The effect of Bi-2212 phase on the weak link behavior of Bi-2223 superconductors
15 Mar 2004-Physica C-superconductivity and Its Applications (North-Holland)-Vol. 403, Iss: 1, pp 60-66
TL;DR: In this paper, a systematic study of the weak link behavior for (Bi,Pb)2Sr2Ca2Cu3Oy (Bi-2223) polycrystalline samples has been done using the electrical resistivity and AC susceptibility techniques.
Abstract: A systematic study of the weak link behavior for (Bi,Pb)2Sr2Ca2Cu3Oy (Bi-2223) polycrystalline samples has been done using the electrical resistivity and AC susceptibility techniques. In this project, we have prepared a series of Bi-2223 samples with different fractions of Bi-2212 phase and investigated its effect on the intergranular properties. It was found that the Bi-2212 phase exist within the grain boundaries, play a role of weak links and consequently reduces the intergranular coupling. Analysis of the temperature dependence of the AC susceptibility near the transition temperature (Tc) has been done employing Bean’s critical state model. The observed variation of intergranular critical current densities (Jc) with temperature indicates that the Jc decreases with the amount of Bi-2212 phase.
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TL;DR: In this article, the effects of Li substitution on the properties of high temperature superconductor Bi17Pb0.3Sr2C2Cu3−x Li
Abstract: The effects of Li substitution on the properties of high temperature superconductor Bi17Pb0.3Sr2C2Cu3−x
Li
x
O
y
were investigated. The samples were prepared by substituting Li (x=0.00–0.20) with changing ratios by a solid state reaction method. The samples were characterized by X-ray diffraction, DC electrical resistivity, AC magnetic susceptibility, and scanning electronic microscopy (SEM). The X-ray diffraction studies were done at room temperature and the lattice constants of the material were determined by indexing all the peaks observed. This study shows that there are two coexisting phases; high-T
c
(2223) phase and low-T
c
(2212) phase. The lattice structure of the material belongs to the orthorhombic unit cell. The volume fraction was estimated from the intensities of Bi-(2223) and Bi-(2212) phases. The sample with 20 wt% of added Li showed the higher volume fraction of Bi-(2223) phase formed (81%) compared to the other samples. The DC electrical resistivity of all the samples decreased as the wt% of Li increased. Both the onset critical temperatures T
c
(onset) and zero electrical resistivity critical temperatures T
c
(R=0) of the samples were determined from the DC electrical resistivity measurements. The observed value of the onset critical T
c
(onset) temperature was 110 K agreeing well with the magnetic susceptibility measurements. We obtained T
c
onset at 112 K from AC magnetic susceptibility measurements.
80 citations
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TL;DR: In this article, the X-ray diffraction technique, scanning electron microscope, electrical and thermoelectric power measurements were used to characterize the prepared samples and showed that all the samples under investigation are p-type materials with hole carriers predomination over the measured temperature range.
Abstract: (2223) phase is synthesized by solid state method. The X-ray diffraction technique, scanning electron microscope, electrical and thermoelectric power measurements were used to characterize the prepared samples. The samples are sintered from 1123 K to 1143 K and the effect of sintering on the structural and transport properties was investigated. All the above measurements showed that in the samples, there is nearly single (2223) phase. The Seebeck coefficient measurements shows that all the samples under investigation are p-type materials with hole carriers predomination over the measured temperature range. Using the electrical resistivity and TEP data, the power factor S 2 / ρ was calculated and exhibits good indication to wide application of the investigated compositions as thermoelectric materials.
35 citations
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TL;DR: Magnesium substitution has been found to improve the interplane coupling in the unit cell of Cu0.5Tl 0.5Ba2Ca2?yMgyCu3O10??, which in turn would enhance the intergranular coupling.
Abstract: The intergranular properties of Cu0.5Tl0.5Ba2Ca2?yMgyCu3O10?? superconductor have been studied by resistivity and AC magnetic susceptibility measurements. Magnesium substitution has been found to improve the interplane coupling in the unit cell of Cu0.5Tl0.5Ba2Ca2?yMgyCu3O10??, which in turn would enhance the intergranular coupling. The main objective of the present studies was to observe any possible role played by Mg doping in developing and enhancing the intergranular coupling and flux pinning properties of this compound. Any improvement to the intergrain coupling may be promoted by a change in the oxygen content in the final compound. Since the loss and/or intake of oxygen occurs at Ta?350??C, the post-annealing experiments were carried out at 500??C for 3?h in air, nitrogen and oxygen atmospheres. It was observed from these studies that the oxygen contents decreased in all the samples after post-annealing in air, nitrogen and oxygen atmospheres. The most prominent effects in terms of enhanced superconductivity in the intergranular regions are observed in Mg-doped samples after post-annealing in air. The Mg-doped samples have shown enhanced granular connectivity, since the intergranular coupling peak observed in ?'' in AC susceptibility measurements is shifted to higher temperatures with the increase of Mg concentration. The enhanced intergranular coupling and flux pinning in magnesium-substituted samples is also observed in AC susceptibility measurements in external magnetic fields. The enhancement of intergranular coupling increases the transport critical current density of the samples.
28 citations
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TL;DR: In this article, the effects of Eu2O3 nanoparticles addition to BSCCO superconducting system, four bulk polycrystalline samples were prepared by chemical sol-gel method.
Abstract: To study the effects of Eu2O3 nanoparticles addition to BSCCO superconducting system, four bulk polycrystalline samples with general formula of Bi1.6Pb0.4Sr2Ca2Cu3Oy+xEu2O3 (where x=0.0, 0.3, 0.5, 1.0 wt%) were prepared by chemical sol–gel method. X-ray diffraction, SEM, and TEM were used for structural characterization of the samples. DC electrical resistivity, critical current, and AC magnetic susceptibility were measured. XRD analysis showed that both (Bi,Pb)-2223 and Bi-2212 phases coexist in the samples having orthorhombic crystal structure. DC electrical resistivity, Jc, and AC magnetic susceptibility measurements reveal that adding Eu nanoparticles to BSCCO improves superconducting properties of this system and enhances its critical current density. The enhancement of the Jc may be caused by improvement of the grain connectivity with Eu nanoparticle additions.
25 citations
Cites background from "The effect of Bi-2212 phase on the ..."
...All the samples displayed a metallic character above onset temperature, which is defined as the temperature where R–T plot deviates from linearity [10]....
[...]
...4 was selected for preparing the samples in this report [9, 10]....
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TL;DR: In this article, the effect of alumina nanoparticles on phase formation and superconducting properties of Bi1.6Pb0.4Sr2Ca2Cu3O10−y system has been investigated.
Abstract: In this work, the effect of alumina (α-Al2O3) nanoparticle addition on the phase formation and superconducting properties of Bi1.6Pb0.4Sr2Ca2Cu3O10−y
((Bi,Pb)-2223) system has been investigated. Six samples with different alumina nanoparticle contents (0.0, 0.1, 0.2, 0.3, 0.5, and 1 wt % of the sample’s total mass) were prepared by conventional solid-state reaction. X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods have been used to study phase formation and microstructure of the prepared samples, respectively. Also, electrical resistivity and critical current density of the prepared samples were measured by four-probe technique. AC susceptibility of the samples has been measured by an LCR meter. XRD results showed that addition of small amounts of the alumina nanoparticles improves (Bi,Pb)-2223 phase formation significantly. Temperature dependency of AC susceptibility measurements revealed that addition of α-Al2O3 nanoparticles improves the intergranular coupling. The I-V measurements show that critical current density of samples increased from about 36 A/cm 2 for the alumina nanoparticle-free sample to about 107 A/cm 2 for the sample with 0.5 wt % α-Al2O3 nanoparticles.
22 citations
Cites background from "The effect of Bi-2212 phase on the ..."
...The (Bi,Pb)-2212 phase on the grain boundaries plays the role of weak links likely and consequently reduces the intergranular coupling [29]....
[...]
...Below TcJ, the grains are coupled, or in other terms, phaselocked with zero phase difference across the intergranular junctions [7, 29]....
[...]
References
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TL;DR: Experimental results and phenomenological theory based on the sponge model for hysteretic high-field superconductors are given in this article, where the response of the supercondors to alternating fields superimposed upon steady fields is studied.
Abstract: Experimental results and phenomenological theory based on the sponge model for hysteretic high-field superconductors are given. After developing the exposition for static magnetization, the response of the superconductors to alternating fields superimposed upon steady fields is studied. (T.F.H.)
3,634 citations
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IBM1
TL;DR: The grain-boundary critical current densities in bicrystal films prepared by evaporation and postannealing and by laser ablation are in good agreement; this result demonstrates that the transport properties are insensitive to preparation technique and, thus, are not dominated by the diffusion of substrate impurities into the boundary region.
Abstract: Previous work on the superconducting transport properties of individual grain boundaries in thin-film bicrystals of YBa{sub 2}Cu{sub 3}O{sub 7} has been extended to provide a more comprehensive picture of their weak-link characteristics. Grain boundaries with three different geometries have been studied; the transport properties of all three types of boundaries are essentially identical, which implies that the poor superconducting coupling between grains is a result of the intrinsic structural disorder at the boundary. The grain-boundary critical current densities in bicrystal films prepared by evaporation and postannealing and by laser ablation are also in good agreement; this result demonstrates that the transport properties are insensitive to preparation technique and, thus, are not dominated by the diffusion of substrate impurities into the boundary region. High grain-boundary resistivities and low {ital I}{sub {ital c}R{ital n}} products imply that the boundaries act as strong barriers to current flow with locally depressed order parameters. Strong magnetic hysteresis, associated with trapped intragranular flux, is observed; this hysteretic behavior is also responsible for an increase in the grain boundary {ital J}{sub {ital c}} for {ital H}{sub {ital a}{ital p}{ital p}}{gt}300--500 Oe.
1,199 citations
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TL;DR: The ac susceptibility of sintered sintering pellets is measured as a function of temperature and ac magnetic field amplitude and frequency to find the value for an intergrain decoupling field, above which flux creep presumably becomes flux flow at the grain boundaries.
Abstract: We measured the ac susceptibility of sintered ${\mathrm{Y}}_{1}$${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ pellets as a function of temperature and ac magnetic field amplitude and frequency. The imaginary part of the susceptibility \ensuremath{\chi}'' exhibits two peaks. A narrow peak is located at the critical temperature of the grains. A broad peak at lower temperature is attributed to hysteresis losses at the grain boundaries. There is a small shift in this coupling peak to higher temperature as the frequency increases from 10 to 1000 Hz. We explain the shift in terms of Anderson flux creep on a time scale of milliseconds. The shift depends on the amplitude of the measuring field. The activation energy for flux creep ranges from 11.9\ifmmode\pm\else\textpm\fi{}1.0 eV in the zero-field limit [0.8 A ${\mathrm{m}}^{\mathrm{r}}$-r1(0.01 Oe)] to 1.2\ifmmode\pm\else\textpm\fi{}0.3 eV at 800 A ${m}^{\ensuremath{-}}$1(10 Oe). We extrapolate our data to find the value for an intergrain decoupling field of 1--2 kA m-1 (13--25 Oe), above which flux creep presumably becomes flux flow at the grain boundaries.
199 citations
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TL;DR: In this paper, a combination of atomic resolution Z-contrast imaging and bond valence sum analysis was used to demonstrate that the atomic structure of the grain boundary dominates the transport properties of high-T c oxide superconductors.
Abstract: Grain boundaries have long been known to have a deleterious and irreproducible effect on the transport properties of high- T c oxide superconductors, particularly in the high-angle regime where an exponential decrease in critical current has been reported. We demonstrate, through a combination of atomic resolution Z-contrast imaging and bond valence sum analysis, that it is the atomic structure of the grain boundary that dominates this behavior. [001] tilt grain boundaries in thin-film YBa 2 Cu 3 0 7− δ are composed of arrays of dislocations in defined sequences. The resulting strain fields seriously perturb the local electronic structure, leading to a non-superconducting zone at the grain boundary. The width of this zone increases linearly with misorientation angle, naturally explaining the observed exponential decrease in critical current. In addition, the widely varying J c measurements for a given grain boundary misorientation can be naturally explained by the facetting of the grain boundary plane.
136 citations
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TL;DR: In this article, a double step characteristic is observed at 76 K in the transport critical current as a function of magnetic field (10 -4 T to 10 T) in bulk sintered Y-, Bi-and Tl-based high-T c superconducting materials.
Abstract: A double step characteristic is observed at 76 K in the transport critical current as a function of magnetic field (10 -4 T to 10 T) in bulk sintered Y-, Bi- and Tl-based high- T c superconducting materials. The low-field, step-like drop in the critical current density J c commences at magnetic fields B between about 0.3 and 2 mT. This is followed by a plateau region of relatively constant critical current extending from about 30 to 300 mT, and then a second drop at fields between about 0.3 and 10 T. These features occur for all three superconductor materials and are interpreted respectively as a self-field/weak-link regime, a remnant percolation path regime and a flux-flow/upper-critical-field regime. The sharpness of the transition of the voltage-current ( V-I characteristic, represented by the transition parameter n (i.e., V ∝ I n ), has a similar double-step shape as a function of magnetic field directly corresponding to the features of the J c ( B ) characteristic.
132 citations