Research on MgB2 bulk superconductors exposed to Ag nanoparticles diffusion

Uzumcu

2022

J Supercond Nov Magn

In this detailed study, the changes of microstructural, mechanical, and superconducting features of bulk Bi1.8Pb0.2Sr2.0Ca1.8Pb0.2Cu3Oy materials prepared at different milling time intervals (0.5 h ≤ x ≤ 8 h) were investigated in the most precise manner. The measurements of X-ray powder diffraction (XRD) and Vickers microhardness (Hv) were designed to scrutinize the bulk BSCCO samples. All the results of the measurements and calculations show that the characteristics responsible for the applications of the technology, industry, and engineering are significantly improved up to the 3 h milling time beyond that they tend to deteriorate. The enhancement of the characters is generally related to the transition from underdoped level of the (Bi, Pb)-2223 to the optimum level with the milling duration and this event approves that sufficient Pb nanoparticles penetrate the crystal structure. On the other hand, some of the reasons for the suppression in the superconducting properties are the presence of the porosity, disorder, defects, and the localization problem in the Cu-O2 consecutively stacked layers. In addition to those mentioned above, the other reasons are degradation in the crystallinity, reduction in the average crystallite size, and decrease in mobile hole concentration in the Cu-O2 layers. Similarly, the Pb inclusion rises the artificial random dislocations and grain boundary weak-links in the (Bi, Pb)-2223 superconducting system. Vickers microhardness measurements show that (Bi, Pb)-2223 bulk superconducting specimens exhibit typical indentation size behavior depending on the presence of both elastic and plastic deformations in the system. The results obtained from the hardness measurements have been analyzed by using Meyer law, PRS model, MPRS model, elastic–plastic deformation model, and Hays-Kendall approach. As a result, the Hays-Kendall approach was identified as the most successful model in describing the mechanical properties of the samples.

Section: Introductionmentioning

confidence: 99%

Improving Superconductivity, Microstructure, and Mechanical Properties by Substituting Different Ionic Pb Elements to Bi and Ca Elements in Bi-2223 Superconductors

Uzumcu

2022

J Supercond Nov Magn

“…The twin field size is reduced, and a "tweed" pattern is formed by means of arbitrarily distributed Fe +2 ions or Fe +2 clusters as fixation centers for twin interfaces. Ga or Co inclusions for Cu change the structure of the "chain" layer [10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

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

J. Mod. Mech. Eng. Technol.

Uzumcu

2022

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.

“…Especially Vickers hardness testing is one of the most appropriate method for estimating the mechanical properties. Hardness is the mechanical parameters associated powerfully with the structure and the composition of the solid [7].…”

Section: Introductionmentioning

confidence: 99%

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

J Mater Sci: Mater Electron

Terzioğlu

Pakdil

et al. 2015

In this comprehensive work, we focus sensitively on the changes of microstructural, electrical, superconducting and mechanical properties belonging to the bulk Bi 1.7 Pb 0.4 Sr 2.0 Ca 2.0 Zr x Cu 3.1 O y materials with the different Zr nanoparticles (0 B x B 1.0) inserted in the superconducting matrix. The characterizations of the materials prepared are experimentally performed by bulk density, dc resistivity (q-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 Zr 4? ion and 87 pm for Cu 2? 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 ZrO 2 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.