Abstract
Critical current density and its history effect in Bi-based high-Tc superconducting tapes were measured by ac inductive method in various magnetic fields and temperatures. A rapid decrease in the critical current density with elevating temperature and the history effect were observed in the same low temperature region between 4.2K and 30K. The coincidence suggests that the two phenomena are caused by “low temperature weak links” in specimens. Weak link region is considered to lose superconductivity at temperature higher than 30K. Above 30K, strongly bonded area retains superconductivity and Jc changes slowly with increasing temperature showing no history effect.
