Effect of Ba-doping on the superconductivity of Bi(Pb)-Sr-Ca-Cu-O

We have prepared Ba-doped Bi(Pb)-Sr-Ca-Cu-O superconductor by a solid-state reaction. The sample compositions used were Bi1.84Pb0.34Sr1.91-xBaxCa2.03Cu3.06Oy with different Ba content of x=0, 0.1 and 0.2, respectively. After calcination followed by presintering, the samples were sintered in air at 820-860°C for 50 h. The superconducting property of the obtained samples was greatly affected by doped-Ba content and the sintering temperature. The X-ray diffraction showed the growth of an almost-single phase with a high-Tc superconducting phase. The crystal quality improved, but the temperatures with the superconducting transition were noticeably suppressed by Ba-doping. The c-axis lattice constant slightly increased with Ba-doping. This fact indicated that Ba was probably incorporated into the Sr site of the crystal structure.