Strain tolerant microfilamentary conductors of Bi2Sr2Ca1Cu2O(8-delta)

A highly strain-tolerant family of conductors has been developed for the high-temperature superconductor Bi2Sr2Ca1Cu2O(8-delta) by fabricating a microfilamentary composite in which discontinuous filaments of the superconductors are separated from one another by very thin layer of Ag. The Ag provides a region of plastic flow and the strain tolerance. The Ag also provides barriers to supercurrent flow and to overcome these barriers, long slender filaments of Bi(2212) are arranged to have enormous overlap areas perpendicular to the direction of average current flow. This requires filament length to diameter ratios of about 10,000 to 1 Ab barrier thicknesses on the order of 20 nm. This permits high J(c) values even though the sample has a dense array of barriers. At 4.2 K and 0.3 T, critical current densities typically fall smoothly from 1000 to 800 A/sq cm as the strain increases from 0 to 1.6 percent. (Author)