The role of post-annealing process on the physical, electrical and magnetic properties of nano-sized tin substituted Bi-2212 superconducting ceramics

In the present work, post-annealing was applied to Bi2Sr1.80(SnO2)0.2Ca2Cu1.75Na0.25Oy samples prepared by the solid state reaction method at different temperatures of 730 degrees C, 780 degrees C and 830 degrees C for fixed dwelling time. Samples were analysed by XRD, SEM, R-T and M-H measurements. In XRD results, it was determined that despite the decomposition of the Bi-2212 phase after the post-annealing, the major phase in all samples was Bi-2212 phase. In the SEM measurement results, plate-like grain formation was observed in the microstructures of all samples. With the increase of post-annealing temperature, the sizes of plate-like grains decreased due to the decomposition in the Bi-2212 superconducting phase. In R-T graphs, an increase in the Tc was obtained in the sample with 730 degrees C post-annealing. In the M-H plots of all samples, hysteresis loop was obtained as the characteristic behaviour of Bi-2212 high transition temperature superconductors. Jc values were calculated from Bean model. In the sample with 830 degrees C post-annealing, as a result of the development of flux pinning centres, 1.219 X 106 A/cm2 of Jc value was obtained. Pinning Forces (Fp) were measured from Jc and B. In the sample with 830 degrees C post-annealing, the development of flux pinning mechanisms can be assisted by the secondary phases that arise from the decomposition of the Bi-2212 phase, leading to an increase in Fp.