The crystal chemistry of superconducting Sr3.66Bi0.28Ca6.02Cu16.45O28.63 and nonsuperconducting Sr5.97Ca3.13Y0.53Al0.25Bi0.12Cu16.66O28.64 compounds

Abstract

The title compounds from the family of the [M2Cu2O3]5[CuO2]7-type cuprates were synthesized by the flux growth method in the system SrCO3-CaO-Bi2O3-CuO. The crystal structures of Sr3.66Bi0.28·Ca6.02Cu16.45O28.63 (SC) and Sr5.97Ca3.13Y0.53Al0.25Bi0.12·Cu16.66O28.64 (non-SC) were determined. SC: Space group F222, a=11.319(2) Å, b=12.763(2) Å, c=19.491(12) Å, Z=4, R=0.0811 based on 802 reflections with F>4 σ (F). Non-SC: Space group F222, a=11.346(3) Å, b=12.996(3) Å, c=19.585(9) Å, Z=4, R=0.0769 based on 736 reflections with F>4 σ(F). The first crystal (SC) is superconducting (Tc=80K). The structural differences for two compounds in questions have been established: the Cu-Cu distances from the Cu atoms of a ladder plane to the Cu atoms of the ribbons and the bond distances from Cu to the apical oxygen at the plane of the Cu-O ribbons are smaller in the SC compound as compared with those in the non-SC phase.