Search

This study examined the impact of adding hard ferrite Ba0.5Sr0.5Fe12O19 (BSF) nanoparticles to the Bi1.8Pb0.4Sr2Ca2Cu3.2O10+δ (Bi, Pb)-2223) superconductor phase. The investigation specifically focused on evaluating the critical current density, fluctuation-induced conductivity, and magnetoresistance of nano-(BSF)x/(Bi, Pb)-2223 composite, where 0.00 ≤ x ≤ 0.20 wt.%. The results revealed that the critical current density, Jc, increased with the addition of nano-(BSF) up to x = 0.04 wt.%, reaching a value of 441.20 A/cm2. The Aslamazov and Larkin (A–L) approach has been evaluated the fluctuation-induced conductivity. Several superconducting parameters, including coherence length ζc(0), effective layer thickness d, penetration depth λpd(0), and Fermi energy E F showed improvement as the concentration of nano-(BSF) increased up to x = 0.04 wt.%. In addition to Ginzburg–Landau critical parameters, such as the thermodynamic critical field Bc(0), lower critical magnetic field Bc1(0), upper critical magnetic field Bc2(0), and critical current density Jc(0) demonstrated an increase up to x = 0.04 wt.%, followed by a decrease for higher concentrations. The magnetoresistance measurements were performed at various applied DC magnetic fields, with values ranging from 0.29 to 4.44 kG, and were analyzed using the thermally activated flux creep (TAFC) and Ambegaokar–Halperin (AH) models. The calculated flux pinning energy (U) increased with the addition of nano-(BSF) up to x = 0.04 wt.% and then decreased for x > 0.04 wt.%. Furthermore, the transition width (ΔT), was observed to increase as the applied magnetic field values increased. Moreover, the addition of nano-(BSF) increased the field-independent critical current density, Jc,0(0), up to x = 0.04 wt.%, after which it decreased for higher concentrations. [ABSTRACT FROM AUTHOR]

The effect of Arsenic substitution on the properties of Bi-2212 superconductors was studied. Solid-state reaction technique was used for the synthesis of Bi2−xAsxSr2Ca1.1Cu2.1O8 samples, x = 0, 0.1, 0.2 and 0.4. The X-ray diffraction confirmed the formation of the tetragonal phase of Bi-2212 superconductors. The decrement in the c parameter confirmed that As insertions were introduced into the Bi sites of the system. The grain morphology of the surface was analysed by scanning electron microscopy, where the amount of arsenic increases with As substitution. The superconducting transition temperature (Tc) was determined from the DC-electrical resistivity by the standard four-probe technique. Tc was enhanced up to x = 0.1 above which it was suppressed. For magnetism, half magnetic-hysteresis loops were obtained by SQUID magnetometer at different temperatures (5 and 30 K). The hysteresis loops sizes increased with increasing As-concentrations. The critical current density (Jc) and the flux pinning mechanisms were investigated via different models. [ABSTRACT FROM AUTHOR]

The effect of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) addition on the phase formation and the superconducting properties of GdBa2Cu3O phase has been studied. Therefore, composite superconductor samples of type (CNTs) GdBa2Cu3O, 0.0 0.1 wt.% have been synthesized by a standard solid-state reaction technique. The samples have been characterized using X-ray powder diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results of XRD show an enhancement in the phase formation up to 0.06 wt.% and 0.08 wt.% for SWCNTs and MWCNTs, respectively. SEM and TEM reveal that CNTs form an electrical network resulting in well-connected superconducting grains. The electrical properties of the prepared samples have been examined by electric resistivity and I-V measurements, and their results reinforce the XRD, SEM and TEM. Consequently, both and improve as the addition percentage increases up to 0.06 wt.% and 0.08 wt.% for SWCNTs and MWCNTs, respectively. [ABSTRACT FROM AUTHOR]

Superconductor samples of type (CoFeO)xGdBaCuO (0≤ x≤0.1) were synthesized by the conventional solid-state reaction technique, whereas nanosized CoFeO was prepared by co-precipitation method with grain size of about 8.5 nm. The elemental content of the prepared samples was determined using particle induced X-ray emission (PIXE). The temperature dependence of real (χ') and imaginary (χʺ) components of AC magnetic susceptibility (ACMS) at different magnetic field amplitude (3-15 Oe) was investigated. The analysis of the temperature dependence of ACMS was performed using Bean critical state model. The values of the critical current density J at T > T ( T is the inter-granular loss peak temperature) were calculated as a function of magnetic field and nanosized CoFeO content. It was found that the low nanosized CoFeO addition content ( x = 0.01) improves the critical current density J of Gd-123 superconducting phase. The observed variation of J with temperature indicated that the weak links are changed from superconductor-normal metal-superconductor (SNS) for free sample to superconductor-insulator-superconductor (SIS) type of junctions for samples added with nanosized CoFeO of x > 0.01. We also discussed the experimental results in the framework of the critical state model to estimate the effective volume fraction of the grains f using Cole-Cole plots. [ABSTRACT FROM AUTHOR]

Bulk superconducting samples of type GdBaCuRuO phase, Gd-123, with x ranging from 0.0 to 0.15 were prepared by the conventional solid-state reaction technique. X-ray powder diffraction (XRD) and the electrical resistivity measurements were performed in order to investigate the effect of Ru ions substitution on Gd-123 phase. Enhancement of the phase formation and the superconducting transition temperature T for GdBaCuRuO phase up to x=0.05 was observed. The effect of magnetic field up to 4.4 kG on the electrical resistivity behavior of the prepared samples was studied to investigate the flux motion of this phase. The derived flux pinning energy U, based on the thermally activated flux creep TAFC model, decreased with increasing the magnetic field B. The flux pinning energy followed the exponent behavior as U( B)∼ B. The superconducting transition width ΔT increased as the magnetic field increased, showing the scaling relation as ΔT∼ B. Using Ambegaokar and Halperin AH theory, the magnetic field and temperature dependence of U was found to be U( B, T)∼ ΔTB, η= β+ n. The critical current density J(0) enhanced up to x=0.05, beyond which it decreased with further increase in Ru-content. [ABSTRACT FROM AUTHOR]

Bulk superconducting samples of type TlPbSrBaCaCuRuO, (Tl,Pb)/Sr-1212, with 0.0≤ x≤0.525 were synthesized by the conventional one-step solid-state reaction technique via a short time, using SrO instead of SrCO. X-ray powder diffraction XRD, scanning electron microscope SEM and the electrical resistivity measurements at different applied dc magnetic fields (0.0-4.4 kG) were performed in order to investigate the effect of Ru ions substitution on (Tl,Pb)/Sr-1212 phase. Enhancement of the phase formation, the superconducting transition temperature T and the hole carriers concentration P was observed up to x=0.075, and they decreased for further increase in x. The magnetoresistance data of these samples were analyzed within the thermally activated flux creep TAFC model and the Ambegaokar and Halperin AH theory. The derived flux pinning energy U, the critical current density J(0) and the upper critical magnetic field B(0) enhanced up to x=0.075, beyond which they decreased for further increase in Ru-content. The coherence length at 0 K ζ(0) decreased up to x=0.075 and increased with x>0.075. In addition, we reported a comparison between the effect of Ru substitution on the physical properties for Gd-123, (Bi,Pb)-2223 and (Tl,Pb)/Sr-1212 phases. [ABSTRACT FROM AUTHOR]

Abstract: Cu0.5Tl0.5Ba2Ca2−x Cd x Cu3O10−δ superconductor samples (x =0–0.8) were prepared by a single-step solid-state reaction technique in order to investigate the effect of Cd-substitution on the formation and the transport properties of the (Cu, Tl)-1223 phase. A nearly single-phase materials is synthesized with x =0.2 and found to have optimum superconducting transition temperature T c and critical current density J c. The dielectric constant and the loss tangent, for all the prepared samples, were measured at room temperature as a function of frequency up to 5MHz. The normal dielectric constant is strongly dependent on Cd-content and correlates with the normal electrical resistivity results. This correlation was discussed according to the grain boundaries scattering. [Copyright &y& Elsevier]

The effect of nano-size MgO (40–60 nm) addition on the physical properties of polycrystalline (Cu0.25Tl0.75)-1234 was studied. The MgO-concentration ( x) varied from 0.0 to 1.0 wt.% of the sample’s total mass. X-ray analysis, granular structure examination, energy dispersive X-ray spectroscopy, electrical resistivity, critical current density at different applied magnetic fields and Vickers microhardness measurements were carried out to study the performance of these samples. Phase examination by X-ray diffraction indicated that MgO-addition enhanced the (Cu0.25Tl0.75)-1234 phase formation till x=0.6 wt.%. Granular investigation by scanning electron microscope reveled that both number and size of voids decreased as x increased from 0.0 to 0.6 wt.%. These results were supported by the sample’s porosity calculation. The superconducting transition temperature and critical current density were found to have optimum values at x=0.6 wt.%. Furthermore, the Vickers microhardness increased till x=0.6 after that it decreased with further increase in x. [ABSTRACT FROM AUTHOR]

Abstract: The effect of partial replacement of copper by zinc in Tl2Ba2Ca2Cu3O10−δ superconductor phase is studied. Superconducting samples of the nominal composition Tl2Ba2Ca2Cu3−x Zn x O10−δ with x ranging from 0 to 0.6 are prepared under normal pressure by a one step of solid-state reaction technique. The samples are characterized by using X-ray powder diffraction, scanning electron microscope (SEM) and EDX. The X-ray data indicate that the partial replacement of Cu2+ions by Zn2+ions does not influence the tetragonal structure of the samples, and the lattice parameters a and c vary according to the difference in the ionic radii of Cu and Zn. The superconducting parameters, such as superconducting transition temperature T c, critical current density J c and irreversibility field B ir are calculated from electrical resistivity and AC-magnetic susceptibility measurements. [Copyright &y& Elsevier]