Work instability and its influence on the critical current density of silver sheathed Bi2223 tapes

The characteristic microstructure which develops during the preparation of silver sheathed Bi2223 tapes by the powder-in-tube method is explained. The critical current density (J c ) increases with decreasing tape thickness. During reduction of the thickness, densification and texturing of the microstructure takes place. However, due to the heavy reduction, the degree of variation of oxide layer thickness becomes abruptly large, while J c degrades. This phenomenon is called work instability. A correction of J c that eliminates the influence of work instability has been successfully carried out from a statistical viewpoint.