Volume Fraction Of high-Tc Phase Research Articles

The Effect of Tungsten Nanoparticles on Superconducting of The Compound Bi2-xPb0.3WXSr2Ca2Cu3O10+δ

By using a conventional solid-state reaction technique, a group of the superconducting samples with nominal composition Bi2-xPb0.3WxSr2Ca2Cu3O10±δ with (0≤x≤0.5) sintered at 840ᵒC for 140h in the air have been prepared. The effect substitution of tungsten nanoparticles on the physical properties of Bi sites was studied. X-ray diffraction (XRD) studies showed that all our samples are polycrystalline with orthorhombic structures and presence two phases: high-Tc phase (2223), low-Tc phase (2212) and an impurity phase Some impurities likeSr2Ca2Cu7Oδ, CaO and WO . In the prepared samples the lattice parameter values and the volume fraction of high-Tc phase are calculated. Electrical resistivity measurements show that the values of critical temperature Tc increase with tungsten content. The highest transition temperature, Tc, obtained for Bi2-xPb0.3WXSr2Ca2Cu3O10+δ composition was 191.8K with x=0.3.

Synthesis and characterization of PbO–CdO nanocomposite and its effect on (Bi,Pb)-2223 superconductor

A PbO–CdO nanocomposite-added Bi1.6Pb0.4Sr2Ca2Cu3O10 ((Bi,Pb)-2223) superconductor has been prepared. The effect of the PbO–CdO nanocomposite addition on the transport critical current density (Jc) of (Bi,Pb)-2223 superconductor was investigated. The transition temperature (Tc−onset), zero electrical resistance temperature (Tc−R=0), and Jc of the samples were measured by the four-probe method. Phase formation, structure, and microstructure of samples were investigated. The distribution of nanoparticle size was determined. The results indicated that the PbO–CdO-added samples showed larger grain size and an increased volume fraction of high-Tc phase (Bi-2223) compared to the non-added sample. A slight increase in Tc−R=0 of x = 0.15 wt% was observed. Jc of the PbO–CdO nanocomposite-added samples was significantly higher than for the non-added sample. That could be explained by the possibility that the PbO–CdO nanocomposite acts as an effective flux pinning center in (Bi,Pb)-2223. At 77 K, Jc of x = 0.15 wt% added sample was more than 20 times larger than Jc of the non-added sample (x = 0 wt%). A combined effect of enhanced flux pinning, increased fraction of high-Tc phase and improved grain size, which led to increase in the Jc of added samples, is discussed.

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 Bi1.7−xPb0.3NbxSr2Ca2Cu3Oy (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 (Jc) 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 Bi1.7−xPb0.3NbxSr2Ca2Cu3Oy superconductor. Critical onset (T c on ) and loss peak temperatures (Tp) 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 (Jc) 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-Tc 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 effect of neutron irradiation on the properties of Tl0.6Pb0.3Cd0.1Ba2Ca2Cu3O9-? superconductors

The effect of neutron irradiation on phase purity, crystal structure, and electrical resistivity of Tl_{0.6}Pb_{0.3}Cd_{0.1} Ba_2Ca_2Cu_3O_{9-delta} superconductors has been studied before and after irradiation by electrical resistance measurements and X-ray diffraction techniques. The zero-resistance superconducting transition temperature, T_{c(offset)}, of samples systematically decreases by about 5 K with the increase of neutron irradiation fluence up 18.12 \times 10^{10} n cm^{-2}. The crystalline phases showed that the compounds have 2 phases, a high-Tc phase (1223) and low-Tc phase (1212), in addition to the impurity phase. The irradiation led to a decrease in oxygen content and volume fraction of high-Tc phase (1223).