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

摘要

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 (ρ-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, T_c~(onset), T_c~(offset) 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.