The crystal chemistry of superconducting Sr(3.66)Bio(0.28)Ca(6.02)Cu(16.45)O(28.63) and nonsuperconducting Sr5.97Ca3.13Y0.53Al0.25Bi0.12Cu16.66O28.64compounds

The title compounds from the family of the [M2Cu2O3](5)[CuO2](7)-type cupra tes were synthesized by the flux growth method in the system SrCO3-CaO-Bi2O 3-CuO. The crystal structures of Sr3.66Bi0.28 . Ca6.02Cu16.45O28.63 (SC) an d Sr5.97Ca3.13Y0.53Al0.25Bi0.12 . Cu16.66O28.64 (non-SC) were determined. S C: Space group F222, a = 11.319(2) Angstrom, b = 12.763(2) Angstrom, c = 19 .491(12) Angstrom, Z = 4, R = 0.0811 based on 802 reflections with F > 4 si gma(F). Non-SC: Space group F222, a = 11.346(3) Angstrom, b = 12.996(3) Ang strom, c = 19.585(9) Angstrom, Z = 4, R = 0.0769 based on 736 reflections w ith F > 4 sigma(F). The first crystal (SC) is superconducting (T-c = 80 K). The structural differences for two compounds in questions have been establ ished: the Cu-Cu distances from the Cu atoms of a ladder plane to the Cu at oms of the ribbons and the bond distances from Cu to the apical oxygen at t he plane of the Cu-O ribbons are smaller in the SC compound as compared wit h those in the non-SC phase.