CRYSTAL STRUCTURE AND SUPERCONDUCTIVITY OF Bi2Sr2CaCu2O8 COMPOUND

Abstract

The crystal structure of the ideal compositional compound Bi2Sr2CaCu2O8 with superconducting transition temperature Tc(0)=81.4K has been determined by X-ray powder diffraction method. The basic structure of this compound has the tetragonal symmetry with the lattice constants a=3.825Å, c=30.82Å. The most possible space group is [Formula: see text]. Each unit cell contains two chemical formulae. The arrangements of atoms in the unit cell are as follows: 2Ca cations occupy 2(a) equivalent point position 4Sr, 4Bi and 4Cu cations occupy the same equivalent point position 4(e) with respective parameters z=0.1, 0.3, 0.45. 16O anions respectively occupy 8(g) (z=0.45) and two 4(e) equivalent point positions (z=0.2 and z=0.385). The crystal structure of Bi2Sr2CaCu2O8 can be derived from Aurivillius type structure. The other possible superconducting phases in the Bi-Sr-Ca-Cu-O system can be considered as the structure having different stacking on the basis of Aurivillius phase.