Properties and Structure of the F-doped (Bi, Pb)-Sr-Ca-Cu-O Superconductor

Using transmission electron microscopy, x-ray photoelectron spectroscopy, infrared, positron annihilation, and differential specific-heat measurements, we have studied the properties and structure of the F-doped (Bi,Pb)-Sr-Ca-Cu-O superconductor. The results show that the fluorine atoms are homogeneously distributed in the superconducting phase and substituted for the oxygen atoms at O(2) crystallographic sites; the Pb-F and Cu-F bonds are formed. F-doping results in the variance of the incommensurate modulation structure, the increase of the point defects and chemical pressure, the enhancement of the flux-pinning effect, and the change of the electronic structure and chemical bond, and greatly improves the superconductive properties of the 2223 phase of (Bi,Pb)-Sr-Ca-Cu-O.