抄録
The sintering behavior and superconducting properties of the high Tc phase in the Bi(Pb)-Sr-Ca-Cu-O system were investigated using the starting powder with a composition Bi1.8Pb0.4Sr2.0-Ca2.0Cu3.2Oy, which was added to by 0.10mol or 0.15mol of MgO, CaO, SrO and BaO each, then pressformed at 2000kg/cm2 or 5000kg/cm2 and sintered at 850°C or 860°C for 120hr. The influence of the CaO additive was examined in detail in the range of x=0.0-0.7 for Bi1.8Pb0.4Sr2.0Ca2.0+xCu3.2Oy. Bulk densities of 4.8-4.9g/cm2 were obtained in the oxide added systems that were press-formed at 5000kg/cm2 and sintered at 850°C, while Tc was nearly constant at 107-111K. Jc measured at 77K ex-ceeded 500A/cm for both the MgO and CaO added systems. With increasing additive content (x) the bulk density of the above CaO additive system decreased from 4.8 to 4.lg/cm2 at 850°C and from 4.7 to 4.3g/cm2 at 860°C. Tc(zero resistance) increased with increasing x, suggesting that the amount of the coexisting low Tc phase was decreased. The Jc(77K) value increased with x and attained a maximum of 1100A/cm2 at x=0.4 sintered at 850°C and at x=0.6 sintered at 860°C, 4-5 times higher than that of x=0.0.
