Effect of Pb-doping and annealing on the structure and Tc of Bi-2212 phase superconductor

摘要

A systematic study of Pb-doping and annealing effects in vacuum (2x10(-3) Pa) on Tc and microstructure of Bi2-xPbxSr2CaCu2Odelta compounds has been carried out. It is found that the structure belongs to Bi-2212 phase. The c and b axes almost keep unchanged while Bi is replaced by Pb. With annealing temperature increasing, c and b axes parameters monotonously increase while the a-axis parameter is unchanged. There is an optimum Tc with annealing temperature increasing which reveals that the carrier concentration p changes from overdoped to underdoped. Ii is suggested that a charge-transfer between carrier group (BiO-SrO) and conducting CuO2 plane is induced by Pb-doping and annealing in vacuum. The change of the microstructure and superconductivity of Pb-doped Bi-2212 phase is related to the charge transfer. [References: 6]