BiPbSrCaCuO superconductor prepared by a three-step reaction process

A three-step reaction process was proposed to prepare the Bi-system superconductor based on the principles of physical chemistry. High-temperature chemical reactions in the preparation process of the superconductor, high-temperature behaviour of the superconducting phases, superconductivity of the material and the critical current density of Ag-sheathed composite tape were studied. High-temperature chemical reactions were found to obey the principles of metallurgical physical chemistry. Heat treatment temperature and composition were shown to have an important effect on superconductivity and the formation of the high-T_c phase, the 2212 and 2223 phases melted incongruently at 875 and 882 degrees C, respectively, and the liquid phase was found to consist of a 2201 type compound and Cu₄O₃. The best value of critical current density of Ag-sheathed composite tape obtained was over 1.3*10⁴ A cm^-1 (77 K, 0 T).