抄録
Bi-Pb-Sr-Ca-Cu-O superconducting films were prepared on single MgO substrate by sol-gel method . As the starting solution, we used acetates-solutes butyric acid with the addition of aqueous ammonia . The films were prepared by repeating the process of coating and decomposition (at 700 C for 30 min) 3 or 5 times and by finally sintering at 855°C. for 12h . In the composition of BiaPbbSr2.0Ca2.2Cu3.2Oy (M=a+b, b=0.3a), M was changed 2.6, 2.8, 3.0, 3.2 and 3.4 and it was found that the optimum composition was M=3.2, and when the high-Tc phase amounted to 67% and Tc0 (the critical temperature of zero resistance) = 93 K . As a reason of the existence of optimum M value, there was evaporation of Bi and Pb components which brought about impurities such as (Sr, Ca)2CuO3 for small M(≤2.8) . On the other hand for large M (≥3.0), it gave rise to precipitation of impurities such as CuO. We used Atomic Force Microscope (AFM) in observing surface microstracture, and we could find the height difference without sputtering gold in SEM observation.
