BENDING STRAIN STUDY OF BI-2223 AG TAPES USING HALL SENSOR MAGNETOMETRY/

The influence of room temperature bending on critical current (I-C) of Bi-2223/Ag tapes is studied by Hall sensor magnetometry, four-point m ethod and scanning electron microscopy. Hall sensor magnetometry allow s us to assess tape homogeneity and the amount of mechanical damage ca used by bending. The microstructure of the Bi-2223 ceramic is found to strongly affect the tape behavior under bending strain, In a tape wit h moderate I-C=6.1 A at 77 K and a porous ceramic core, crack propagat ion took place normal to the Ag-ceramic interface, whereas in tapes wi th dense core, I-C above 10 A at 77 K, cracks propagated in the tape p lane, In monofilamentary tapes core homogeneity correlated with good b ending strain performance. In multifilamentary tapes crack propagation between filaments was prohibited by the Ag matrix, thus leading to en hanced strain tolerance, In the high I-C tapes studied, bending to 25 mm radius resulted in 1%-2% I-C degradation.