Critical Current Density and Intergranular Coupling Study of the Dysprosium Oxide Nanoparticle Added Bi1.6Pb0.4Sr2Ca2Cu3O y Superconductor

The dysprosium oxide nanoparticles’ addition effects on structural, DC electrical resistivity, critical current density, and AC magnetic susceptibility properties of polycrystalline Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O _y samples are investigated. X-ray diffraction (XRD) analysis showed that both (Bi,Pb)-2223 and Bi-2212 phases coexist in the samples having orthorhombic crystal structure. Bi-2223 phase concentration increases with increasing dysprosium nanoparticle concentration. DC electrical resistivity, critical current density (J _c), and AC susceptibility measurements reveal that adding dysprosium nanoparticles to bismuth–strontium–calcium–copper–oxide (BSCCO) improves superconducting properties of this system and enhances its critical current density due to the improvement of the grain connectivity with dysprosium nanoparticle addition.     

Electric,magnetic, and transport critical current density behavior of the 2201, 2212, and 2223 phases of ‘BSCCO’

We have studied the electrical properties of polycrystalline pellets of the high-T _c superconducting phases occurring in the Bi₂O₃-SrO-CaO-CuO (BSCCO) system, having nominal compositions Bi₂Sr₂Cu₁O_6+y, (2201 phase, withT _c = 10 K.) Bi₂Sr₂CaCu₂O_8+y (2212 phase, withT _c = 85 K), and Bi₂Sr₂Ca₂Cu₃O_10+y (2223 phase, withT _c = 110 K). Pellets containing the 2223 phase having zero resistance below 105 K were obtained. For the 2212 and 2223 phases, the transport critical current density was measured as a function of temperature and of the externally applied magnetic field. As previously found for YBa₂Cu₃O_7-x (YBCO), results are consistent with the occurrence of a weak superconducting coupling among the grains. Such coupling was, however, noticeably stronger for the 2223 phase than for the 2212 phase.     

On the synthesis and structure of single-phase (Bi,Pb)2Ca2Sr2Cu3O10

We report an elegant method for the synthesis of single-phase Bi-2223 superconductor from a stoichiometric composition Bi_1.7Pb_0.3Ca₂Sr₂Cu₃O_y by a matrix reaction route. The superconducting transition temperatureT _c (R=0) of this single-phase compound is 120 K. The effect of Pb-content and sintering temperature on the formation and stability of Bi-2223 phase is described.     

Effect of Nb addition on magnetic,structural and superconducting properties of (Bi,Pb)-2223 superconductors

In this work, the effects of Nb₂O₅ addition with different ratios on the structural and magnetic properties of Bi_1.7?xPb_0.3Nb_xSr₂Ca₂Cu₃O_y (x = 0.00–0.20) superconducting samples were investigated. (Bi, Pb)-2223 superconducting samples were prepared by conventional solid-state reaction method. The phase formation, phase fraction and lattice parameters were determined from X-ray powder diffraction (XRD) measurements, the microstructure, surface morphology analyses of the samples were carried out using scanning electron microscope (SEM). Additionally, ac susceptibility measurements were done in order to determine the critical current density (J_c) and hole concentration (p) of the samples. AC susceptibility measurements were done at various ac fields (ranging from 20 to 160 A/m) to understand the effect of Nb addition on magnetic properties of Bi_1.7?xPb_0.3Nb_xSr₂Ca₂Cu₃O_y superconductor. Critical onset (T _c ^on ) and loss peak temperatures (T_p) were estimated from the ac susceptibility curves. It was observed from ac susceptibility measurements that the critical onset temperatures decreased from about 108–98 K with increasing Nb addition (x = 0.00–0.20). The imaginary part of susceptibility was used to calculate the intergranular critical current density (J_c) by means of the Bean’s model. X-ray diffraction analysis revealed that the samples consisted of a mixture of Bi-2223 and Bi-2212 phases as the major constituents and non-superconducting phase Ca₂PbO₄ as the minor. It was also shown from XRD measurements that volume fraction of high-T_c phase decreases with increasing Nb addition up to x = 0.20. The sample with Nb addition of x = 0.20 showed the highest volume fraction of Bi-2223 phase (86 %). When Nb addition was increased, the surface morphology and grain connectivity are found to degrade, the grain sizes decrease and porosity of the samples were observed to increase from SEM images except the sample with x = 0.20 Nb addition.     

The Effects of Mg Substitution in Bi-2223 Superconductors

The effects of Mg substitution in Bi-2223 superconductor system has been studied for the Bi_1.7Pb_0.3Sr₂Ca₂Cu_3−x Mg _x O _y nominal composition (x=0.00, 0.05, 0.10, 0.15 and 0.20) which was prepared by the conventional solid-state reaction. The properties of these compounds have been investigated by measuring the electrical resistivity, X-ray diffraction (XRD) and density. Also, scanning electron microscopy (SEM) was employed to investigate the surface microstructure of the samples. It has been found that the effects of Mg substitution support the development of both the Bi-2212 and Bi-2223 phases. These measurements and analyses enable us to discuss the effects of Mg dopant on superconducting properties. We found that onset critical temperatures (T _c, onset) decrease with addition x>0.10 in resistivity measurements. The presence of Mg influenced the microstructure of the samples and decreased the mean grain size of Bi-2223 grains up to x=0.10.     

Doping of Bi-Sr-Ca-Cu-O Compounds with Mn

Formation of the superconducting phases Bi-2212 and Bi-2223 has been studied for samples with nominal composition Bi_aPb_bMn_cSr₄Ca₅Cu₇O _x (a + b + c = 4). The influence of the stoichiometric replacement of Bi and/or Pb by Mn on the electric and magnetic properties of the Bi-based superconductors has been studied. The partial substitution of Mn for Bi in the samples without Pb did not promote the growth of the Bi-2223 phase. The samples with double substitution Pb-Mn for Bi revealed a large amount of the Bi-2223 phase.     

The Effect of Mn Substitution on Properties of Bi1.6Pb0.4Sr2Ca2?x Mn x Cu3O y Superconductors

The effects of Mn substitution on the physical properties and structural characteristics of Bi_1.6Pb_0.4Sr₂Ca₂Cu_3−x Mn _x Oy (Bi-2223) superconductor system have been studied. For this, the samples of nominal composition Bi_1.6Pb_0.4Sr₂Ca₂Cu_3−x Mn _x Oy (x=0.00, 0.10, 0.15 & 0.20) was prepared by the solid-state reaction method. It has been found that the effects of Mn substitution favor the formation of Bi-2223 phases. The phase identification/gross structural characteristics of synthesized (HTSC) materials explored through powder X-ray diffractometer reveals that all the samples crystallize in orthorhombic structure with lattice parameters (a=5.4918 ?, b=5.4071 ?, and c=37.0608 ?) up to Mn concentration of x=0.20. The critical transition temperature (T _c) measured by standard four probe method has been found to depress from 108 K to 70 K and transport current density (J _c) has been increased from 4.67×10² to 3.52×10³ A cm⁻² as Mn content (x) increases from 0.00 to 0.20. The surface morphology investigated through scanning electron microscope and atomic force microscopy (SEM and AFM) results that voids and grains size increases as the Mn concentration increases besides the nanosphere like structures on the surface of the Mn doped Bi-2223 sample.     

Enhanced Electrical Transport Properties of Nano NiFe2O4-added (Bi1.6Pb0.4)Sr2Ca2Cu3O10 Superconductor

The effect of nanometer sized NiFe₂O₄ (∼15 nm) addition in Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O₁₀ (Bi2223) superconductor was studied. The (Bi_1.6Pb_0.4)Sr₂Ca₂Cu₃O₁₀ superconductor was prepared through the co-precipitation method and 0.01 wt% to 0.05 wt% of nano NiFe₂O₄ was added. The critical temperature (T _c), critical current density (J _c), phase formation and microstructure were investigated. All samples showed a major Bi2223 phase with (Bi,Pb)₂Sr₂CaCu₂O₈ (Bi2212) as the minor phase. The sample with 0.01 wt% nano NiFe₂O₄ showed the highest T _c and J _c: of more than 3 orders of magnitude higher than the non-added sample at 77 K. A further nano NiFe₂O₄ addition (>0.01 wt%) leads to degradation of T _c and J _c. These results indicate that addition of an optimum amount of NiFe₂O₄ nanoparticles can effectively enhance the transport critical current density in this system.     

Effect of Eu2O3 Nanoparticles Addition on Structural and Superconducting Properties of BSCCO

To study the effects of Eu₂O₃ nanoparticles addition to BSCCO superconducting system, four bulk polycrystalline samples with general formula of Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O _y +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, J _c , 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 J _c may be caused by improvement of the grain connectivity with Eu nanoparticle additions.     

Improvement of the critical current density in Bi-2223 ceramics by sodium–silver co-doping

Bi_1.46Pb_0.36Ag_0.18Sr₂Ca₃Cu_4?xNa_xO_y (x = 0, 0.05, 0.1 and 0.25) samples were prepared by a conventional solid state reaction method. The prepared samples are characterized using X-ray powder diffraction, scanning electron microscope, dc electrical resistivity and magnetic-hysteresis loop measurements. It has been shown that the Na doping in low contents significantly improves the physical properties of Bi-2223 phase. Magnetic hysteresis measurements have shown that the largest hysteresis curve belongs to Bi_1.46Pb_0.36Ag_0.18Sr₂Ca₃Cu_3.95Na_0.05O_y sample including x = 0.05 Na content, indicating that it has best flux pinning capability in samples produced in this work. In addition, J_c values of the samples were calculated from the hysteresis loop measurement by using the Bean’s model showing that J_c increases with small amounts of sodium–silver co-doping.     

The Effect of Barium Doping on the Selective Structure of Bi-2223 Phase

The partial substitution of Sr by Ba in the two nominal compositions of Bi_1.8Pb_0.4Sr_2−x Ba _x Ca_2.2Cu₃O _y [x=0.0, 0.1, 0.2, and 0.3 (A group)] and Bi_1.66Pb_0.34Sr_2−x Ba _x Ca₂Cu₃O _y [x=0.0, 0.1, 0.2, 0.3, 0.4, and 0.5 (B group)] have been investigated by resistivity, ac susceptibility measurements and by XRD and SEM analysis. In general, the nature of the temperature dependence of resistivity and susceptibility measurements indicate the presence of a superconducting transition between grains coupled by weak links. However, the XRD and SEM analyses show that the relative composition of initial elements used in Bi-(2223) is essential to the site that is selected by the Ba ions. In the A group, Ba doping up to x=0.1 will improve the phase formation of Bi-2223, and improve the superconductivity properties of the samples. In the B group, although Ba doping up to x=0.1 will enhance the phase formation of Bi-2223, it will decrease the coupling between the grain and the superconductivity properties of these systems. The presence of lower Tc phases will begin to appear for x>0.1, in both of these systems. The superconductivity properties and the phase formation of Bi-(2223) will decrease as the Ba concentration increases.     

The Investigation of the Weak Link Behavior in the Niobium (Nb) Doped Bi1.6Pb0.4Sr2Ca2Cu3O δ Superconductor

The Nb substitution effect on structural, DC electrical resistivity, and AC susceptibility properties of polycrystalline Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O _δ samples is investigated. The behavior of weak link and intergranular coupling in the substituted samples is discussed. While the Bi-2223 phase concentration increases in the X-ray diffraction (XRD) pattern, the intragrain transition temperature remains nearly unchanged in the substituted samples. The intergrain transition temperature is changed with Nb substitution.     

Effect of Tungsten (W) Substitution on the Physical Properties of Bi-(2223) Superconductors

The superconducting Bi_1.6Pb_0.4Sr₂Ca₂Cu_3?x W _x O_10+y (x=0.00, 0.05, 0.10, 0.15) bulk samples were prepared by the solid-state reaction method. The effects of W substitution on the BSCCO system have been investigated by the electrical resistivity (ρ-T), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), magnetic hysteresis and critical current density measurements. It has been found that the Bi-(2212) low-T _C phase is formed for all the substitution levels, together with the Bi-(2223) high-T _C phase. The results obtained from the XRD data show that the Bi-(2223) phase gradually transforms into the Bi-(2212) phase with increasing W substituting for Cu. In addition, from the magnetization measurements at the temperatures below the zero resistance temperatures of the samples, we have observed that a decreasing in magnitude of |M| with the increasing measurement temperature and W concentration. Therefore, the decreasing of |M| related to superconducting volume seems to imply an existence of flux-pinning centers in our samples.     

Phase Relations in the Bi–(Pb)–Sr–Ca–Cu–Sc–O System

The phase relations in the Bi–(Pb)–Sr–Ca–Cu–Sc–O system were studied near Bi₂Sr₂CaCu₂O_{8 +} (Bi-2212) and (Bi,Pb)₂Sr₂Ca₂Cu₃O_{10 +} (Bi-2223) between 850 and 930°C. The introduction of Sc led to the formation of a new compound Sr₂ScBiO₆, which coexisted with Bi-2212 and Bi-2223. Using crystallization from a peritectic melt at different cooling rates, we obtained Bi-2212 matrix composites containing finely dispersed Sr_1.9Ca_0.1ScBiO₆inclusions, with T _cattaining 89 K. The T _cof the Bi-2223–Sr_1.9Ca_0.1ScBiO₆superconducting ceramic prepared by solid-state sintering of a Bi–(Pb)–Sr–Ca–Cu–Sc–O precursor was 108.5 K.     

Structural, superconducting and mechanical properties of molybdenum substituted Bi1.8Sr2Ca1.1Cu2.1Oy

The effect of MoO₃ addition on the properties of Bi-2212 superconducting ceramic samples prepared by solid state reaction method has been investigated. Mo content was varied from 0 to 0.25 on a general stoichiometric formula Bi_1.8Sr₂Mo_xCa_1.1Cu_2.1O_y. Electrical resistivity showed that transition temperature width increased directly with the Mo amount. XRD data have shown that MoO₃ addition in the Bi_1.8Sr₂Mo_xCa_1.1Cu_2.1O_y precursor reduces the amount of Bi-2212 phase. In addition, J_c values of the samples, calculated from the hysteresis loops using the Bean’s model, decreased with increasing Mo substitution. Vickers microhardness measurements show that samples are very sensitive to Mo content and applied load. In addition, various models like Meyer’s Law and Young’s Modulus equations have been used to better explain the mechanical properties of samples.     

Possibilities for formation of the 110 K phase 2223 in Sb or V doped Bi-Sr-Ca-Cu-O and Bi-Pb-Sr-Ca-Cu-O materials

Superconducting oxide materials with nominal composition Bi_2–x Sb _x Sr₂Ca₂Cu₃O_y (x=0.05–0.3) and Bi_1.6Pb_0.4–x V _x Sr₂Ca₂Cu₃O_y (x=0.1 0.4) were synthesized. It was found that after prolonged synthesis, formation of the 2223 phase in the Bi-Sb-Sr-Ca-Cu-O system is possible. However, the critical temperatures of the samples are around 90 K and are lower than those of the superconducting materials from the Bi-Pb-Sr-Ca-Cu-O and Bi-Pb(Sb)-Sr-Ca-Cu-O systems. It was also found that V inhibits the formation of the phase 2223, raises the resistance of the samples and has a negative effect on theT _c and the phase composition of the Bi-Pb(V)-Sr-Ca-Cu-O materials.     

Superconductive and Magnetic Properties of Bi2Sr2Ca2Cu3O10+�� Ceramics Doped by Pb

Among the superconducting phases of bismuth-based Bi?CSr?CCa?CCu?CO, compound Bi₂Sr₂Ca₂Cu₃O_10+?? (Bi-2223) is the most interesting because of its relatively high critical temperature (T _C =95?C110 K) and numerous applications. However, this phase is also known for its low stability and the difficulty of purifying parasites phases including the Bi-2212. To this end, the Pb used in relatively high proportions can stabilize, purify, and improve the further enhancement of T _C . The influence of Pb on structural, superconducting and magnetic properties has been extensively investigated in polycrystalline Bi_2?x Pb _x Sr₂Ca₂Cu₃O_10+?? ceramics (0<x<1). For low Pb amounts, structural analysis shows that the Bi-2223 phase is difficult to achieve without the Bi-2212 phase, and for high Pb content a large fraction of secondary phases containing Pb is detected. Our results confirm that the optimal Pb content for obtaining a Bi-2223 single phase is x=0.3, 0.4.     

Enhancement of (Bi,Pb)-2223 HTS Formation by Boron-Doping

Influence of boron-doping on the superconducting properties of (Bi,Pb)-2223 HTS ceramics prepared in an alumina crucibles has been investigated. X-ray diffraction, resistivity, and AC susceptibility measurements were performed on the undoped and boron-doped compounds. Obtained results have shown that B₂O₃ addition in the Bi_1.7Pb_0.3Ca₂Sr₂Cu₃O _y precursor enhances the formation of high-T _c phase. The boron-doped samples with starting composition Bi_1.7Pb_0.3Ca₂Sr₂Cu₃B _x O _y (x=0.05 and 0.5) reveal significant improvement in the zero resistivity temperature compared to the undoped sample (from 72 K up to 100 K). Boron-doping level x=1.5 results in a substantial degradation of the (Bi,Pb)-2223 phase.     

Superconductivity in nearly single-phase Bi-Pb-Sr-Ca-Cu-O samples with different nominal compositions

The preparation conditions, phase composition, and superconducting properties of Bi-Pb-Sr-Ca-Cu oxide materials from different nominal compositions have been investigated. Nearly single-phase samples from Bi₂Pb_0.4Sr₂Ca₃Cu₄O _y , as well as from the proposed compositions Bi_1.8Pb_0.4Sr₂Ca₃Cu₄O _y and Bi_1.8Pb_0.4Sr₂Ca_2.5Cu_3.5O _y were obtained by a solid-state reaction in air. Samples with the third nominal composition showed the best superconducting properties (T _on=111 K and zero resistance atT ₀=103 K). A possible mechanism for the 2223 phase formation in the three investigated compositions has been discussed.