Microstructure of Pb-modified Bi-Ca-Sr-Cu-O superconductor

The microstructure of samples with and without Pb addition has been characterized by transmission electron microscopy. An amorphous Pb-rich grain boundary phase has been found in Pb-doped samples. It is suggested that a Pb-rich liquid phase assists sintering and homogenization of the composition of the superconducting phase to attain the higher zero Tc. In both samples, Ca replacement by Bi has been found. The implications of such a replacement are briefly discussed.