INFLUENCE OF THE SURFACE-ROUGHNESS ON CRITICAL CURRENT-DENSITY OF THE BI-PB-SR-CA-CU-O SUPERCONDUCTIVE THIN-FILMS

Bi-Pb-Sr-Ca-Cu-O superconductive films (T(c) greater-than-or-equal-to 100 K) were obtained by annealing films A (Bi + Pb) 1.47SR1.00 Ca0.92Cu1.80O(x) at 850-degrees-C which were prepared by rf-magnetron sputtering using multi-targets. The critical current density (J(c)) of the annealed films was greatly influenced by the surface roughness of the film. J(c) increased proportionally with a decrease in surface roughness, indicating that the decrease of J(c) was caused by the rough surface of the film, and by a liquid phase formed during the annealing process. To avoid the formation of the liquid phase and to obtain smooth surface films, low Ca content films B ( (Bi + Pb) 1.27SR1.00 Ca0.76Cu1.37Ox) were prepared and annealed at a low temperature (835-degrees-C). The surface of the annealed film B was smoother than that of the annealed film A. The obtained films with smooth surface films showed high J(c) (= 27,000 A/cm2) at 77 K in zero magnetic field.