Effect of Heat Treatments and Zr Doped on Superconducting Properties of Bi1.6Pb0.4Sr2Ca2Cu3O ?? Ceramics

The effects of heat treatments and the role of Zr have been studied using X-ray diffraction (XRD) method and resistance measurement technique equipment for the structural identification and determination of critical temperature, T _C. Generally, all samples displayed a normal metallic behavior above T _Conset. The values of T _C(R=0) have been found to decrease as Zr concentration increases. Heat treatments at 830 and 860???C; however, have increased the critical temperature, T _C in samples x=0.15 and x=0.20. The volume of the 2223-phase ratio on 2212-phase has decreased gradually toward Zr concentration. However, for samples x=0.15 and x=0.20, the ratio of 2223-phase was improved after applying heat treatment processes. The crystallographic structure remains in a tetragonal form where a=b??c. A?few Zr is still existed in sample x=0.15 and x=0.20 although after sintering and heat treated at 830???C implies that the excess Zr cannot incorporate into the crystalline structure of BSCCO system. After the heat treatment process at 860???C, all these Zr peaks suddenly disappeared, and hence improved the volume of 2223-phase.     

Superconducting Properties of Ag and Sb Substitution on Low-Density YBa2Cu3O δ Superconductor

The effects of silver (Ag) and antimony (Sb) substitution on low-density YBa₂Cu₃O _δ (YBCO) superconductor were investigated. Two series of sample with a nominal composition of YBa_2?x Ag _x Cu₃O _δ and YBa_2?x Sb _x Cu₃O _δ where x=0.05, 0.10, 0.15, 0.20, 0.30, 0.40 and 0.50 were synthesized and characterized. All Ag-doped samples showed metallic behavior at the normal state and T _C?onset was found at 90 K. T _C?zero decreased as the Ag concentration increased. Optimum Ag concentration was achieved at x=0.20 where T _C?zero has the highest value of 87 K and J _C at 70 K is 16.50 A/cm². For Sb-doped case with x≤0.30, the samples showed metallic behavior above T _C?onset while semiconducting behavior was shown for x≥0.40. The optimum Sb concentration was achieved at x=0.15 where T _C?zero is 85 K and J _C value measured at 70 K is 2.75 A/cm². T _C?onset and T _C?zero were found to decrease toward higher Sb concentration. The crystallographic structure transformed to tetragonal in Sb-doped samples of x≥0.30 while other samples remain orthorhombic.     

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.     

Effect of Al Substitution on Structural and Electrical Properties of Bi1.6Pb0.4Sr2CaCu2−x M x O8+δ Superconducting Ceramics

In this work we study the effect on structural and electrical properties of superconducting compound Bi_1.6Pb_0.4Sr₂CaCu_2?y M _y O_8+δ were M=Al (with y=0–0.6). The samples were prepared by the solid-state reaction method. The samples have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), direct current (DC) resistivity versus temperature ρ(T) and alternative current (AC) susceptibility measurements. Structural analysis shows that the crystalline lattice structure of the prepared sample belongs, mainly, to the superconductive tetragonal phase Bi(Pb)2212. The SEM micrographs show that in the undoped sample the grain size has a random distribution with few grains greater than 5 μm. The grains are very dense and well connected. A quite different microstructure is obtained for the doped samples of which grains are more connected with a flat characteristic shape of Bi(Pb)2212 superconductors. All samples exhibit a superconducting character and T _c and the superconducting volume fraction decrease with increasing rate of aluminum.     

Effect of Sintering Temperature on the Glassy Precursor Synthesis of Superconducting Bi1.6Pb0.4Sr2Cu4Ca3O12+δ

Glassy route synthesis provides homogeneous and dense products of bismuth perovskite superconductors compared with the conventional solid-state sintering technique. Accordingly an attempt has been made here to synthesize Bi_1.6Pb_0.4Sr₂Cu _n Ca _n?1O _w , where n=4 through this route. Instead of varying Bi and Sr, the amount of Ca and Cu has been increased at their sites, in order to improve the superconducting phase assemblage and reduce the impurity. The activation energy for crystallization is evaluated and is found to be equal to 215 kJ/mol. The melt temperature is selected in such a way to reduce the evaporation of Bi and Pb. Analysis of the compositions revealed that the relative amount of Bi increased at the cost of Ca, which has shown a tendency to decrease. It is seen that the relative increase of bismuth in the quenched sample helped in reducing the processing temperature for the formation of superconducting phases. 540 cm^?1 observed in the Raman spectrum of bismuth cuprates has been assigned to the modulated non-superconducting grain through this study.     

The Effect of Cadmium Substitution on the Superconducting Properties of Tl1−x Cd x Ba2Ca2Cu3O9−δ Compound

In order to study how Cd substitution for Tl changes, the superconducting properties of Tl_1?x Cd _x Ba₂Ca₂Cu₃O_9?δ compound with x=0, 0.1, 0.2 and 0.3. We have prepared samples with Cd in place of Tl by the solid state reaction method. It has been found that the increase of the Cd concentrations of all samples produced increases the transition temperature from 113 to 123 K and changes the mass density ρ _m, C/a and volume fraction V _Ph(1223).. XRD shows that the partial substitution of Tl with Cd is helpful to form the superconducting 1223 phase (TlBa₂Ca₂Cu₃O_9?δ ). It has been shown that samples mainly contain tetragonal phase 1223 with a few additional mixed 1212 and 1201 phases.     

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.     

Influence of Sn and Bi Additions on the Structures and Wear Properties of Cu–Sn–P–Ce cBN Tools

In this work Sn and Bi were added to Cu–Sn–P–Ce for improving its microstructures and properties. Structures of the three matrices were investigated by XRD, SEM and EDS. The Cu₄₁Sn₁₁ became the main microstructure with some pores, the grinding ratio increased, and the grinding efficiency improved slightly with the addition of Sn to Cu–Sn–P–Ce. Bi was distributed in the form of simple substance, the grinding ratio increased, and the grinding efficiency greatly reduced with the addition of Bi to Cu–Sn–P–Ce.     

Effect of Bi content on spalling behavior of Sn–Bi–Zn–Ag/Cu interface

The effect of the Bi content on the formation of intermetallic compounds (IMCs) layers between the Sn-xBi-0.9Zn-0.3Ag lead-free solder (with x = 1, 2, 3 and 4, in weight percent, hereafter) and Cu substrate was investigated. The structure of the IMC layer in the soldered interface varies apparently with increasing the Bi content. When the Bi content is 1 wt%, the interface soldered is consisted of CuZn and Cu₆Sn₅ IMC layers, which are separated by an intermediate solder layer. As the Bi content increases, the spalling phenomenon tends to disappear. Moreover, the layer between the Sn-2Bi-0.9Zn-0.3Ag solder and Cu substrate is thicker than others. The evolution of the soldered interfacial structure could be attributed to the existence of Bi.     

Effect of Mn on the Surface Morphological Properties of (Bi, Pb)2 Sr2Ca2Cu3?x Mn x O10+δ (Bi-2223) Superconductor

Samples of (Bi, Pb)₂Sr₂Ca₂Cu_3?x Mn _x O_10+?? (Bi-2223, x=0.0 to 0.30) were synthesized by a solid-state reaction route. The surface morphology investigated through scanning electron microscopy and atomic force microscopy (SEM and AFM) as a result shows that voids and grain sizes increase as the Mn concentration increases, and besides, nanosphere-like structures occur on the surface of the Mn-doped Bi-2223 sample. For x=0, compact granular structures of variously shaped thin grains and larger pores are observed in some local region. In the three-dimensional (3D) AFM view of the same surface the formation of the humps and roughness in some places can also be clearly seen, which is due to the formation of an oxide layer with different thicknesses, depending on the chemical composition of the phases. Besides the said features, two types of inhomogeneity have been observed in our investigations such as, first type, planar nanogranules of various sizes and, second type, closely packed planar rounded nanogranules.     

Mechanical Properties of Bi1.6Pb0.4Sr1.8Ba0.2Ca2Cu3?x Ni x O10+δ Superconducting System

Samples of Bi_1.6Pb_0.4Sr_1.8Ba_0.2Ca₂Cu_3?x Ni _x O_10+?? were prepared by solid-state reaction methods. Mechanical properties (Vickers microhardness, Young modulus, yield strength, fracture toughness and surface energy) by Vickers microhardness measurements have been carried out to examine the effects of Ni substitution. The results showed a deterioration of the mechanical properties with the enhancement of Ni content.     

Improvement of Superconducting Parameters of Bi1.8Pb0.4Sr2Ca2Cu3O10+δ Added with Nano-Ag

Bi_1.8Pb_0.4Sr₂Ca₂Cu₃O_10+δ superconductor samples were synthesized by the conventional solid-state reaction technique. Nano-Ag was introduced by small weight percentages (0.2, 0.4, 0.6, 1, and 1.5 weight %) in the final step of the synthesis process. Phase formation and microstructure were investigated using x-ray powder diffraction, differential scanning calorimetry, and scanning electron microscopy. The real elemental-content and oxygen-content were examined using particle induced X-ray emission (PIXE) and Rutherford backscattering (RBS) techniques, respectively. Electrical resistivity as function of the temperature was carried to evaluate the relative performance of samples. Moreover, Electric field-Current density (E–J) characteristic curves were measured at 77 K. The electrical and granular properties were greatly enhanced, indicating more efficient pinning mechanisms. An improvement of the critical current density of 229 % was obtained with x=0.6 wt.%, while the superconducting transition temperature is improved by 2.5 %.     

Effect of addition of Al and Cu on the properties of Sn–20Bi solder alloy

This study investigates the effect of the composite addition of Al and Cu on the microstructure, physical properties, wettability, and corrosion properties of Sn–20Bi solder alloy. Scanning electron microscopy and X-ray diffraction were used to identify the microstructure morphology and composition. The spreading area and contact angle of the Sn–20Bi–x (x?=?0, 0.1 wt% Al, 0.5 wt% Cu, and 0.1 wt% Al–0.5 wt% Cu) alloys on Cu substrates were used to measure the wettability of solder alloys. The results indicate that the alloy with 0.1 wt% Al produces the largest dendrite and the composite addition of 0.1 wt% Al and 0.5 wt% Cu formed Cu₆Sn₅ and CuAl₂ intermetallic compounds in the alloy structure. And the electrical conductivity of Sn–20Bi–0.1Al is the best, which reaches 5.32 MS/m. The spread area of the solder alloy is reduced by the addition of 0.1 wt% Al and 0.5 wt% Cu, which is 80.7 mm². The corrosion products of Sn–20Bi–x solder alloys are mainly lamellar Sn₃O(OH)₂Cl₂ and the corrosion resistance of 0.1 wt% Al solder alloy alone is the best. The overall corrosion resistance of Sn–20Bi–0.1Al–0.5Cu is weakened and the corrosion of solder alloy is not uniform.

     

Fermi Surface and Superconducting Gap of Triple-Layered Bi2Sr2Ca2Cu3O10 + δ

We present a comprehensive study performed with high-resolution angle-resolved photoemission spectroscopy on triple-layered Bi₂Sr₂Ca₂Cu₃O_{10 +} single crystals. By measurements above T _C the Fermi surface topology defined by the Fermi level crossings of the CuO₂-derived band was determined. A hole-like Fermi surface as for single and double-CuO₂ layered Bi-based cuprates is found, giving new input to the current debate of the general Fermi surface topology of the high-T _C superconductors. Furthermore, we present measurements of the superconducting gap of Bi-2223 and show that there are clear indications for a strong anisotropy of the superconducting gap. The universal properties of this phase in comparison to the other Bi-based cuprates will be discussed.     

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.     

Effect of ZrO2 Addition on Microstructure, Transport and Magnetic Properties of Bi2Sr2CaCu2O8+δ System

The influence of zirconium (Zr) addition to the Bi₂Sr₂CaCu₂O_8+δ (Bi2212) system on its phase formation, microstructure, transport, and magnetic properties is investigated. Samples have been characterized by means of X-ray diffraction analysis (XRD), scanning electron microscopy equipped with energy dispersive of X-ray analysis (SEM/EDX), and resistivity versus temperature measurement. The results show an increase of the critical temperature of superconductive transition T _c for x=0.01 and in all the samples containing Zr the Bi2212 phase is the majority. SEM observations show whiskers grains randomly distributed and microstructural change due to the addition of Zr. Resistivity measurement show that the temperature of the onset of transition T _c increases by 9 K for x=0.005, 0.02, and 5 K for x=0.01 of ZrO₂. An improvement of the normal state conductivity is obtained for the lowest content of Zr (x=0.005). In the normal state, all the samples exhibit a metallic behavior except the sample with x=0.01, which exhibit a semiconductor character.