Crystal Structure of the High-Tc Phase in the Pb-Bi-Sr-Ca-Cu-O System

Abstract

The crystal structure of the high-T _c phase (T _c∼107 K) in the Pb-Bi-Sr-Ca-Cu-O system has been analysed by the Rietveld method on the basis of the X-ray powder diffraction data. The crystal structure belongs to the space group Bbmb and its lattice parameters are a=5.407(6) Å, b=5.407(6) Å and c=37.051(7) Å. The crystal structure is quite similar to that of the high-T _c phase (T _c∼125 K) of Tl₂Ba₂Ca₂Cu₃O₁₀. A flat Cu-O plane and two zigzag Cu-O planes are sandwiched between two Bi-O planes in the crystal structure. It was found that Pb atoms occupy the Bi, Sr and Ca sites by 9%, 7% and 3%, respectively.