Relationship between microstructure and critical parameters in high Tc superconducting Bi  Pb  Sr  Ca  Cu  O thick films

Abstract

The structural, electrical and magnetic properties of screen-printed superconducting BiPbSrCaCuO thick films have been investigated. The films were either solid state sintered or first melt processed and then annealed over a long period of time. The films were primarily made up of the 2223 phase. The solid state sintered films had randomly arranged flaky crystals. The melt processed films were strongly textured with the (001) planes of the large plate-like grains parallel with the film surface. A pulse method was utilized for critical current measurements, which had the advantage of excluding the effect of local heating of the samples while at the same time increasing the sensitivity of measurement. The magnetic properties of both the solid state sintered and melt processed films were similar, but the transport critical parameters of the melt processed films were superior; the best films having their T c at 105 K and a critical current density of ≈ 2000 A cm −2 at 77 K in a zero external magnetic field. Variation of annealing procedures resulted in clearly different microstructures, which in turn manifested itself in differing superconducting properties. From the point of view of applications, the melt texturing process seems to be promising.