growth rates, had higher I c than the undoped sample in the entire temperature range, in a wide range of magnetic field (B//c). The sample containing 6% BaZrO3 had higher I c than the undoped sample at 20 and 4.2 K. These results are an encouraging start of our programme, as they show a positive impact of APC introduced into 2G HTS wires fabricated at production throughput. Phase II work will be focussed on maximising the improvements in specific temperature and field conditions, as well as on the verification of reproducibility of the improvements in production wires.

  2. Studies of nonlinear electrodynamics of high-temperature superconductors

    International Nuclear Information System (INIS)

    Lam, Q.H.

    1991-01-01

    Nonlinear electrodynamics of high-Tc superconductors are studied theoretically and experimentally. For powdered samples, a novel model is presented in which the metallographically observed superconducting grains in the powder are modeled as superconducting current loops of various areas with weak links. Surprising harmonic generation behavior in an ac field, H 1 cos(ωt), is predicted by the model; the power at high harmonics show sharp dips almost periodic in a super-posing dc magnetic field, revealing flux quantization in the prototype loops in the model. Such oscillation of the harmonic power in dc magnetic field, P nf (H dc ), is experimentally observed in powdered YBa 2 Cu 3 O 7 . For bulk sintered cylindrical samples, a generalized critical state model is presented. The nonlinear electrodynamics are due to flux-pinning. Experiments in ac and dc magnetic fields on a sintered cylindrical rod of YBa 2 Cu 3 O 7 yield unambiguous evidence of independent inter- and intragranular contributions to the complex harmonic permeability μ n = μ' n - iμ double-prime n . These data, together with P nf (H dc ), are explained quantitatively by the generalized critical state model, yielding a dependence on magnetic field of J c (H) ∼ H 02 local for the intergranular component, a steeper field dependence than for conventional type-II superconductors. Temperature-dependence measurements reveal that, while the intragranular supercurrents disappear at T c ≥ 91.2 K, the intergranular supercurrents disappear at T ≥ 86.6 K

  3. Nanostructured LnBaCo2O6− (Ln = Sm, Gd with layered structure for intermediate temperature solid oxide fuel cell cathodes

    Directory of Open Access Journals (Sweden)

    Augusto E. Mejía Gómez

    2017-04-01

    Full Text Available In this work, we present the combination of two characteristics that are beneficial for solid oxide fuel cell (SOFC cathodic performance in one material. We developed and evaluated for the first time nanostructured layered perovskites of formulae LnBaCo2O6-d with Ln = Sm and Gd (SBCO and GBCO, respectively as SOFC cathodes, finding promising electrochemical properties in the intermediate temperature range. We obtained those nanostructures by using porous templates to confine the chemical reagents in regions of 200-800 nm. The performance of nanostructured SBCO and GBCO cathodes was analyzed by electrochemical impedance spectroscopy technique under different operating conditions using Gd2O3-doped CeO2 as electrolyte. We found that SBCO cathodes displayed lower area-specific resistance than GBCO ones, because bulk diffusion of oxide ions is enhanced in the former. We also found that cathodes synthesized using smaller template pores exhibited better performance.

  4. Directly coupled direct current superconducting quantum interference device magnetometers based on ramp-edge Ag:YBa2Cu3O7-x/PrBa2Cu3O7-x/Ag:YBa2Cu3O7-x junctions

    International Nuclear Information System (INIS)

    Jia, Q.X.; Yan, F.; Mombourquette, C.; Reagor, D.

    1998-01-01

    Directly coupled dc superconducting quantum interference device (SQUID) magnetometers on LaAlO 3 substrates were fabricated using ramp-edge superconductor/normal-metal/superconductor junctions, where Ag-doped YBa 2 Cu 3 O 7-x was used for the electrode and PrBa 2 Cu 3 O 7-x for the normal-metal barrier. A flux noise of 8x10 -6 Φ 0 Hz -1/2 at 10 kHz measured with a dc bias current was achieved at 75 K, which corresponded to a field sensitivity of 400fTHz -1/2 for a magnetometer with a pick-up loop area of 8.5mmx7.5mm. Most significantly, the noise floor increased at lower frequencies with a frequency dependence slightly less than 1/f. The field noise of the SQUID magnetometers increased by only 25% after cycling the devices from zero field to 500 mG. In a static earth close-quote s magnetic field background, the field noise of the SQUID magnetometers increased by less than a factor of 2. copyright 1998 American Institute of Physics

  5. Electronic Structure of the Bismuth Family of High Temperature Superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Dunn, Lisa

    2002-03-07

    large superconducting phase transition temperature in a high temperature superconductor is associated with parameters that cause both large pairing strength and strong phase coherence in the system. The number of CuO2 layers in each unit cell is just one of the factors that affect these parameters.

  6. Synthesis, structural and physico-chemical studies of the monocrystal superconductor oxides Hg Ba2 Can-1 Cun O2n+2+δ

    International Nuclear Information System (INIS)

    Viallet-Guillen, Virginie

    1998-01-01

    The thesis presents the synthesis and the structural and physico-chemical properties of the mercury-based monocrystal superconductor oxides. The results reported in the first chapter refer to the first three members of the mercury cuprate series Hg-1201, Hg-1212 and Hg-1223. In the second chapter detailed results concerning the structure of these compounds are given highlighting the features common to all cuprates and pointing out the peculiarities of mercury phases. The third chapter presents the phase diagrams (δ, T, p(O 2 )) of the compounds HgBa 2 CuO 4+δ and HgBa 2 Ca 2 Cu 3 O 8+δ obtained by thermogravimetry under controlled atmosphere between 150 deg.C and 500 deg.C and thermodynamic equilibrium conditions. In the case of Hg-1201, the critical temperature shows a variation close to a parabolic law, with an optimal Tc of 96 K (δ≅0.10) while in Hg-1223 the Tc increases linearly with the O content up to the optimal Tc of 135 K (δ≅0.19) and decreases only by 2 K in the over-doped regime. Finally, in the fourth chapter different physical properties are reviewed. The obtained monocrystals allowed studying the resistive transitory anisotropy, the torque, the specific heat, the nuclear magnetic resonance and the Raman diffusion

  7. Structural instability of Y1-xPrxBa2Cu3O7-δ superconductors studied by positron annihilation lifetime

    International Nuclear Information System (INIS)

    Gou Zhenhui; Chen Feng; Zheng Shengnan; Zhao Zhongxian; Zhu Shengyun

    1995-01-01

    The temperature dependence of the positron annihilation lifetime in high-quality, single-phase Y 1-x Pr x Ba 2 Cu 3 O 7-δ has been measured from 78 to 300K for a better understanding of the origin of the normal state anomaly observed in high T c superconductivity studies. The normal state anomaly has been detected around 30 to 40K above T c for the samples with x=0.0 and 0.1, but, it was not found for the sample with x=0.2 where T c is lower than 80K. The experimental results show that the phase transition-like behavior caused by the structural instability results in the normal state anomaly which acts as a the precursor of high T c superconductivity. (orig.)

  8. Melt spin processing and recrystallization of REBa2Cu3O7-x

    International Nuclear Information System (INIS)

    Folkerts, T.J.; Kramer, M.J.; Dennis, K.W.; McCallum, R.W.

    1992-01-01

    This paper introduces a containerless melt-spin processing technique for REBa 2 Cu 3 O 7-x using pre-reacted oxide powders which are rapidly melted and subsequentially quenched in a controlled atmosphere. This results in flakes with typical dimensional of 3000 x 150 x 15μm 3 . Gd123 and Nd123 form nearly amorphous ribbons with only minor BaCu 2 O 2 when dropped in N 2 . Y123 contains Y 2 O 3 , but that the Ba-Cu-P phases present depend on the processing parameters. SEM and TEM studies show these phases are finely diapered; the typical grain size for Y 2 O 3 is 1-2μm, and for the Ba-Cu-O phases it is <0.5μm. Upon recrystallization from the amorphous ribbon, the Gd123 and Nd123 form field directly into the 123 phase while the recrystallization of the Y123 ribbons is less direct

  9. Effect of template post-annealing on Y(Dy)BaCuO nucleation on CeO2 buffered metallic tapes

    Science.gov (United States)

    Hu, Xuefeng; Zhong, Yun; Zhong, Huaxiao; Fan, Feng; Sang, Lina; Li, Mengyao; Fang, Qiang; Zheng, Jiahui; Song, Haoyu; Lu, Yuming; Liu, Zhiyong; Bai, Chuanyi; Guo, Yanqun; Cai, Chuanbing

    2017-08-01

    Substrate engineering is very significant in the synthesis of the high-temperature superconductor (HTS) coated conductor. Here we design and synthesize several distinct and stable Cerium oxide (CeO2) surface reconstructions which are used to grow epitaxial films of the HTS YBa2Cu3O7-δ (YBCO). To identify the influence of annealing and post-annealing surroundings on the nature of nucleation centers, including Ar/5%H2, humid Ar/5%H2 and O2 in high temperature annealing process, we study the well-controlled structure, surface morphology, crystal constants and surface redox processes of the ceria buffers by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and field-emission scanning electronic microscopy (FE-SEM), respectively. The ceria film post-annealed under humid Ar/5%H2 gas shows the best buffer layer properties. Furthermore, the film absorbs more oxygen ions, which appears to contribute to oxygenation of superconductor film. The film is well-suited for ceria model studies as well as a perfect substitute for CeO2 bulk material.

  10. Evolution of the specific-heat anomaly of the high-temperature superconductor YBa2Cu3O7 under influence of doping through application of pressure up to 10 GPa

    OpenAIRE

    Lortz, Rolf; Junod, Alain; Jaccard, Didier; Wang, Yuxing; Meingast, Christoph; Masui, Takahiko; Tajima, Setsuko

    2005-01-01

    The evolution of the specific-heat anomaly in the overdoped range of a single crystal of the high-temperature superconductor YBa2Cu3O7 has been studied under influence of pressure up to 10 GPa, using AC calorimetry in a Bridgman-type pressure cell. We show that the specific-heat jump as well as the bulk Tc are reduced with increasing pressure in accordance with a simple charge-transfer model. This new method enables us through pressure-induced charge transfer to study the doping dependence of...

  11. Thermal contact conductance of metallic coated BiCaSrCuO superconductor/copper interfaces at cryogenic temperatures

    International Nuclear Information System (INIS)

    Ochterbeck, J.M.; Peterson, G.P.; Fletcher, L.S.

    1992-01-01

    The effects of vapor deposited coatings on the thermal contact conductance of cold pressed, normal state BiCaSrCuO superconductor/oxygen-free copper interfaces were experimentally investigated over a pressure range of 200 to 2,000 kPa. Using traditional vapor deposition processes, thin coatings of indium or lead were applied to the superconductor material to determine the effect on the heat transfer occurring at the interface. The test data indicate that the contact conductance can be enhanced using these coatings, with indium providing the greater enhancement. The experimental program revealed the need for a better understanding and control of the vapor deposition process when using soft metallic coatings. Also, the temperature-dependent microhardness of copper was experimentally determined and found to increase by approximately 35 percent as the temperature decreased from 300 to 85 K. An empirical model was developed to predict the effect of soft coatings on the thermal contact conductance of the superconductor/copper interfaces. When applied, the model agreed well with the data obtained in this investigation at low coating thicknesses but overpredicted the data as the thickness increased. In addition, the model agreed very well with data obtained in a previous investigation for silvercoated nickel substrates at all coating thicknesses

  12. Melt processed high-temperature superconductors

    CERN Document Server

    1993-01-01

    The achievement of large critical currents is critical to the applications of high-temperature superconductors. Recent developments have shown that melt processing is suitable for producing high J c oxide superconductors. Using magnetic forces between such high J c oxide superconductors and magnets, a person could be levitated.This book has grown largely out of research works on melt processing of high-temperature superconductors conducted at ISTEC Superconductivity Research Laboratory. The chapters build on melt processing, microstructural characterization, fundamentals of flux pinning, criti

  13. Electronic structures of PrBa2Cu3O7, Pr2Ba4Cu7O15-y(y=0,1), and PrBa2Cu4O8 based on LSDA+U method

    International Nuclear Information System (INIS)

    Tavana, A.; Shirazi, M.; Akhavan, M.

    2009-01-01

    The electronic structures of PrBa 2 Cu 3 O 7 (Pr123), Pr 2 Ba 4 Cu 7 O 15-y (Pr247), and PrBa 2 Cu 4 O 8 (Pr124) cuprates have been obtained using density-functional theory in the local spin density approximation plus onsite Coulomb interaction (LSDA+U). Onsite Hubbard correlation, U, has been considered for Pr-f and Cu-d orbitals and the effects of considering these correlation corrections on the Pr-O hybridizations have been inspected. Results imply that the Pr ionization state in Pr123 system is constituted from two different configurations, and the energy of the f states in these two configurations has an important role in superconductivity properties of the system. Our calculations also show that in both Pr124 and Pr247 systems, suppression of superconductivity is weaker than that in the Pr123 system. This occurs due to the weaker Pr-O bond in both Pr124 and Pr247 systems. The role of the double chain and single chain on the conduction properties of these compounds has been investigated. We have also studied the effect of oxygen deficiency in Pr247 system, which seems to revive superconductivity in this system. Investigating the hole carriers in the CuO 2 plane shows a correlation between superconductivity suppression and hole decrement in the planes. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  14. Synthesis of CuO nanoflower and its application as a H2O2 sensor

    Indian Academy of Sciences (India)

    Administrator

    CuO; nanoflowers; electrochemical; H2O2. 1. Introduction. Cupric oxide (CuO) is an important transition metal oxide ... several high temperature superconductors and giant mag- ... precipitate was washed with ethanol and distilled water.

  15. LaNiO3 buffer layers for high critical current density YBa2Cu3O7-δ and Tl2Ba2CaCu2O8-δ films

    International Nuclear Information System (INIS)

    Carlson, C.M.; Parilla, P.A.; Siegal, M.P.; Ginley, D.S.; Wang, Y.; Blaugher, R.D.; Price, J.C.; Overmyer, D.L.; Venturini, E.L.

    1999-01-01

    We demonstrate high critical current density superconducting films of YBa 2 Cu 3 O 7-δ (YBCO) and Tl 2 Ba 2 CaCu 2 O 8-δ (Tl-2212) using LaNiO 3 (LNO) buffer layers. YBCO films grown on an LNO buffer layer have only a slightly lower J c (5 K, H=0) than films grown directly on a bare LaAlO 3 substrate. YBCO films grown on LNO buffer layers exhibit minor microstructural disorder and enhanced flux pinning. LNO-buffered Tl-2212 samples show large reductions in J c at all temperatures and fields compared to those grown on bare LaAlO 3 , correlating to both a-axis grain and nonsuperconducting phase formation. LNO could be a promising buffer layer for both YBCO and Tl-based superconducting films in coated conductor applications. copyright 1999 American Institute of Physics

  16. LaNiO3 Buffer Layers for High Critical Current Density YBa2Cu3O7δ and Tl2Ba2CaCu2O8δ Films

    International Nuclear Information System (INIS)

    Carlson, C.M.; Parilla, P.A.; Siegal, M.P.; Ginley, D.S.; Wang, Y.-T.; Blaugher, R.D.; Price, J.C.; Overmyer, D.L.; Venturini, E.L.

    1999-01-01

    We demonstrate high critical current density superconducting films of YBa 2 Cu 3 O 7-δ (YBCO) and Tl 2 Ba 2 CaCu 2 O 8-δ (Tl-2212) using LaNiO 3 (LNO) buffer layers. YBCO films grown on an LNO buffer layer have only a slightly lower J c (5K, H=0) than films grown directly on a bare LaAlO 3 substrate. It is noteworthy that YBCO films grown on LNO buffer layers exhibit minor microstructural disorder and enhanced flux pinning. LNO-buffered Tl-2212 samples show large reductions in J c at all temperatures and fields compared to those grown on bare LaAlO 3 , correlating to both a-axis grain and nonsuperconducting phase formation. With additional optimization, LNO could be a promising buffer layer for both YBCO and Tl-based superconducting films, perhaps ideally suited for coated conductor applications

  17. Nernst effect of Ni-doped NdBa2Cu3O7-δ and transport properties in UPt2Si2

    International Nuclear Information System (INIS)

    Johannsen, Niko

    2008-05-01

    In this thesis, the Nernst effect in high-temperature superconductors is investigated. Large Nernst voltages were found to survive up to temperatures that reach far out of the superconducting phase. This was extensively studied thereafter in wide doping range of the high-T c 's. We were able to significantly expand these studies by tuning T * and T ν independently. This was done by inducing Ni ions into the CuO planes of NdBa 2 {Cu 1-y Ni y } 3 O 7-δ which allowed to study the Nernst effect in a wide parameter range. This is done on one hand in dependence of the oxygen content which varies the charge carrier concentration. On the other hand, the Ni concentration is varied from 0% to 12%, thereby enhancing T * and simultaneously suppressing T c with increasing concentrations. The temperatures to which the anomalous Nernst signal is detectable is the onset temperature T ν . The goal of this work was to find out whether T ν follows T c or T * . The onset temperatures of the anomalous Nernst signals are determined as the slightest detectable deviation from the quasiparticle background above T c . In the second part of this work, the Nernst effect and other transport properties of UPt 2 Si 2 , including electrical ones such as the resistivity and the Hall effect and thermal ones, as the thermal conductivity, the thermopower and the Righi-Leduc effect were investigated. (orig.)

  18. Surface impedance of epitaxial films Y-Ba-Cu-O in short wave region of range millimetric

    International Nuclear Information System (INIS)

    Vojnovskij, I.V.; Pustyl'nik, O.D.; Boguslavskij, Yu.M.; Shapovalov, A.P.

    1992-01-01

    Epitaxial Y-Ba-Cu-O films on MgO substrate with perfect crystal structure are obtained due to nonaxial magnetron HF-spraying. Temperature dependence of the surface impedance of the films within 66 and 134 GHz frequency is studied. The obtained value of residual surface resistance within 134 GHz frequency (60 mohm) confirms high quality of the films

  19. High-temperature superconductors, as seen through the eyes of neutrons

    Directory of Open Access Journals (Sweden)

    Z. Yamani

    2006-09-01

    Full Text Available   Neutron scattering is proved to be a vital probe in unveiling the magnetic properties of high temperature superconductors (HTSC. Detailed information about the energy and momentum dependence of the magnetic dynamics of HTSC have been obtained directly by this technique. Over the past decade by improving the crystal growth methods, large and high quality single crystals of HTSC, which are essential for a neutron scattering experiment, have become available. The results of neutron scattering measurements on such crystals have considerably enhanced our understanding of the magnetism in HTSC both in the superconducting (SC and normal states. In this review, the neutron scattering results on two main HTSC families, La2-xSrxCuO4 (LSCOx and YBa2CuO3O6+x (YBCO6+x, are considered with an emphasis on the most prominent properties of these materials that are now widely accepted. These include the presence of strong antiferromagnetic (AF fluctuations even in optimally doped region of the phase diagram, neutron resonance peak that scales with SC transition temperature, Tc, incommensurate magnetic fluctuations (stripes, and a pseudogap in the normal state of underdoped materials.

  20. Effect of rare-earth composition on microstructure and pinning properties of Zr-doped (Gd,Y)Ba2Cu3Ox superconducting tapes

    International Nuclear Information System (INIS)

    Selvamanickam, V; Zhang, Y; Guevara, A; Shi, T; Yao, Y; Majkic, G; Galtsyan, E; Chen, Y; Lei, C; Miller, D J

    2012-01-01

    The effect of changing Gd + Y content from 1.2 to 1.6 in the precursor of (Gd,Y)Ba 2 Cu 3 O 7 superconducting thin film tapes made by metal organic chemical vapor deposition (MOCVD) at a constant Gd:Y ratio and a fixed Zr content of 7.5% has been studied. The influence of changing the Gd:Y ratio from Gd = 0 to Y= 0 in 0.2 mol steps at a constant Gd + Y content of 1.2 in the precursor has also been investigated at a fixed Zr content of 7.5%. The critical current of these films is found to vary significantly as a function of rare-earth content as well as a function of rare-earth type. Even for a fixed Zr content, it is found that the critical current in the orientation of magnetic field parallel to the a–b plane and that in the orientation of field perpendicular to the a–b plane can be systematically varied with changing Gd + Y content as well as with changing Gd:Y ratio. The nanoscale defect structures along the a–b plane and along the c-axis are found to be sensitive to these changes in rare-earth content and type. (paper)