BiSrCaCu Oxide Research Articles

Phase characterization in three monofilament BSCCO 2223/Ag tapes

The nonsuperconducting (non-SC) phases present in three BSCCO (Bi-Sr-Ca-Cu oxide) tapes have been identified. These tapes were obtained from precursor powder produced by three different routes and the microstructural characterization was conducted using scanning electron microscopy and X-ray diffraction. The phases: alkaline earth cuprate (Ca,Sr) 2CuO (AEC 2:1), CuO and a Pb-rich phase (CaPbO 4+(Pb,Bi) 3Sr 2Ca 2CuO x ) were quantified using an imaging analyzer software on a cross-section after 50, 110, 170 and 230 h exposures at 820°C, which were performed between mechanical pressing operations. The correlation between critical current density ( J c) and non-SC phases showed that there is no direct correlations between the global quantity of non-SC phases and J c. Moreover, a good performance appeared to be highly dependent on many other factors, such as texture alignment and non-SC distribution.

Microstructural investigation of Bi-Sr-Ca-Cu-oxide thick films on alumina substrates

The microstructure of Bi-Sr-Ca-Cu-oxide (BSCCO) thick films on alumina substrates has been characterized using a combination of X-ray diffractometry, scanning electron microscopy, transmission electron microscopy of sections across the film/substrate interface and energy-dispersive X-ray spectrometry. A reaction layer formed between the BSCCO films and the alumina substrates. This chemical interaction is largely responsible for off-stoichiometry of the films and is more significant after partial melting of the films. A new phase with fee structure, lattice parameter a = 2.45 nm and approximate composition Al3Sr2CaBi2CuOx has been identified as reaction product between BSCCO and Al2O3.

Mechanical processing of highjcbscco superconductors

Abstract High J c superconducting oxides can be obtained by processing polycrystalline powders to achieve high degrees of densification and sharp crystallographic textures characterized by the conducting crystallographic planes lying parallel to the direction of the current flow (i.e., in the plane of a conducting tape or parallel to the axis of a wire). In the present study, we investigate the densification and texture evolution in a Pb doped Bi—Sr—Ca—Cu oxide (BSCCO) under axisymmetric and plane strain (channel die) compression. Experimental measurements of the microstructural evolution, including crystallographic texture and grain morphology, are presented as a function of the degree of deformation and densification. The orientations of the conducting planes (c planes) are shown by measured X-ray pole figures and analyses of these orientations are given for both tests. A model based on crystal plasticity theory is proposed to simulate the inelastic deformation and texturing of the BSCCO oxide. Predicte...

Preparation and critical current densities of highly textured 2212 BiSrCaCu oxide layers on silver

Doctor blade processed green tapes and screen printable pastes on silver foil, both prepared with Bi 2 Sr 2 Ca 1 Cu 2 O x powder, were subjected to melt-texturing using melting and crystallization temperatures derived from DTA measurements. Highly textured layers were formed by slow cooling from the melting temperature to the crystallization temperature and quenching after a holding period. Quenching increased T c to 90 K. The critical current density was measured as a function of temperature and magnetic field. At 4.2 K and 77 K and 0 Tesla, critical current densities as high as 1.3 × 10 5 A/cm 2 and 1.04 × 10 4 A/cm 2 were observed, respectively. At 4.2 K and 10 Tesla a critical current density of up to 5 × 10 4 A/cm 2 was obtained, even with B ⊥ tape

Preparation of single phase bismuth-based 2212 and 2223 superconducting oxides, and quantitative X-ray diffraction analysis of 2212 and 2223 phase mixtures

The preparation of single phase superconducting BiSrCaCu oxide powders with the nominal structural formulae Bi 2Sr 2Ca 2Cu 3O 10 and Bi 2Sr 2CaCu 20 8 from precursor oxide and carbonate mixture compositions with or without lead doping is described. In the absence of lead doping it is found that precursor compositions ranging from the stoichiometric ratio for the 2212 phase to the stoichiometric ratio for the 2223 phase yield only the ‘80K’ 2212 phase superconductor according to X-ray diffraction analysis. To synthesise the ‘110K’ 2223 phase it is necessary to dope with lead and to use the non-stoichiometric precursor composition, corresponding to Bi 1.84Pb 0.34Sr 1.91Ca 2.03Cu 3.060 y, established by Koyama et al. If the carbonate sources of the strontium and calcium oxides, plus copper oxide, are precalcined together before being combined with the bismuth and lead oxides (following the method of Arendt et al.) and the mixture is then calcined using a modification of the Koyama procedure, single phase 2223 material is produced. X-ray diffraction spectra from powder mixtures containing known proportions of the 2212 and 2223 phases are used to construct intensity ratio calibration curves for quantitative analysis of samples containing the two compounds.

Thin films of BiSrCaCu oxide prepared by laser evaporation

We have prepared BiSrCaCuO superconducting thin films by the pulsed laser evaporation method, using a YAG or an ArF excimer laser. The as-deposited films, which were enriched in Cu with respect to the bulk target composition Bi2Sr2Ca1Cu2O8 (i.e., the “2212” phase), were converted into the superconducting phase by a subsequent high temperature annealing in oxygen. Resistivity measurements showed superconducting transitions near 90 K, and the highest zero resistivity temperature was 83 K. The influence of the deposition parameters (photon wavelength) and annealing conditions (temperature, duration, and atmosphere) have been studied. The composition and in-depth distribution of the various elements were determined by Rutherford backscattering spectrometry (RBS), and the surface morphology was studied by scanning electron microscopy (SEM).

Magnetic and microwave studies of BiSrCaCu oxide superconductors

Abstract The temperature dependent resistivity, diamagnetic susceptibility and low field microwave absorption have been measured for Bi based copper oxides. The sharp change of slope in χ( T ) around T =50 K seems to indicate a new superconducting phase. The interpretation of ϱ( T ) and χ( T ) data by means of glassy state leads to the average size of the loop to be much smaller than the size of the grains. The lower critical field H c1 ≈40 mT at 4 K. We have not found any correlation between H c1 and the extremum of low field microwave absorption.

Structural and microstructural characterization of a high T c superconducting BiSrCaCu oxide

The crystal structure and microstructures of a high Tc BiSrCaCuO (BSCCO) compound were characterized by transmission electron microscopy, x-ray diffraction (XRD), and energy dispersive spectrometry (EDS). Convergent beam electron diffraction (CBED) analysis established that the crystal is of mm2 symmetry. Combined with electron diffraction, XRD, and EDS data, the high Tc superconducting BSCCO compound was found to be of the Pnn2 space group, orthorhombic in structure with a=0.540 nm, b=2.689 nm, and c=3.040 nm and with an approximate composition of Bi2Sr2CaCu2Oy. Diffraction contrast analysis indicated that the dislocations are predominantly of screw character with [010] or [001] Burgers vectors. However, edge type dislocations and dislocations with [100] Burgers vector were also observed. The magnitude of the Burgers vector along the [100] direction was determined to be 1/2 [100] by high-resolution lattice imaging. Stacking faults and small-angle grain boundaries were frequently observed. The presence of a high density of defects in the superconducting oxide may facilitate the processing of the material and serve as effective flux line barriers.

Structural analysis of superconducting ( TC = 105 K) BiSrCaCu oxide

The new high-T C BiSrCaCu oxide is studied by transmission electron microscopy. A pseudo tetragonal orthorhombic phase with lattice parameters a= 0.544 nm, b≈ a, and c= 3.70 nm was found. Its structure is similar to another BiSrCaCu oxide phase with lattice parameters a= 0.537 nm, a≈ b, c=3.09 nm which has a superconducting transition at T C = 75 K. The microstructure of the ( T C = 105 K) phase shows a high density of planar defects on {001} planes. Such defects are either (i) stacking faults (ii) phase boundaries or (iii) twin boundaries.

Structural analysis of superconducting (T c = 75 K) BiSrCaCu oxide

The new high-T c BiSrCaCu oxide is studied by transmission electron microscopy. Electron diffraction reveals that a BiSrCaCu oxide phase exists which has a pseudo tetragonal orthorhombic lattice with lattice parameters a = 0.537 nm, b≈a and c = 3.09 nm and a fivefold superstructure parallel to the b axis. The structure of this phase can be described by a primitive orthorhombic lattice. Strongly excited reflections satisfy conditions for a face centered lattice. Stacking faults and twins on {001} planes are observed within the grains.