MECHANICAL PROCESSING OF HIGH J(C) BSCCO SUPERCONDUCTORS

High J(c) superconducting oxides can be obtained by processing polycrystalline powders to achieve high degrees of densification and sharp crystallographic textures characterized by the conducting crystallographic planes lying parallel to the direction of the current flow (i.e., in the plane of a conducting tape or parallel to the axis of a wire). In the present study, we investigate the densification and texture evolution in a Pb doped Bi-Sr-Ca-Cu oxide (BSCCO) under axisymmetric and plane strain (channel die) compression. Experimental measurements of the microstructural evolution, including crystallographic texture and grain morphology, are presented as a function of the degree of deformation and densification. The orientations of the conducting planes (c planes) are shown by measured X-ray pole figures and analyses of these orientations are given for both tests. A model based on crystal plasticity theory is proposed to simulate the inelastic deformation and texturing of the BSCCO oxide. Predicted textures, under both axisymmetric and plane strain compression, agree well with the experimental observations. Analysis of the predicted orientation distribution of the c planes with respect to the loading direction suggests that the most desirable texture for a high overall critical current density can be obtained by axisymmetric compression, but textures that should lead to high J(c)'s are also obtained through plane strain compression.