Effect of Compaction Pressure on the $\mathbf {J_c}$ of Superconductor Bi-2212 in Bulk

Abstract

The aim of this work was to study the effect of compaction pressure on the growth of the crystalline structure of the Bi-2212 phase and on the current density of the material. Ceramic samples were prepared by conventional solid-state reaction method, sintered at 840 $^\circ$C after compacting at five different pressures that were 300, 450, 600, 750, and 900 MPa. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), resistivity vs. temperature ($\rho$ vs. $T$) by the four-point probe method, critical current density vs. magnetic field ($J_c$ vs. $H$) at 4 K, and by mass density vs. pressure ($\rho _m$ vs. $P$). The XRD patterns show the main reflections of the Bi-2212 and Bi-2223 phases for all samples, varying slightly in intensity and with the presence of approximately 95.77% and 4.23% of each phase. The highest critical temperature values, at the beginning of the superconductor transition, $T_{c,on1}$, and for $R = 0$, $T_{c,0}$, are noted to be about 111.63 K and 101.20 K, respectively. For the calculations of critical current density, we used the Bean model, obtaining $6.84 x 10^7$ $Am^{-2}$ (the highest for 600 MPa) and $9.71 x 10^6$ $Am^{-2}$ (the lowest for 300 MPa). The optimal conditions that improve the electrical, physical, and morphological behavior of the Bi-2212 superconducting material occur when the compaction pressure is 600 MPa and the lattice parameter $c$ of the crystal structure is increased.