Preparation and Properties of Low‐Calcium‐Content Superconductive Thin Films in Bismuth Systems.

Superconductive, polycrystalline thin films from Bi systems with low Ca content in relation to the high-[Tc] phase and with various Bi(Pb) contents were obtained by two-step annealing of the deposited amorphous films prepared by rf magnetron sputtering. The obtained films, A, B, and C, exhibited a high [Tc] ([Tc] [gt] 100 K) for a wide range of secondary annealing temperatures. The critical current densities of these films at 77.3 K in zero magnetic field were sensitive to the secondary annealing temperature. The highest critical current densities of the films were 2,700, 3,900, and 5,500 A/cm[sup 2] for films A, B, and C, respectively. Film B exhibited large decreases in critical current density under an applied magnetic field. The grain boundaries of this film, which were composed of PbO, CuO, and Bi[sub 2]O[sub 3], apparently acted as weak links in the superconductor materials.