STRUCTURAL MODULATION AND HOLE CONDUCTIVITY OF THE HIGH-T-C SUPERCONDUCTOR BI4SR4CACU3O14+X

The modulated structure of the high-T-c superconductor Bi4Sr4CaCu3O14x has been determined in the commensurate approximation utilizing sing le-crystal X-ray diffraction data. The modulation displacement functio ns of the atoms have been obtained by means of harmonic analysis of th e modulation displacements. It has been shown that the topology of the BiO layers, the modulation of the structure and the form of the modul ation displacement functions can be explained by the shifts of the oxy gen atoms in the BiO layers correlated according to the antiferro-elec trical law. The vacancies in the Sr positions provide the hole conduct ivity in the copper-oxygen planes and lead to the formation of the per colation network. (C) 1997 Elsevier Science B.V.