Vacuum heat treatment effect on the thermophysical properties of BSCCO system

Vacuum heat treatment effects at 850 °C for (3, 6, 9 and 12 h) on the crystalline structure and superconducting, as well as on the mechanical properties of Bi4Sr3Ca3Cu6Ox (BSCCO) have been studied. The highest critical transition temperature Tc 102 K was achieved at annealing time tann = 9 h. This maximum value is attributed to movement of excess oxygen from annealed sample. Phase examination by X-ray diffraction (XRD) revealed that the gradual formation of the high-Tc phase (2 2 2 3) due to the prolongation of annealing time up to 9 h. Thereafter, the high-Tc phase starts degrading and Tc reduces. The distortion of the 2 2 2 3 phase is suggested by the broadening of the different XRD peaks. Also, at the same above annealing time (9 h), SEM observation shows good quality plate-like crystal with relatively oriented. On the other hand, the Vickers microhardness (VHN) measurements was found to be dependent on the annealing conditions, a tremendously increase of VHN value 1.92 GPa (0.25 N) at tann = 9 h. This substantial increase is ascribed to improvement of the thermal conduction and stabilization of temperature distribution between superconducting grains.