The Successful Incorporation of Nd Into Ba Site of Y0.9Ho0.1Ba2-yNdyCu3O7-δ Bulk Superconductors

Abstract: This inclusive study reports the effect of the Nd atoms on the mechanical, microstructural, electrical and superconducting characteristics of Y0.9Ho0.1Ba2-yNdyCu3O7-δ superconductors with the aid of standard characterization methods, including X-ray diffraction, scanning electron microscopy, the bulk density, dc resistivity, and transport critical current density. The experimental results such as the degree of granularity, hole localization effect, room temperature resistivity, critical transition temperature, degree of the broadening, thermodynamic fluctuations, crystallinity, crystal plane alignments, crystal structure, grain size, phase purity and lattice parameters, the appearance of flux pinning centers, grain boundary weak-links, surface morphologies elemental compositions and distributions belonging to Y-site Ho and Ba-site Nd substituted Y-123 superconducting samples are discussed in detail for the first time. All the experimental findings show that the microstructural, electrical, mechanical and superconducting properties regularly improve with the increment in the HcN (Ho constant+Nd changeble) until a certain value of y=0.100, beyond which the characteristics tend to retrograde rapidly. This is attributed to the fact that excess penetration of the Nd damages the crucial properties given above

Solubility limit of tetravalent Zr nanoparticles in Bi-2223 crystal lattice and evaluation of fundamental characteristic properties of new system

In this comprehensive work, we focus sensitively on the changes of microstructural, electrical, superconducting and mechanical properties belonging to the bulk Bi1.7Pb0.4Sr2.0Ca2.0ZrxCu3.1Oy materials with the different Zr nanoparticles (0 a currency sign x a currency sign 1.0) inserted in the superconducting matrix. The characterizations of the materials prepared are experimentally performed by bulk density, dc resistivity (rho-T), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), electron dispersive X-ray (EDX) and Vickers microhardness (H (v) ) investigations. It is found that all the characteristics given above (especially superconducting properties) degrade considerably with the increment in the Zr addition level, and in fact they reach to the global minimum points in case of the maximum dopant level. The main reason of the rapid decrement in the electrical and superconducting properties stems from the presence of the localization problem in the Cu-O-2 consecutively stacked layers. Likewise, the Zr foreign addition increases the artificial random defects, dislocations and grain boundary weak-links in the superconducting system, even being favored by the SEM examinations. At the same time, the EDX surveys indicate that the Zr nanoparticles in the tetravalent state prefer to substitute for the divalent states of the Cu inclusions through the crystal structure as a result of their close ionic radius values (86 pm for Zr4+ ion and 87 pm for Cu2+ ion). Thus, the differentiation of the electronegativity reduces the mobile hole concentration in the Cu-O-2 slabs. Additionally, the XRD experimental findings show that there is a systematic decrement in the Bi-2223 (high) phase up to the Zr concentration level of x = 0.70 beyond which new characteristics peaks of ZrO2 appear immediately. This is in relation to the fact that the solubility limit corresponding to the Zr foreign impurity in the Bi-2223 system is about x = 0.70. Similarly, the regular decrement in both the c-axis length and crystallite size with the dopant confirms the deterioration of the superconducting properties. Furthermore, the dramatic reduction of the H (v) values stems from the suppression of the crystallinity and connection quality in the intergrain coupling of the superconducting samples exhibiting typical Indentation Size Effect behavior due to the existence of both elastic and plastic deformations in the system

Decrement in metastability with Zr nanoparticles inserted in Bi-2223 superconducting system and working principle of hybridization mechanism

This exhaustive study experimentally deals with the role of Zr foreign impurities on the electrical, superconducting and flux pinning properties of the bulk Bi-2223 superconducting compounds by the typical experimental characterization methods such as dc resistivity (rho-T), transport critical current density (J (c) ) and powder X-ray diffraction (XRD) surveys. All the experimental findings show that the curial characteristics, being in charge of the varied attractive and feasible applications, retrograde significantly with the enhancement of the Zr nanoparticles in the Bi-2223 superconducting system due to the presence of two trap levels for mobile holes. This leads to the degradation of the metastability of the superconducting materials. In more detail, based on the dc resistivity and transport critical current density measurements, the Zr additives give rise to the localization problem as a consequence of the change in the dynamics of electron-electron interaction. Thus, the room state conductivity, , and J (c) values retrograde significantly. Similarly, the Zr foreign impurities embedded in the Bi-2223 crystal lattice make the artificial random defects, dislocations and grain boundary weak-interactions in the consecutively stacked layers enhance immediately, and the superconducting Cu-O-2 layers distort especially. Moreover, the XRD investigations including the evidences about the decrement/increment in the c-axis/a-axis length verify the regression of the superconducting properties with the Zr dopant. The main differentiation of the lattice constant parameters stems from aliovalent substitutions (replacement of the divalent Cu by the tetravalent Zr impurties) along with the crystal structure. In other words, the reduction of the electronegativity leads to decrease the mobile hole concentration in the Cu-O-2 consecutively stacked layers. Furthermore, all the decrement parameters are theoretically favored by hybridization mechanism.https://doi.org/10.1007/s10854-015-3839-

Important defeats on pinning of 2D pancake vortices in highly anisotropic Bi-2212 superconducting matrix with homovalent Bi/La substitution

Yildirim, Gurcan/0000-0002-5177-3703; saritekin, namik kemal/0000-0002-0759-0598WOS: 000350388800019This comprehensive study aims to investigate the change of the flux pinning mechanism, electrical and superconducting properties of the inorganic solid Bi-2212 materials with the La inclusions inserted in the crystal structure by means of magnetotransport measurements exerted in the applied magnetic field range of 0-7 T. Crucial characteristics as regards critical transition temperatures (T-c(onset) and T-c(offset)), room temperature resistivities (rho(300K)), residual resistivities (rho(0)), residual resistivity ratios (RRR), irreversibility fields (mu H-0(irr)), upper critical fields (mu H-0(c2)), thermodynamic critical fields (mu H-0(c)), activation energies (U-0), penetration depths (lambda) and coherence lengths (xi) are evaluated from the experimental magnetoresistivity curves and available theoretical approaches. All the properties obtained above confirm the considerable degradation in the pinning of 2D pancake vortices with the increment of the La individuals randomly distributed in the Bi-2212 superconducting system. Thus, the improved recoupling linelike nature among the consecutively stacked layers leads to decoupling of the adjacent layers and suppression of the interlayer Josephson coupling length as a result of the enhancement in the thermal fluctuations of flattened pancake vortices. The long and short of it is that the La impurities undermine the elasticity of the vortex lattice. For example, the T-c(offset) and T-c(onset) values are found to be about 84.5 K and 85.7 K for the best (pure) sample while the material exposed to the La content level of x = 0.2 obtains the values of 82.2 K and 15.1 K, respectively at zero applied magnetic field. In the case of the applied magnetic field of 7 T, the T-c(offset) value reduces considerably towards the lower temperature values of 72.6 K for the former compound. However, the values belonging to the worst sample (La4) cannot be determined at higher external magnetic field value such as 1 T due to the hybridization of La-3/states with the Cu3d-O2p states in the Cu-O-2 layers (dissipation). This is attributed to the existence of the pair-breaking mechanism in Bi-site La substituted Bi-2212 systems. Moreover, the flux pinning energy values calculated from thermally activated flux flow (TAFF) model decrease dramatically with the enhancement of both the La content level and external magnetic fields. Numerically, the activation energy value is calculated to be about 5173 K (1077 K) for the pure sample at the field value of 0 T (7 T) whereas the values pertaining to the compound substituted by the La concentration level of x = 0.15 are found to be in a range of 1196-281 K. The lack of the experimental evidences does not enable us to find the energy values belonging to the La4 sample at higher applied field. As for the critical field parameters (mu H-0(c1), mu H-0(c), mu H-0(irr), mu H-0(c2) and mu H-0(c3)) and the extracted values (lambda, xi and kappa), the changes in the parameters given also verify the degradation of the flux pinning ability (random distribution of the artificial pinning centers) with the La concentration as a result of the Cooper pair-breaking mechanism. To sum up, the La impurities are unfavorable for the potential applications of these materials in the commercial sector at high temperatures and magnetic fields. (C) 2015 Elsevier B.V. All rights reserved.Abant Izzet Baysal University Scientific Research Project Coordination UnitAbant Izzet Baysal University [2013.09.03.655]This study is partially supported by Abant Izzet Baysal University Scientific Research Project Coordination Unit (Project No: 2013.09.03.655)

Improvement of Mechanical Characteristics and Performances with Ni Diffusion Mechanism Throughout Bi-2223 Superconducting Matrix

This study is interested in the role of diffusion annealing temperature (650-850 degrees C) on the mechanical characteristics and performance of pure and Ni diffused Bi-2223 superconducting materials by means of standard compression tests and Vickers hardness measurements at performed different applied loads in the range of 0.245-2.940N and theoretical calculations. Based on the experimental findings, the mechanical performances improve with increasing annealing temperature up to 700 degrees C beyond which they degrade drastically due to the increased artificial disorders, cracks and irregular grain orientation distribution. In other words, the penetration of excess Ni inclusions accelerates both the dislocation movement and especially the cracks and voids propagation as a result of the decrement in the Griffith critical crack length. Further, it is to be mentioned here that all the sample exhibit typical indentation size effect (ISE) behavior. In this respect, both the plastic (irreversible) and elastic (reversible) deformations have dominant role on the superconducting structures as a result of the enhancement in the elastic recovery. At the same time elastic modulus, yield strength and fracture toughness parameters are theoretically extracted from the microhardness values. Moreover, the elastic modulus parameters are compared with the experimental values. It is found that the differentiation between the comparison results enhances hastily with the increment in the applied indentation test loads due to the existence of the increased permanent disorders, lattice defects and strains in the stacked layers. Namely, the error level increases away from the actual crystal structure. Additionally, the microhardness values are theoretically analyzed for the change of the mechanical behaviors with the aid of Meyer's law, elastic/plastic deformation and Hays-Kendall approaches for the first time