Contribution To Superconductivity Of Different Ionic Pb Nanoparticles Placed In The Bi-2223 Superconducting System During Different Milling Duration

N. K. Sartekin

Physikalisches Institut — Experimentalphysik II, Universität Tübingen,
Auf der Morgenstelle 14D-72076 Tübingen, (GERMANY)

PAGE NO: 67-82

ABSTRACT – DOI: https://dx.doi.org/10.47204/ACI.1.2.2021.67-82

In this exhaustive study, (Bi_1.8Pb_0.2)Sr₂(Ca_1,8Pb_0.2)Cu₃O_10+δ (Bi-2223) was prepared using a solid state reaction routine and was milled with balls in glass cup rotated by machine at different milling duration ranging from 0,5 h to 8h before sintering. The prepared specimens were characterized by typical experimental methods such as X-ray powder diffraction (XRD), dc resistance (ρ-T), critical current density, scanning electron microscopy (SEM) and bulk density. The electrical and superconducting properties were scrutinized using electrical resistivity and transport critical current density. Structural phase identifications and microstructural features were made by means of X-ray powder diffraction, bulk densty and SEM analysis. This research explores the causes of being higher T_c and higher critical current density in BSCCO superconductor. The results show that the best milling time interval is 3 hours for the highest superconducting transition temperature Tc and the highest transport critical current density Jc because of having stronger c-axis alignment of Bi-2223 and a high proportion of the Bi-2223 phase. More specifically, based on dc resistance and transport critical current density measurements, the Pb⁺² and Pb⁺⁴ inclusions up to optimum level allows better localization in Bi-2223 crystal structure as a result of the arrangement in the dynamics of electron-electron interaction. Thus, the room state conductivity, T_c^onset, T_c^offset and J_c values increase significantly from 0,5 h to 3 h milling duration due to the improvement of crystal structure. On the other hand, when the mixing time is longer than the milling time of 3 hours, the Pb foreign impurities embedded in the Bi-2223 crystal structure instantaneously strengthen the artificial random defects, dislocation and grain boundary weak interactions in the repeatedly stacked layers and especially deform the superconducting Cu-O₂ layers. In addition, XRD research including evidence of the increase in c-axis length up to the optimum mixing time confirms that the superconductivity properties improve with the Pb contribution up to optimum level. On the other hand, the mixing time higher than 3 hours gives rise to the decomposition of the Bi-2223 phase into the Bi-2212 phase and impurities.