Contact resistance and V-I characteristics in a Ag-doped Bi-Sr-Ca-Cu-O superconductor

Contact resistance and V - I characteristics were investigated in Ag-doped and undoped Bi-Sr-Ca-Cu-O bulk samples prepared by the floating-zone method. In undoped samples, with increasing current pulse width, rapidity of voltage rise in V - I characteristics increases and J c decreases. The contact resistance is nonohmic and temperature dependence is semiconductorlike. In a Ag-doped sample, rapidity of voltage rise and J c are not influenced by pulse width, and deviation of J c among samples is small. The ohmic contact resistance has metallike temperature dependence, and its value is less than 1/500 of that in an undoped sample.