V-I properties and n-value of degraded Bi-2223/Ag superconducting tapes

V-I properties of degraded Bi-2223/Ag superconducting tapes were investigated. Samples with cracks and different bending diameters (D) were prepared. Their V-I curves were measured. It was found that defects caused by the bending strain, cracks would influent the n-value of the tape and cause changes in the shape of the V-I curves. Therefore, n-value can be used to evaluate the tape's quality. For low temperature applications far below 77 K, the quality control of the tape is very important, because the defect regions become more dangerous in this case.