Synthesis and characterization of Bi-2212 superconductors under low pelletization pressure with different dwell times

In this thesis, the superconducting properties of the Bi-2212 phase in the BiSrCaCuO (BSCCO) superconductor family, which change with the application of different residence times under low pelletization pressure, were investigated. For this study, the Bi-2212 phase of the BSCCO family was preferred because it has the most stable thermodynamic structure. In this study, Bi-2212 ceramics were prepared using the conventional solid state reaction method and different residence times ranging from 12 hours to 72 hours were applied at a constant pelletization pressure of 114 MPa during the pressing stage. It was seen from the XRD plots that all samples had high Bi-2212 phase. In addition, only Bi2CaO4 phase was detected as the secondary phase. Even though this applied pelletization pressure was chosen low according to the literature, due to its high thermodynamic stability, the formation of a high rate of Bi-2212 phase occurred in all samples. SEM results showed that all samples had similar grain morphology with random grain orientation and homogeneous phase formation, except that all samples had different grain sizes. The Tc values obtained from the M-T (magnetization-temperature) curve for all samples are in the range of 77-82 K, showing that the Bi-2212 phase is formed at ideal ratios. The magnetic properties of the prepared samples were investigated by M-H (Magnetic hysteresis) and magnetic Jc curves (critical current carrying density calculated within the framework of the Bean model) at 15 K. In this study, it was found that a 12 hour dwell time under 114 MPa constant pelletization pressure provided the best superconductivity properties and the highest Jc values (1.605 x 104 A/cm2 at T=15 K and H=1.5 T) for the Bi-2212 phase. In addition, the nailing force density (Fp) was calculated from the Jc and B values to better examine the flux nailing properties of the samples. The maximum nailing force (3.929 Oe A/cm2, T= 15 K and H= 1.95 T) was obtained in the sample subjected to a holding time of 12 hours under 114 MPa.