Quantitative description of the micro structure and its relationship to the critical current density of Ag-sheathed Bi(2223)

By refining the etching technique and subsequent graphic processing, the contiguity, relative alignment and thickness of grains in Ag-sheathed Bi(2223) tape were evaluated from a cross-sectional electron micrograph. Graphic processing was achieved by digitization, inversion and skeletonization of each grain, followed by a description of the two-dimensional distribution of the three-forked crossings ('switches') and the grain thickness. A simple quasi-linear relation between the switch density and the critical current density, J_c, was observed, indicating the significance of the grain contiguity.